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  • Articles  (296)
  • NMR  (294)
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  • Springer  (296)
  • Chemistry and Pharmacology  (294)
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  • 1
    Electronic Resource
    Electronic Resource
    Determination of charge density of anionic polyacrylamide flocculants by NMR and DSC (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 812-817 
    Details
    ISSN: 1435-1536
    Keywords: Charge density ; polyacrylamide ; NMR ; DSC ; T g
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract New methods are suggested for the determination of the charge density of acrylamide/acrylate copolymers.13C nuclear magnetic resonance spectroscopy was used to determine the comonomer ratio by comparing the peak intensities of the methine carbon in acrylamide and acrylate monomers. Results were compared with those obtained by conductometric and potentiometric titration and were found to be in good agreement. Differential scanning calorimetry was employed to determine the glass transition temperatures (T g) of the copolymers. A master curve was established by plottingT g versus charge density of the copolymers previously determined by NMR and conductometric titration. Compositions of poly(acrylamide-co-acrylate) samples can thus be determined by measuring theT g and reading the percent composition directly from the master curve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412958
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  • 2
    Electronic Resource
    Electronic Resource
    13C NMR analysis of polyoxyethylenated surfactants — determination of critical micellar concentration (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 667-669 
    Details
    ISSN: 1435-1536
    Keywords: surfactants ; NMR ; micelles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01452460
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  • 3
    Electronic Resource
    Electronic Resource
    NMR investigation of the micellar properties of monoalkylphoshpates (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 489-496 
    Details
    ISSN: 1435-1536
    Keywords: micelle ; NMR ; alkylphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The micellization of several monoalkylphoshpates with chain lenghts from 6 to 10 carbons have been investigated by31P and13C NMR spectroscopy with some additional electrical conductivity, density and small angle neutron scattering measurements. The major part of this study was performed on sodium monooctylphosphate. The critical concentration of micellization is 0.14 M, the partial molar volume is 170 cm3/mole in the micellar state. Small angle neutron scattering measurements on a 0.5 molar solution lead to an aggregation number of 43. NMR studies over the whole concentration range show that the pseudophase model holds. The geometry around the polar head is found almost unchanged upon micellization. The frequency denpendence of the31P longitudinal relaxation is interpreted by an isotropic fas motion (τ R=6.5 × 10−11 for the free monomers and by a strongly anisotropic motion withD ‖/D ⊥≈10 andτ 0=(6D)−1 =1.25×10−9 s in the micellar state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412046
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  • 4
    Electronic Resource
    Electronic Resource
    Diffusion in three and four component microemulsions containing nonionic surfactant studied by pulsed field gradient nuclear magnetic resonance and quasi-elastic light scattering (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 81-86 
    Details
    ISSN: 1435-1536
    Keywords: Microemulsions ; diffusion ; NMR ; QELS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Diffusion studies were performed with various methods to obtain some insight into the structure and the dynamical processes of three and four component microemulsions containing p-nonylphenol ethylene oxide adducts which were mixtures of highly branched p-nonyl isomers with well defined distributions of the ethylene oxide chain length. Diffusion coefficients were determined by pulsed field gradient and pulsed field gradient Fourier transform1 H NMR as well as by quasi-elastic light scattering. The combined application of pulsed field gradient NMR and quasi-elastic light scattering gives information about the critical behaviour of the systems whereas pulsed field gradient Fourier transform NMR allows the determination of the diffusion coefficients of the individual constituents. The results suggest that the very complex three and four component microemulsions studied undergo critical concentration fluctuations in a large temperature region from about 15 °C below the lower critical solution temperatures. The deduced critical exponents are in good agreement with theoretical predictions. The aggregates in the three and four component microemulsions show differences in the self diffusion behaviour of their constituents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411252
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  • 5
    Electronic Resource
    Electronic Resource
    From solvated electrons to metal anions: Electronic structure and dynamics (1985)
    Springer
    Journal of solution chemistry 14 (1985), S. 187-208 
    Details
    ISSN: 1572-8927
    Keywords: Solutions of metals in non-aqueous solvents ; NMR ; ESR ; magnetic susceptibility ; solvated electrons ; ion-pairs ; solvated atoms ; metal anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The techniques of magnetic susceptibility and magnetic resonance (NMR, ESR) have proved to be invaluable in the study of the electronic structure and dynamics of both paramagnetic and diamagnetic species in solutions of metals in non-aqueous solvents. This paper contains a brief review of recent experimental work in this area, concentrating on localized excess-electron states ranging from solvated electrons, electron-cation encounter species, through finally to ‘gas-like’ metal anion species existing in these non-aqueous solutions. Throughout, the emphasis is on the information gleaned from magnetic measurements about the microstructure and environment of these matrix-bound states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647062
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  • 6
    Electronic Resource
    Electronic Resource
    A hydrogen-1, chlorine-35, and lanthanum-139 NMR coordination study of the lanthanum (III) ion in aqueous solvent mixtures (1989)
    Springer
    Journal of solution chemistry 18 (1989), S. 313-330 
    Details
    ISSN: 1572-8927
    Keywords: La(III) ; hydration ; proton ; NMR ; La-139 ; Cl-35
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A La(III) hydration study has been carried out for solutions of La(ClO4)3 and, in a preliminary way, La(NO3)3 in aqueous mixtures with acetone-d6 and Freon-12, using hydrogen-1, chlorine-35, and lanthanum-139 NMR spectroscopy. Low temperature, proton magnetic resonance experiments allowed the direct observation and area evaluation of separate signals for water molecules in the primary solvation shell of La(III) and in bulk medium. Measurements over a wide range of salt and solvent concentration gave a maximum La(III) hydration number of 6 and no evidence for inner-shell ion-pairing in La(ClO4)3 solutions. Chlorine-35 chemical shift and linewidth data in these solutions confirmed the absence of contact ionpairing. Hydration numbers of 3–4 for La(III) in several La(NO3)3 solutions clearly indicated inner-shell complex formation. Lanthanum-139 chemical shift and linewidth measurements for these systems revealed the presence of some process, possibly hydrolysis, in the La(ClO4)3 solutions at extremely high acetone-d6 concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656771
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  • 7
    Electronic Resource
    Electronic Resource
    Identification of proton type in concentrated sweet solutions by pulsed NMR analysis (1989)
    Springer
    Journal of solution chemistry 18 (1989), S. 795-801 
    Details
    ISSN: 1572-8927
    Keywords: NMR ; Pulse relaxation sugars ; sweetness ; hydration ; protons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The spin-spin proton relaxation times T2 of concentrated sucrose, maltose,D-glucose andL-proline solutions were determined using a Bruker Minispec NMR Spectrometer. Log spin echo amplitude decay curves were also determined and their non-linear nature allowed the proportions of different proton types to be calculated. These were in agreement with the theoretical proportions of ring (non-exchangeable protons), solute hydroxyl protons and water protons in the simple sugar molecules. A deuteration experiment confirmed that only non-exchangeable ring protons remained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651811
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  • 8
    Electronic Resource
    Electronic Resource
    A direct nitrogen-15 NMR study of praseodymium(III)-nitrate complex formation in aqueous solvent mixtures (1993)
    Springer
    Journal of solution chemistry 22 (1993), S. 519-538 
    Details
    ISSN: 1572-8927
    Keywords: Nitrogen-15 ; NMR ; praseodymium-nitrate complexes ; water-acetone mixtures ; contact ion-pairing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A direct, low-temperature nitrogen-15(15N) NMR technique has been applied to the study of inner-shell complex formation between praseodymium(III) and nitrate ion in aqueous solvent mixtures. In water-acetone mixtures at −95°C, ligand exchange is slow enough to permit the observation of15N NMR signals for uncomplexed and coordinated nitrate ion, but satisfactory resolution is obtained only by the addition of Freon-12 to these systems for study at −110 to −115°C. Four coordinated nitrate signals are generally observed and a very small signal for an additional complex, or an isomer of one of the others, appears at the highest nitrate concentrations. Signals for the mono-and dinitrato complexes are unambiguously identified, but with the exception of the trinitrato complex, several possibilities exist for the remaining peaks. To overcome excessive viscosity signal broadening, measurements in methanol and ethanol are possible only with praseodymium trifluoromethanesulfonate (triflate). Coordinated nitrate signals in aqueous and anhydrous methanol are observed only for the mono-and dinitrato species, and signal areas indicate a maximum of two moles of nitrate per Pr(III) are complexed. A third signal is evident in the ethanol solution spectra, and the presence of this higher complex was confirmed by area measurement of the fraction of bound nitrate. The extent of complex formation in these solvent systems is attributed to differences in the dielectric constant. A comparison of the complexing tendencies of Pr(III) to other ions studied by this NMR method suggests the possibility of a coordination number change across the lanthanide series. Preliminary15N NMR results for metal-ion complexes with the isothiocyanate ion are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646929
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  • 9
    Electronic Resource
    Electronic Resource
    Solvent effect on the intramolecular hydrogen bond in 8-quinolinol N-oxide (1996)
    Springer
    Journal of solution chemistry 25 (1996), S. 179-189 
    Details
    ISSN: 1572-8927
    Keywords: Intramolecular hydrogen bond ; solvent effect ; dipole moment ; IR ; UV ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solvent effect on intramolecular hydrogen bond in 8-quinolinol N-oxide has been studied by IR, UV,1H NMR and13C NMR spectroscopy, dipole moment measurements and quantum-mechanical calculations. The solute-solvent interactions are of local character and they vary considerably over the range of solvent under study. The results suggest that formation complexes with solvent molecules weaken the intramolecular hydrogen bond in 8-quinolinol N-oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00972688
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  • 10
    Electronic Resource
    Electronic Resource
    A direct carbon-13 and nitrogen-15 NMR study of samarium(III) complexation with nitrate and isothiocyanate in aqueous solvent mixtures (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 1019-1047 
    Details
    ISSN: 1572-8927
    Keywords: Carbon-13 ; nitrogen-15 ; NMR ; samarium-nitrate complexes ; samarium-isothiocyanate complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The extent of inner-shell, contact ion-pairing between samarium(III)-nitrate and in a preliminary manner, samarium(III)-isothiocyanate, has been determined by a direct, low-temperature, multinuclear magnetic resonance technique. In water-acetone mixtures containing Freon-12 or Freon-22, the slow exchange condition is achieved at −110 to −120°C, permitting the observation of15N NMR resonance signals for bulk and coordinated nitrate. In these mixtures, signals are observed for Sm(NO3)2+, Sm(NO3) 2 + , and two higher complexes, possibly the tetranitrato with either the penta-or hexanitrato.1H NMR signals for bound water molecules in these mixtures were observed, but accurate hydration numbers can not yed be determined. In anhydrous or aqueous methanol mixtures,15N NMR signals for only three complexes are observed, with the dinitrato clearly dominating. Using15N and35Cl NMR chemical shift and linewidth measurements, the superior complexing ability of nitrate compared to perchlorate and chloride, was demonstrated. Successful preliminary13C and15N NMR measurements of Sm3+-NCS− interactions in water-acetone-Freon-22 mixtures also have been made. The13C NMR spectra reveal signals for five complexes, presumably Sm(NCS)2+ through Sm(NCS) 5 2− . In the15N NMR spectra, signals for only three complexes are observed (the result of insufficient spectral resolution.) displaced about +240 ppm from bulk anion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00974101
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  • 11
    Electronic Resource
    Electronic Resource
    Molecular motion and interactions in aqueous carbohydrate solutions. III. A combined nuclear magnetic and dielectric-relaxation strategy (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 33-46 
    Details
    ISSN: 1572-8927
    Keywords: Aqueous ; hydration ; sugar ; carbohydrate ; nuclear magnetic relaxation ; NMR ; dielectric relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A strategy is developed for the complementary use of dielectric and nuclear magnetic relaxation methods to elucidate the molecular dynamics in aqueous solutions of small hydrophilic molecules, and hence determine extents of hydration. The nuclear magnetic relaxation data, as well as characterizing the motional properties of various carbohydrate solutes, is used here to test alternative models for the resolution of the dielectric spectra into their component relaxation processes. This approach results in a much more confident analysis of solvent relaxation properties than has in the past been usual, to yield information relating to the extents of hydration of small sugars and the possible orientation-specific nature of this hydration. It is demonstrated that the dielectric relaxation of the sugar molecules themselves is unequivocally not due to the reorientation of the whole molecule and most likely is dominated by the rotation of hydrate side chain groups (hydroxyls and hydroxymethyl). In proton magnetic relaxation studies of glucose in D2O it is observed that one particular proton (H-1 in the α-form only) is extremely susceptible to inter-molecular proton-proton interactions while the remaining protons are very effectively shielded. This observation is shown to be fully consistent with the conformational and hydration properties of glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647179
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  • 12
    Electronic Resource
    Electronic Resource
    Molecular motion and interactions in aqueous carbohydrate solutions. II. Nuclear-magnetic-relaxation studies (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 17-31 
    Details
    ISSN: 1572-8927
    Keywords: Aqueous ; hydration ; sugar ; carbohydrate ; nuclear-magnetic relaxation ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nuclear-magnetic-relaxation studies of a range of aqueous mono- and disaccharide solutions are reported. These include17O relaxation of solvent and1H,2H,13C, and17O relaxation of various solutes. The limitations of nuclear-magnetic relaxation for providing direct indications of solvent motions or extents of hydration of these sugars are outlined. In contrast to the solvent studies, the motional properties of the solutes themselves have been reasonably well defined, with1H,2H, and13C studies of the sugar ring C−H groups all indicating very similar rotational correlation times. Shorter correlation times estimated for the −CH2OH and −OH side chains, implying that internal motions make a significant contribution to the relaxation of these groups. Differences in reorientation rates of pentose monosaccharides, hexose monosaccharides, and disaccharides are discussed in terms of molecular size and solvent interactions. In every case examined, the solute NMR rotational correlation time is in serious disagreement with that expected from previous dielectric-relaxation studies. Some of the implications of this discrepancy are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647178
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  • 13
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of alternating silane copolymers: (Me2Si−R2Si−Me2Si) n (1995)
    Springer
    Journal of inorganic and organometallic polymers and materials 5 (1995), S. 217-236 
    Details
    ISSN: 1572-8870
    Keywords: Polysilane ; NMR ; pyrolysis ; randomization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bimodal molecular weight distributions of alternating copolymers of the type (Me2Si−R2Si−SiMe2) n , where R=hexyl and butyl, were obtained by polymerization of BrSiMe2−R2Si−Me2SiBr, using the Wurtz coupling method. Analysis of the samples by pyrolysis GC MS and solution29Si NMR indicated that some randomization occurred, due to cleavage of the original Si−Si bonds in the monomer. The extent of randomization was significantly greater in the high molecular weight fractions. Based on the nature of the rings from the py MGC/MS traces and the number on nonads found in the29Si spectra, two types of randomization processes have been proposed, involving backbiting followed by (1) ring expulsion or (2) redistribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01057894
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  • 14
    Electronic Resource
    Electronic Resource
    A direct hydrogen-1 and phosphorus-31 nuclear magnetic resonance cation solvation study of Al(ClO4)3, Ga(ClO4)3, In(ClO4)3, UO2(ClO4)2, and UO2(NO3)2 in water-acetone-dimethylsulfoxide and water-acetone-hexamethylphosphoramide mixtures (1972)
    Springer
    Journal of solution chemistry 1 (1972), S. 433-444 
    Details
    ISSN: 1572-8927
    Keywords: Acetone ; aluminum ; cation ; dimethylsulfoxide ; gallium ; hexamethylphosphoramide ; indium ; NMR ; solvation ; uranyl ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A competitive solvation study of Al(ClO4)3, Ga(ClO4)3, In(ClO4)3, UO2(ClO4)2, and UO2(NO3)2 in water-acetone-dimethylsulfoxide (DMSO) and water-acetone-hexamethylphosphoramide (HMPT) mixtures has been carried out by direct H1 and P31 nuclear magnetic resonance (NMR) techniques. At low temperature, proton and ligand exchange are slow enough in these systems to permit the observation of signals for bulk and coordinated molecules of water and the organic bases (DMSO and HMPT). Both DMSO and HMPT compete effectively with water for coordination sites in the Al3+, Ga3+, and In3+ systems, with steric effects dominating the HMPT results. Both Al3+ and In3+ are able to bind a maximum of two to three HMPT molecules, for example. In contrast, UO2+ is solvated selectively by the organic molecules to the allowed maximum of 4 molecules per cation. H1 and P31 NMR spectral results support the formation of only the mono-, tri-, and tetra-HMPT solvation complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645606
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  • 15
    Electronic Resource
    Electronic Resource
    NMR chemical shifts of xenon in aqueous solutions of amphiphiles: A new probe of the hydrophobic environment (1984)
    Springer
    Journal of solution chemistry 13 (1984), S. 779-787 
    Details
    ISSN: 1572-8927
    Keywords: NMR ; chemical shifts ; aqueous solutions ; alcohols ; xenon ; dimethylsulfoxide ; amphiphiles ; hydrophobic effects ; acetonitrile ; dioxane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemical shift of elemental xenon in solution is sensitive to the environment. The shift arises from van der Waals interactions in most liquids, but an additional effect is present in aqueous media yielding a larger shift than expected. In water the shift is affected by the presence of low molecular weight amphiphiles, and its variation with composition can reveal the presence of hydrophobic hydration of the amphiphile. The results are similar to the conclusions drawn from other physical studies. Data are presented for aqueous solutions of methanol, ethanol, n-propanol, iso-propanol, tert-butanol, dimethylsulfoxide, p-dioxane, and acetonitrile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647693
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  • 16
    Electronic Resource
    Electronic Resource
    NMR chemical shifts of xenon in mixed aprotic solvents: A probe of liquid structure (1986)
    Springer
    Journal of solution chemistry 15 (1986), S. 777-790 
    Details
    ISSN: 1572-8927
    Keywords: NMR ; chemical shifts ; mixed solvents ; xenon ; acetone ; alkanes ; carbon tetrachloride ; N,N-dimethylformamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemical shift of elemental xenon is extremely sensitive to the environment. In aprotic solvents, the presence of xenon has little effect on the solvent structure, and preferential solvation is not observed in any mixed solvent system. Consequently, xenon shifts can reveal the presence of short range order in certain liquids. Chemical shift data are presented for several model systems, including mixtures of different alkanes, alkanes with benzene, alkanes with acetone, and carbon tetrachloride with dimethylformamide (DMF). In certain cases, the xenon shift is strongly non-linear with composition. This effect arises from a specific interaction between the two solvents in the CCl4-DMF system, while it reflects short range liquid order in the acetone-alkane systems. This effect is also apparent in the deviation of the densities of the acetone-alkane mixtures from ideality.
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    URL: http://dx.doi.org/10.1007/BF00646718
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  • 17
    Electronic Resource
    Electronic Resource
    NMR study of the stoichiometry, stability and exchange kinetics of complexation reaction between Pb2+ ion and 18-crown-6 in binary acetonitrile-water mixtures (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 63-74 
    Details
    ISSN: 1572-8927
    Keywords: 18-Crown-6 ; lead ; mixed-solvent ; complex stability ; exchange kinetics ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Proton NMR was used to study the complexation reaction between lead ion and 18-crown-6 in a number of binary acetonitrile-water mixtures. Formation constant for the resulting 1∶1 complexes in different solvent mixtures was determined by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability and amount of water in the mixed solvent. The dissociative kinetics of the complex was studied by proton line-shape analysis. The Arrhenius plots showed a distinct isokinetic temperature at about 25°C at which the decomplexation rate is more or less independent of the solvent composition. the complexation rate and the activation parameters E a , ΔH
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    URL: http://dx.doi.org/10.1007/BF00972608
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  • 18
    Electronic Resource
    Electronic Resource
    A direct15N NMR study of erbium(III)-nitrate complexation in aqueous solvent mixtures (1991)
    Springer
    Journal of solution chemistry 20 (1991), S. 893-903 
    Details
    ISSN: 1572-8927
    Keywords: Hydrogen-1 ; nitrogen-15 ; chlorine-35 ; NMR ; erbium nitrate ; complexation ; acetone ; methanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The extent of inner-shell ion-pair formation of Er3+ with nitrate ion in aqueous mixtures has been studied by nitrogen-15 (15N) NMR spectroscopy. At low temperature, exchange is slow enough to permit the direct observation of15N signals for nitrate ions in the Er3+ solvation shell and in bulk medium. In water-acetone mixtures,15N NMR signals for the mono-and bis complexes are observed at low nitrate to Er3+ mole ratios, but only the bis complex is evident at higher anion concentrations. No spectral evidence for the tris complex was seen at any nitrate concentration. In water-methanol-acetone mixtures, signals for the mono and bis complexes persist even at higher nitrate concentrations, indicating a reduced tendency to ion-pair with increasing dielectric constant. Preliminary15N NMR results are presented for the nitrate complexes of other paramagnetic lanthanide ions.
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    URL: http://dx.doi.org/10.1007/BF01074951
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  • 19
    Electronic Resource
    Electronic Resource
    Complex formation of hydronium ion with several crown ethers in 1,2-dichloroethane, acetonitrile, and nitrobenzene solutions (1992)
    Springer
    Journal of solution chemistry 21 (1992), S. 275-288 
    Details
    ISSN: 1572-8927
    Keywords: Crown ethers ; hydronium ion ; complexation ; molar conductance ; ion pairing ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A conductance study concerning the interaction between hydronium ion and several crown ethers in acetonitrile, nitrobenzene and 1,2-dichloroethane solutions has been carried out at 25°C. The stability constants of the resulting 1:1 complexes in acetonitrile and nitrobenzene solutions were determined from the molar conductance-mole ratio data and found to vary in the order 18C6〉DB30C10〉DC18C6〉DB18C6〉DB21C7〉DB24C8〉B15C5. In 1,2-dichloroethane solution, the complexation process results in the dissociation of ion pairs. There is an inverse relationship between the stabilities of the complexes and the Gutmann donicity of the solvents. In nitrobenzene solution, some evidence for the formation of a 2:1 sandwich adduct between the smaller crowns (i.e., B15C5 and 18-crowns) are observed from the molar conductance-mole ratio data which is supported by the1H NMR data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647023
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  • 20
    Electronic Resource
    Electronic Resource
    Direct hydrogen-1, carbon-13, and nitrogen-15 NMR study of magnesium(II)-isothiocyanate complexing (1995)
    Springer
    Journal of solution chemistry 24 (1995), S. 1249-1263 
    Details
    ISSN: 1572-8927
    Keywords: Hydrogen-1 ; carbon-13 ; nitrogen-15 ; NMR ; magnesiumisothiocyanate complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A hydrogen-1, carbon-13, and nitrogen-15 NMR study of magnesium(II)-isothiocyanate complexation in aqueous mixtures has been completed. At temperatures low enough to slow proton and ligand exchange, separate1H,13C, and15N NMR signals are observed for coordinated and bulk water molecules and anions. The1H NMR spectra reveal signals for the hexahydrate and the mono-through triisothiocyanato complexes, as well as two small signals attributed to [Mg(H2O)5(OH)]1+ and [Mg(H2O)4(OH)(NCS)]. Accurate hydration numbers were obtained from signal area integrations at each NCS− concentration. In the15N NMR spectra, signals also were observed for the mono-through triisothiocyanato complexes, and a small signal believed to be due to [Mg(H2O)4(OH)(NCS)]. Coordination number contributions for NCS− were measured from these spectra and when combined with the hydration numbers they totalled essentially six at each anion concentration. Signals for [Mg(H2O)5(NCS)]1+ through [Mg(H2O)3(NCS)3]1− also were observed in the13C NMR spectra and the area evaluations were comparable to the15N NMR results. An analysis of the magnitude and sign of the coordinated NCS− chemical shifts identified the nitrogen atom as the anion binding site. All spectra indicated [Mg(H2O)5(NCS)]1+ and [Mg(H2O)4(NCS)2] were the dominat isothiocyanato complexes over the entire range of anion concentrations. The inability to detect evidence for complexes higher than the triisothiocyanato reflects the competitive binding ability of water molecules and perhaps the decreased electrostatic interaction between NCS− and negatively charged higher complexes.
    Type of Medium: Electronic Resource
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    Nuclear magnetic resonance study of the ligand interchange of Ba2+-18-crown-6 complex in methanol solution (1996)
    Springer
    Journal of solution chemistry 25 (1996), S. 1029-1039 
    Details
    ISSN: 1572-8927
    Keywords: 18-Crown-6 ; barium ; methanol ; exchange kinetics ; bimolecular mechanism ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Exchange kinetics of Ba2+-18-crown-6 complex in deuterated methanol solution was studied by proton NMR line-shape analysis of a series of solutions containing equal population of free and complexed 18-crown-6, but varying concentration of the macrocycle, at various temperatures. From −33 to 37°C, the predominant mechanism for the exchange of the ligand between the two sites is a bimolecular pathway which is characterized by the following activation parameters:E a=47±2 kJ-mol−1; ΔH ≠=45±2 kJ-mol−1; ΔS ≠=−8±4 J-mol−1-K−1. However, the contribution of a dissociative mechanism with activation parametersE a=36±5 kJ-mol−1, ΔH ≠=33±5 kJ-mol−1 and ΔS ≠=104±18 J-mol−1-K−1 becomes more important at higher temperatures.
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    URL: http://dx.doi.org/10.1007/BF00972597
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    A direct hydrogen-1, carbon-13, and nitrogen-15 NMR study of lutetium(III)-isothiocyanate complexation in aqueous solvent mixtures (1996)
    Springer
    Journal of solution chemistry 25 (1996), S. 1071-1082 
    Details
    ISSN: 1572-8927
    Keywords: Hydrogen-1 ; carbon-13 ; nitrogen-15 ; NMR ; lutetium(III) ; isothiocyanate ; complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A direct, low-temperature hydrogen-1, carbon-13, and nitrogen-15 nuclear magnetic resonance study of lutetium(III)-isothiocyanate complex formation in aqueous solvent mixtures has been completed. At −100°C to −120°C in water-acetone-Freon mixtures, ligand exchange is slowed sufficiently to permit the observation of separate1H,13C, and15N NMR signals for coordinated and free water and isothiocyanate ions. In the13C and15N spectra of NCS−, resonance signals for five complexes are observed over the range of concentrations studied. The13C chemical shifts of complexed NCS− varied from −0.5 ppm to −3 ppm from that of free anion. For the same complexes, the15N chemical shifts from free anion were about −11 ppm to −15 ppm. The magnitude and sign of the15N chemical shifts identified the nitrogen atom as the binding site in NCS−. The concentration dependence of the13C and15N signal areas, and estimates of the fraction of anion bound at each NCS−:Lu3+ mole ratio, were consistent with the formation of [(H2O)5Lu(NCS)]2+ through [(H2O)Lu(NCS)5]2−. Although proton and/or ligand exchange and the resulting bulk-coordinated signal overlap prevented accurate hydration number measurements, a good qualitative correlation of the water1H NMR spectral results with those of13C and15N was possible.
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    URL: http://dx.doi.org/10.1007/BF00972922
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    Self-diffusion and electron spin exchange of hydrophobic probes in dilute solution (1975)
    Springer
    Journal of solution chemistry 4 (1975), S. 797-807 
    Details
    ISSN: 1572-8927
    Keywords: NMR ; ESR ; spin exchange ; self-diffusion ; hydrophobic interaction ; nitroxide ; spin probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electron spin exchange rate constants have been measured by ESR spectroscopy for a nitroxide spin probe in a number of solvents, including water. The apparent collision rate constants (k c ′ ) calculated from the spin exchange rate constants showed marked deviations from the Smoluchowsky equation (k c ′ η=const), which were greatest in solvents of lowest viscosity. These effects are attributed to inefficiency of the spin exchange process. Self-diffusion coefficients (D) were measured for diamagnetic analogs of the nitroxide spin probe in similar solvent systems by pulsed field gradient NMR spectroscopy. TheD values gave reasonable agreement when corrected for viscosity (Dη=const). Collision rate constants calculated fromD were in good agreement with those measured by ESR in solvents of high viscosity. Thek c ′ value for the spin probe in water was significantly lower than that in isoviscous organic solvents. This effect is discussed in terms of a hydrophobic hydration shell for the spin probe which acts as an additional barrier to collision.
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    Methionine sulfoxide formation in proteins: NMR study (1990)
    Springer
    BioMetals 3 (1990), S. 125-126 
    Details
    ISSN: 1572-8773
    Keywords: Methionine sulfoxide ; NMR ; Bovine pancreatic trypsin inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary 1H-NMR spectra of bovine pancreatic trypsin inhibitor (BPTI) both native and oxidized by chloramine T, are reported. The spectrum of the oxidized form is characterized by the appearance of two singlets for methyl group shifted 0.60 and 0.46 ppm downfield with respect to the native form.
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  • 25
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    Metabolism-independent binding of toxic metals by Ulva lactuca: cadmium binds to oxygen-containing groups, as determined by NMR (1997)
    Springer
    BioMetals 10 (1997), S. 105-117 
    Details
    ISSN: 1572-8773
    Keywords: BET ; biosorption ; cadmium ; cobalt ; copper ; Freundlich ; NMR ; Scatchard ; Ulva lactuca ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The metabolism-independent metal binding characteristics of Ulva lactuca were investigated using both freeze-dried thalli and cell walls stripped of intracellular material by incubation in Triton-X followed by methanol. Biosorption of Cd, Zn, Cu and Co by freeze-dried thallus was concentration-dependent and followed Freundlich and Langmuir isotherms. The Freundlich plot suggested that freeze-dried U. lactuca had the greatest binding affinity for Cu compared with Cd, Zn and Co. The BET (Brunauer–Emmett–Teller) plot, which indicates a more complex form of adsorption, and the Scatchard plot were not adequate models for Cu adsorption. The Scatchard plot of Cd suggested that two Cd binding sites were available on the freeze-dried thallus, with the second, lower affinity site only becoming available at Cd loading capacities greater than 4.9mmol g dry wt. Cd nuclear magnetic resonance (NMR) studies confirmed that two binding sites were available for Cd on the freeze-dried algal powder, though only one was available on the cell wall, and that the affinity of the binding sites was greater for Cu than for Cd. The results of the NMR experiments suggested that Cd binds to oxygen-containing functional groups in the algal powder and on the cell wall. It is proposed that sulphate or hydroxyl groups attached to polysaccharide subunits are possible sites.
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    URL: http://dx.doi.org/10.1023/A:1018379106700
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    Interaction of Cu(II) 3,5-diisopropylsalicylate with human serum albumin - an evaluation of spectroscopic data (1998)
    Springer
    BioMetals 11 (1998), S. 21-26 
    Details
    ISSN: 1572-8773
    Keywords: copper(II) 3,5-diisopropylsalicylate ; EPR ; human serum albumin ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The copper(II) complex of 3,5-diisopropylsalicylate is a lipophilic water-insoluble binuclear complex, Cu(II) (3,5-DIPS) , that has attracted interest because of a wide range of pharmacological activities. This study was undertaken to examine bonding interactions between the complex and human serum albumin (HSA) to help elucidate the mode of transport of the complex in vivo. Electron paramagnetic resonance, numerical magnetic resonance and UV-visible absorption spectroscopic studies were performed using 200 μM aqueous solutions (pH 7.5) of HSA to which had been added up to three molar equivalents of CuCl , CuSO , or Cu(II) (3,5-DIPS). Both EPR and UV-visible spectra demonstrated the presence of more than one copper bonding site on HSA, and proton NMR spectra showed that the 3,5-DIPS ligand is also bonded to HSA. These results indicate that there is no observable direct coordination of the ligand to copper in the presence of HSA, and that the majority of the copper and 3,5-DIPS bond to HSA at separate sites. Addition of solid Cu(II) (3,5-DIPS) to HSA at pH 7.5 similarly resulted in spectra that suggest that there are no ternary Cu(II)(3,5-DIPS), Cu(II)(3,5-DIPS) , or Cu(II) (3,5-DIPS) complexes formed with HSA. It is concluded that any ternary complexes formed in the presence of HSA are below the spectroscopic detection limits and represent less than 5% of the total copper. © Rapid Science 1998.
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    Interaction of aluminum ion with ATP. Mechanism of the aluminum inhibition of glycerol kinase and its reversal by spermine (1998)
    Springer
    BioMetals 11 (1998), S. 63-67 
    Details
    ISSN: 1572-8773
    Keywords: aluminum ion ; glycerol kinase ; NMR ; spermine ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Aluminum ion inhibited yeast glycerol kinase competitively with respect to the substrate MgATP. The K value of the enzyme for aluminum ion was about 3 μM. Spermine at physiological concentrations prevented glycerol kinase from the inhibition by aluminum ion. Nuclear magnetic resonance spectroscopy showed the specific elimination by spermine of aluminum from the metal-ATP complex, but no dissociation of MgATP complex by spermine. Inhibition by aluminum ion of glycerol kinase as well as hexokinase can reduce the utilization of energy fuel in yeast. Change in polyamine concentration may control energy production in vivo, and is responsible for the development of age-related aluminum toxicity. © Rapid Science 1998.
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    Physical and structural characterization of yersiniophore, a siderophore produced by clinical isolates of Yersinia enterocolitica (1996)
    Springer
    BioMetals 9 (1996), S. 157-167 
    Details
    ISSN: 1572-8773
    Keywords: iron ; siderophore ; Yersinia enterocolitica ; structure ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Clinical isolates of Yersinia enterocolitca, which belong to mouse-lethal serotypes, produce the siderophore yersiniophore. Siderophore production was shown to be iron regulated and to reach maximum production in late log phase. Yersiniophore is a fluorescent siderophore with maximum excitation at 270 nm and a major emission peak at 428 nm. Absorption maxima were seen at 210 and 250 nm with a low broad peak from 280 to 320 nm. Purification of unchelated yersiniophore for structural analysis was made difficult by low yields (1–2 mg mg-1), and susceptibility to acid hydrolysis, oxidation and possibly polymerization. Yersinophore was therefore purified as an Al3+ chelate, which was found to be stable in solution for several weeks. To purify Al3+-yersiniophore, unchelated yersiniophore was first extracted from culture supernatants with dichloromethane, concentrated by rotary evaporation and adsorbed to a DEAE-sephacel column. Al3+-yersiniophore was eluted with 0.01 m AlCl3 and further purified by HPLC. The structure was established by a combination of elemental analysis, high resolution mass spectrometry and two-dimensional NMR experiments. Yersiniophore is a phenolate-thiazole siderophore with the formula C21H24N3O4S3Al and a molecular weight of 505.07404 when chelated to Al3+. The structure of yersiniophore was determined to be closely related to the structures of pyochelin, produced by Pseudomonas aeruginosa, and anguibactin, produced by Vibrio anguillarum.
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    Study of the V2O5-Al2O3 interaction during ultra-high intensity grinding (1992)
    Springer
    Catalysis letters 13 (1992), S. 261-266 
    Details
    ISSN: 1572-879X
    Keywords: Vanadia ; alumina ; grinding ; ESR ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ultrahigh intensity grinding of mechanical mixtures of V2O5 with γ-Al2O3 at ambient temperature was found to create vanadyl complexes with ESR spectral parameters identical to those of vanadia-alumina samples prepared by impregnation methods. No interaction was found after intensive grinding of γ-Al2O3 with V2O4.
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    In situ13C NMR study of tert-butanol interaction with moderately concentrated sulfuric acid (1994)
    Springer
    Catalysis letters 29 (1994), S. 311-323 
    Details
    ISSN: 1572-879X
    Keywords: NMR ; tert-butanol ; sulfuric acid ; carbenium ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An in situ NMR study of tert-butanol dehydration in 95 and 85% sulfuric acid did not indicate the formation of tert-butyl cations as active reaction intermediates. Instead, only NMR lines from oxonium ions under the condition of fast exchange with water and the acid were observed. It is most likely that, in the concentrated acid, the active intermediates of this reaction are represented by tert-butyl sulfuric ester which probably is a precursor of invisible tert-butyl carbenium ions representing short-lived excited or transition states.
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    1H-NMR and relaxometry of copper-containing dimers in proteins (1990)
    Springer
    BioMetals 3 (1990), S. 146-150 
    Details
    ISSN: 1572-8773
    Keywords: Copper ; Cobalt ; Nickel ; Superoxide dismutase ; Alkaline phosphatase ; NMR ; Relaxometry ; Nuclear relaxation ; Electronic relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The water-proton nuclear-magnetic-relaxation dispersion profiles have been analyzed for Cu2Zn2-superoxide dismutase (SOD) and Cu2-alkaline phosphatase (AP). The electronic relaxation times are derived, together with structural information. The effect of magnetic coupling with another copper ion in Cu2Cu2SOD and Cu2Cu2AP is discussed. It is shown that the electronic relaxation times of copper(II) essentially do not change. The opposite happens with Cu2Co2SOD, Cu2Co2AP and Cu2Ni2SOD in which fast-relaxing metal ions provide relaxation mechanisms for copper(II) as well. In these cases the systems can be studied through high-resolution NMR spectroscopy.
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    The effect of flexible lattice aluminium in zeolite beta during the nitration of toluene with nitric acid and acetic anhydride (2000)
    Springer
    Catalysis letters 70 (2000), S. 61-65 
    Details
    ISSN: 1572-879X
    Keywords: flexible lattice aluminium ; zeolite beta ; nitration ; regio‐control ; para‐selectivity ; toluene ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The nitration of toluene with nitric acid and acetic anhydride using zeolite H‐beta as catalyst was studied with multi‐nuclear solid‐state NMR spectroscopy in order to investigate the causes for the observed enhanced para‐selectivity. The reversible transformation of framework aluminium from a tetrahedral into an octahedral environment was observed by 27Al NMR upon interaction of the zeolite with the different components of the nitrating system. The octahedral co‐ordination complex between lattice aluminium and acetylnitrate might explain the surface‐catalysed para‐selective nitration reaction and suggests that the lattice flexibility plays an important role in determining the regio‐selectivity of the nitration catalysed by zeolites.
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    Multinuclear Magnetic Resonance Study of Zinc(II) and Cadmium(II) Complexing with Isothiocyanate (1998)
    Springer
    Journal of solution chemistry 27 (1998), S. 331-359 
    Details
    ISSN: 1572-8927
    Keywords: Hydrogen-1 ; carbon-13 ; nitrogen-15 ; cadmium-113 ; NMR ; infrared ; zinc(II) ; cadmium(II) ; isothiocyanate ; complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A study of zinc(II) and cadmium(II) complexes with isothiocyanate ion has been completed, using a low-temperature, multinuclear magnetic resonance technique that permits the observation of separate resonance signals for bound and free ligand, and Cd(II) metal ion. The Zn2+–NCS− complexes were studied by 1H, 13C, and 15N NMR spectroscopy. In the 1H spectra, the intensity of the coordinated water signal, corresponding to a Zn(II) hydration number of six in the absence of NCS−, decreases dramatically as this anion is added, indicating the complexing process involves more than a simple 1:1 ligand replacement. The 13C and 15N NMR spectra reveal signals for four species, most reasonably assigned to a series of tetrahedrally coordinated Zn2+–NCS− complexes. In the Cd2+–NCS− solution spectra, the 13C and 15N signals for four complexes also are observed and they are three line patterns, corresponding to a doublet from 113Cd J-coupling, and a dominant central peak, resulting from bonding to magnetically inactive Cd isotopes. The 113Cd spectra, showing signals for four complexes, correlate well in all respects with the 13C and 15N results, including coupling in specific cases. The spectral results for both metal ions reflect binding at the nitrogen atom of NCS−, with the complexes changing from an octahedral to a tetrahedral configuration when doing so. Confirming evidence for these conclusions also was provided by several infrared measurements of these metal–ion systems.
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    A Direct Carbon-13 and Nitrogen-15 NMR Study of Samarium(III)–Isothiocyanate Complexation in Aqueous Solvent Mixtures (1998)
    Springer
    Journal of solution chemistry 27 (1998), S. 581-600 
    Details
    ISSN: 1572-8927
    Keywords: Carbon-13 ; nitrogen-15 ; chlorine-35 ; NMR ; samarium(III) ; isothiocyanate ; Sm3+ − NCS− complexes ; water–acetone–Freon ; water–methanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Multinuclear magnetic resonance studies of trivalent lanthanide inner-shell ion-pairing with nitrate and isothiocyanate are continuing. For NCS− solutions in water–acetone–Freon mixtures at low temperature, generally −100 to −125°C, ligand exchange is slow enough to permit the observation of 13C and 15N NMR signals for coordinated and free anions. For samariuni(III) solutions, four coordinated NCS−signals, displaced about +35 ppm and +250 ppm from free anion, are observed in the 13C and 15N NMR spectra, respectively. The 13C and 15N NMR data are complementary, showing a signal area concentration dependence and measured coordination numbers consistent with the formation of Sm(NCS)2+ through Sm(NCS) 4 1 . The coordination numbers reach a maximum of about three moles of NCS− per mole of Sm(III) with both nuclides, a result confirmed by spectral appearance showing the dominance of Sm(NCS)3 at the highest concentration studied. An analysis of the chemical shifts indicates that binding occurs at the nitrogen atom of NCS−. In water–methanol, due to the higher dielectric constant of such mixtures, coordination was less extensive. A competitive binding study with Ci− by 35Ci NMR demonstrated conclusively the superior coordinating ability of NCS−.
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    A Direct Carbon-13 and Nitrogen-15 NMR Study of Cerium(III)–Isothiocyanate Complexation in Aqueous Solvent Mixtures (1999)
    Springer
    Journal of solution chemistry 28 (1999), S. 193-210 
    Details
    ISSN: 1572-8927
    Keywords: carbon-13 ; nitrogen-15 ; chlorine-35 ; NMR ; cerium(III)–isothiocyanate complexes ; water–acetone–Freon ; water–methanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A study of lanthanide complexation with isothiocyanate is underway using a multinuclear magnetic resonance technique. For isothiocyanate solutions in water–acetone–Freon mixtures at low temperature, −85–−125°C, ligand exchange is slow enough to permit the observation of 13C and 15N NMR signals for coordinated and free anions. For the Ce3+–NCS− system, four coordinated anion signals, displaced from the free anion signal by about +450 to +550 ppm for 15N and +50 to +80 ppm for 13C, are observed. The 13C and 15N spectral data are complementary, showing a signal area concentration dependence and measured coordination numbers consistent with the formation of Ce(NCS)2+ through Ce(NCS)1- 4. In water–methanol, the extent of complexing is decreased, presumably because of the higher dielectric constant of this medium. In addition, the results of a competitive study of NCS− and Cl− ion binding, carried out using 35Cl NMR, is presented.
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    A direct nitrogen-15 NMR study of cerium(III)-nitrate complexes in aqueous solvent mixtures (1992)
    Springer
    Journal of solution chemistry 21 (1992), S. 651-666 
    Details
    ISSN: 1572-8927
    Keywords: Nitrogen-15 ; chlorine-35 ; NMR ; cerium nitrate ; complexation ; water acetone mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A study of the complex formation which occurs between cerium(III) and nitrate ions in aqueous solvent mixtures has been carried out by a direct, low-temperature, nitrogen-15 (15N) NMR technique. At temperatures in the range of −95 to −110°C, ligand exchange is slow enough to permit the observation of separate15N NMR signals for bulk nitrate, and this anion in the cerium(III) principal coordination shell. In water-acetone-Freon-12 mixtures, the spectra reveal the nitrato complexes do not form consecutively. Rather, signals are observed for Ce(NO3)2+, Ce(NO3) 2 1+ , and only two other higher order complexes, even at very high NO 3 − to Ce(III) mole ratios. Signal area evaluations were used to identify the possible higher order complexes. At comparable salt concentrations in aqueous-methanol mixtures, only Ce(NO3)2+ and Ce(NO3) 2 1+ are formed, reflecting a decreased tendency for complexation in media of higher dielectric constant.
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    A direct carbon-13 and nitrogen-15 NMR study of europium(III) complexation-nitrate and europium(III)-isothiocyanate complexation in aqueous solvent mixtures (1996)
    Springer
    Journal of solution chemistry 25 (1996), S. 345-367 
    Details
    ISSN: 1572-8927
    Keywords: Carbon-13 ; nitrogen-15 ; NMR ; europium-nitrate complexes ; europium-isothiocyanate complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A direct, low-temperature nuclear magnetic resonance spectroscopic study of europium(III)-nitrate contact ion-pairing has been completed, and preliminary results for europium(III)-isothiocyanate have been obtained. In water-acetone-Freon mixtures, at −110°C to −120°C, four15N NMR signals are observed for coordinated nitrate ion. Area evaluations of the signals and their concentration dependence indicate the formation of Eu(NO3)2+, Eu(NO3) 2 1+ , and two higher complexes, possibly the tetra-, with either the penta-or hexanitrato. This correlates well with similar15N NMR results obtained for Ce(III), Pr(III), Nd(III), and Sm(III). As a result of a higher dielectric constant, complex formation is significantly less in water-methanol mixtures, wheein only three complexes form with Eu(NO3) 2 1+ dominating at the highest anion concentrations. Competitive complexing experiments in water-methanol also were made by35Cl NMR chemical shift and linewidth measurements, as well as15N NMR. Initial experiments with the Eu3+-NCS− system show four coordinated anion signals, displaced from the bulk anion peak by about −250 ppm and −2,500 ppm in the13C and15N NMR spectra, respectively. Area evaluations are consistent with the presence of Eu(NCS)2+ through Eu(NCS) 4 1- in these solutions. A consideration of the chemical shifts identified the nitrogen atom as the site of binding in the NCS−. A discussion of these preliminary results, as well as those for several other metal-ions, will be presented.
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    The effect of pressure and temperature of self-diffusion coefficients in several concentrated deuterium oxide diamagnetic electrolyte solutions (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 563-574 
    Details
    ISSN: 1572-8927
    Keywords: Self-diffusion ; concentrated electrolyte solutions ; high pressure ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pressure dependences of the self-diffusion coefficients of deuterium oxide in 4.5m solutions of LiCl−D2O and CsCl−D2O (also 7m) and 3.06m CaCl2−D2O have been measured by the NMR spin-echo method at 30°C, 60°C, and 90°C. Shear viscosities and densities of these solutions have also been determined over the same range of experimental conditions. The experimental data show that the diffusion constantD decreases with the increasing structure-making ability of the electrolyte cation Ca+2〉Li+. In contrast, the diffusion coefficient for D2O in the 4.5 and 7m CsCl solutions is equal to that for pure D2O at 30°C but lower at 60°C and 90°C. It has been found that the Stokes-Einstein equation relates well the diffusion coefficients to shear viscosity in these concentrated electrolyte solutions.
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    High resolution NMR techniques in catalysis (1998)
    Springer
    Topics in catalysis 5 (1998), S. 133-147 
    Details
    ISSN: 1572-9028
    Keywords: NMR ; catalysis ; high pressure ; dynamic equilibria ; magnetization transfer ; sapphire tube ; gas phase ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract High resolution NMR techniques are applicable to a variety of aspects of catalysis. Methods for studying homogeneously-catalyzed systems under high gas pressure are described along with approaches for obtaining mechanistic and dynamic information. Many of the same techniques may be applied to heterogeneous catalysis by following the reaction chemistry by gas phase NMR.
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    URL: http://dx.doi.org/10.1023/A:1019133515789
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    Dampfdruckmessungen und Protonenresonanzuntersuchung an Hydriden der intermetallischen Phasen Ti2(Ni, Co) und Ti2(Ni, Fe) (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 141-147 
    Details
    ISSN: 1434-4475
    Keywords: Diffusion of hydrogen ; Hydrides of intermetallic compounds ; NMR ; Thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract NMR and hydrogen equilibrium pressure measurements were performed on hydrides of the intermetallic compounds Ti2(Ni, Co) and Ti2(Ni, Fe). The following values of enthalpy ΔH and entropy ΔS for the formation of the hydrides of the intermetallic phases Ti2Co and Ti2Ni were found: ΔH(Ti2CoH y )=−47.6 kJ/mol H2, ΔH(Ti2NiH y )=−53.7 kJ/mol H2; ΔS(Ti2CoH y )=−119.8 J/(K·mol H2), ΔS(Ti2NiH y )=−127.5 J/(K·mol H2). By substitution of Ni or Co by Fe, the values of ΔH and ΔS of the corresponding quaternary hydrides become less negative. An interpretation of the experimental results is tried by the model ofShaltiel and coworkers. Proton diffusion was investigated in a series of the intermetallic hydrides Ti2(Ni, Co)H x and Ti2(Ni, Fe)H x . The diffusion rate is lowered by increased Ni/Fe substitution. Substitution of Ni by Co scarcely effects the “hopping process”. The activation energies were found to be smaller for the Ti2Ni-hydrides compared with the Ti2Co-hydrides.
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    Über Reaktionen von Alkylbiguaniden mit Benzoin beimpH der Biguanidbasen (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 1063-1073 
    Details
    ISSN: 1434-4475
    Keywords: Benzoin ; reaction with alkylbiguanides ; Imidazoles {piperidine-1-, resp. morpholine-4-[N-(4,5-diphenylimidazol-2-yl)-carboxamidine] ; 1-(4-oxo-5,5-diphenyl-2-imidazolin-2-yl)-3,3-dimethylguanidine} ; Triazines [N-(4-amino-6-phenyl-1,3,5-triazin-2-yl)-benzamide] ; NMR ; X-ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Alkylbiguanides2 a–e react with benzoin (1) at thepH of the base in different ways.1 undergoes in presence of2 a, c oxidation to benzoic acid which reacts with the bases2 a, c to yield 4-phenyl-1,3,5-triazinamines3 c, 4 c; in presence of2 b 1 is transformed to benzil, which reacts with2 b under rearrangement to yield 1-(4-oxo-5,5-diphenyl-2-imidazolin-2-yl)-3,3-dimethylguanidine (5 b). However, the cycloalkylbiguanides2 d, e, react in presence of nitrogen as well as oxygen with1 to yield piperidine-1-[N-(4,5-diphenylimidazol-2-yl)-carboxamidine] (7 d), resp. morpholine-4-[N-(4,5-diphenylimidazol-2-yl)-carboxamidine] (7 e). The structure of7 e was established by means of an X-ray structure analysis. All proton- and carbon resonances were assigned on the basis of 2-dimensional NMR data.
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    New induced cholesteric micellar liquid crystals. Characterization and pitch determination (1989)
    Springer
    Monatshefte für Chemie 120 (1989), S. 393-399 
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    ISSN: 1434-4475
    Keywords: Liquid crystals ; Amphiphile ; Pitch ; D-Glucose ; Polarizing microscope ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurden neue induzierte cholesterische micellare Flüssigkristalle basierend auf Kaliumlaurat und Natriumdecylsulfat hergestellt. Als chirales Molekül zur Ausbildung der Phasen wurde D-Glucose benutzt. Es wurde festgestellt, daß die inverse Ganghöhe proportional zur zugesetzten Gastkomponente ist. Die induzierte Schraubung hängt stark von der Natur des Detergens, der Hauptkomponente der Mesophase, ab. Die Mesophasen werden auf der Basis der mikroskopischen Textur charakterisiert. Die Deuterium-NMR-Spektren in D2O zeigen für diese cholesterischen Mesophasen eine positive diamagnetische Anisotropie.
    Notes: Summary New induced cholesteric micellar liquid crystals have been prepared based on potassium laurate and sodium decyl sulfate. The chiral molecule D-glucose was used as dopant. The inverse pitch length is found to be proportional to the added guest. The twist induced by the dopant strongly depends on the nature of the detergent, the principal component of the mesophases. The mesophases are characterized on the basis of the microscopic textures. Deuterium NMR spectra in D2O shows positive diamagnetic anisotropy for these cholesteric mesophases.
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    1,3-Dipolare Cycloadditionen von 3,4-Dihydro-6,7-dimethoxyisochinolinium-N-methoxycarbonylmethylid mit N-substituierten Maleinimiden (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 529-537 
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    ISSN: 1434-4475
    Keywords: Pyrrolo[2,1-a]isoquinolines ; Azomethine ylides ; NMR ; Stereochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 1,3-Dipolar cycloadditions of 3,4-dihydro-6,7-dimethoxyisoquinolinium-N-methoxycarbonylmethylide2 with N-phenyl- and N-methylmaleimide (3 and4) have been investigated. Cycloadducts of theendo- andexo-type were formed, the structure elucidation and conformational analysis of which has been performed by NMR methods.
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    URL: http://dx.doi.org/10.1007/BF00810862
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    4-Phosphoranylidene-5(4H)-oxazolones — A novel synthesis and properties (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 219-225 
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    ISSN: 1434-4475
    Keywords: 4-Phosphoranylidene-5(4H)-oxazolones ; Phosphorus ylides ; 5(4H)-Oxazolone enolate ion equivalent ; 5-(4H)-Oxazolones ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 4-Phosphoranyliden-5(4H)-oxazolone, eine sehr wenig bekannte Gruppe der Phosphor-ylide, wurden auf einfache Weise nach einem neuen Eintopfverfahren mit guten Ausbeuten hergestellt. Als Ausgangsverbindungen wurden 4-unsubtituierte-5-(4H)-Oxazolone (1) eingesetzt, die unter der Einwirkung von Addukten wie Ph3P-Br2, Bu3P-Br2, Ph3P-CCl4 oder Ph3P-CBr4 in Anwesenheit von Triethylamin in CH2Cl2 bei Zimmertemperatur die Titelverbindungen liefern. Die spektroskopischen Eigenschaften der Ylide werden berichtet und diskutiert.
    Notes: Summary 4-Phosphoranylidene-5(4H)-oxazolones (2), a hardly known class of phosphorus ylides, were readily prepared from 4-unsubstituted-5-(4H)-oxazolones (1) by treatment with Ph3P-Br2, Bu3P-Br2, Ph3P-CCl4, or Ph3P-CBr4 adducts in the presence of triethylamine in CH2Cl2 at room temperature in a novel, efficient one-pot procedure. The spectroscopic properties of the ylides are reported and discussed.
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    Chemie polyfunktioneller Moleküle, 121. Mitt. Cyclopentadienylruthenium(II)-Komplexe desBis(diphenylphosphanyl)amins und -amids sowie des N,N-Bis(diphenylphosphanyl)-methylamins und -ethylamins (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 783-800 
    Details
    ISSN: 1434-4475
    Keywords: Cyclopentadienylruthenium(II) complexes ; Diphosphazane ligands ; Crystal structures ; IR ; Raman ; NMR ; UV/VIS ; Mass spectra ; Hydrogen bridging bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This synthetic and structural work describes a series of half-sandwich cyclopentadienylruthenium(II) complexes containing the diphosphazane ligands [(C6H5)2P]2NR (R=H:Hdppa,1a;R=CH3:dppma,1b;R=C2H5:dppea,1c;R=Li:Lidppa,1d). Treatment of1a, d with CpRuCl(PPh3)2 (Cp=η5-C5H5, Ph=C6H5,2) in a molar ratio of 1:1 in boiling aromatic hydrocarbons affords the neutral complexes CpRuCl(Hdppa) (3) and CpRu(dppa)PPh3 (6). The ionic complexes [CpRu(Ph2P-NR-(PPh2)PPh3)Cl (R=CH3:4a;R=C2H5:4b) are formed by the reaction of1b,c with2. One pot reactions of1a–c with2 in the presence of NH4PF6 in boiling CH3OH give only the ionic compounds [CpRu(Ph2P-NR-PPh2)(PPh3)]PF6 (R=H, CH3, C2H5;5a–c). The sulfur dioxide and hydride complexes [CpRu(Hdppa)η1-SO2]Cl (7) and CpRu(H)Hdppa (8) are obtained by the interaction of3 with SO2 or NaOCH3. All compounds are characterized as far as possible by IR, Raman,31P{1H} NMR,1H NMR,13C{1H} NMR, FD mass spectra, and their conductivity in CH2Cl2 solution. The X-ray crystal structures of3 and5a reveal that the P(1)-N(1)-P(2) angle of the coordinated ligand1a in both complexes is reduced to about 100° in comparison to free uncoordinated1a (119°). This small angle leads to a short P(1)–P(2) bond distance of 259.4 pm in3 and 254.3 pm in5a. The molecules of3 are connected by intermolecular (NH...Cl) hydrogen bridging bonds forming chains along thez axis of the unit cell. The crystals of5a contain two independent pairs of ions in the unit cell (Z=8). In5a no hydrogen bonds exist between the NH-groups and the PF 6 − anions.
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    Chemie polyfunktioneller Moleküle, 126 Mitt. Synthese, Struktur und Tautomerie von 5-Fluor-N(1), N(3)-bis(diphenylphosphanyl)-uracil (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 399-410 
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    ISSN: 1434-4475
    Keywords: Diphenylphosphanyl substituted 5-fluoro-uracils ; X-ray structure determination ; Tautomerism ; NMR ; Vibrational and mass spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 5-Fluoro-uracil (1) reacts with chloro-diphenylphosphane to 5-fluoro-N(1), N(3)-bis(diphenylphosphanyl)uracil (3) which was characterized by X-ray crystallography, IR, and mass spectra.19F,31P{1H},13C{1H}, and1H NMR spectra indicate that3 rearranges inTHF solution to some extent to the tautomeric 5-fluoro-O(2), O(4)-bis(diphenylphosphanyl)uracil (4). If the solvent contains traces of water, Ph2P(O)-PPh2 (6) and uracil derivatives are formed by hydrolysis.
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    Über α,ω-übergangsmetallsubstituierte Oligosilane (1993)
    Springer
    Monatshefte für Chemie 124 (1993), S. 523-528 
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    ISSN: 1434-4475
    Keywords: Cobalt ; Iron ; NMR ; Oligosilanes ; Silanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methyloligosilanes withn=3, 4, 5 and 6 with dicarbonyl-cyclopentadienyl-iron- and tricarbonyl-triphenylphosphane-cobalt-groups in terminal positions were synthesized for the first time and characterized by NMR, IR, and MS. The NMR spectra were discussed in detail.
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    On the tautomerism of hypericin: The 1,6-dioxo tautomer (1993)
    Springer
    Monatshefte für Chemie 124 (1993), S. 923-929 
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    ISSN: 1434-4475
    Keywords: Hypericin ; 7,14-Dioxo-tautomer ; 1,6-Dioxo-tautomer ; NMR ; UV-Vis ; Fluorescence ; Force field calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Das 1,6-Dioxo-Tautomere des Hypericins wurde durch basen- und BF3-katalysierte Tautomerisierung des natürlichen, stabilen 7,14-Dioxo-Tautomers erhalten. Dessen Isolierung wurde durch die Schwerlöslichkeit in Methanol ermöglicht. Es wurde durch spektroskopische Methoden identifiziert und charakterisiert, und seine detaillierte Struktur wurde aus Kraftfeld-Rechnungen abgeleitet.
    Notes: Summary The 1,6-dioxo-tautomer of hypericin was obtained by basic and BF3 catalyzed tautomerization of the natural and most stable 7,14-dioxo-tautomer. The isolation of this tautomer was aided by its insolubility in methanol. It was identified and characterized by spectroscopic methods, and its detailed structure was derived by means of force field calculations.
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    Formation of 3,4-diazabicyclo[4,3,0]non-2-ene and N,N′-azo-3-azabicyclo[3,3,0]octane by oxidation of an alicyclic hydrazine. influence ofpH on the diazene rearrangement (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 1113-1120 
    Details
    ISSN: 1434-4475
    Keywords: Synthesis ; 3,4-Diazabicyclo[4,3,0]non-2-ene ; N,N′-Azo-3-azabicyclo[3,3,0]octane ; Diazene ; Hydrazine ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 3,4-Diazabicyclo[4,3,0]-non-2-en und N,N′-Azo-3-azabicyclo[3,3,0]oktan sind die Hauptreaktionsprodukte der Oxidation von N-Amino-3-azabicyclo[3,3,0]oktan durch Chloramin. Die Interaktion führt übergangsweise zur Bildung eines gesättigten bizyklischen Aminonitrens (Diazens). Oberhalb despH-Wertes 13 lagert sich das Diazen intramolekular um und bildet ein Hydrazon. Unterhalb despH-Wertes 9 fällt ein weißer Niederschlag aus (Tetrazen), der von einer Dimerisierung zwischen for molekularen und protonierten Form von Aminonitren herrühren dürfte. Für die dazwischenliegenden Werte (9 〈pH 〈 13) erhält man eine Mischung aus beiden Verbindungen. Sie wurden isoliert und mit Hilfe von UV, GC/MS, IR, und1H/13C-NMR untersucht. Ein Reaktionsmechanismus wird vorgeschlagen.
    Notes: Summary 3,4-Diazabicyclo[4,3,0]non-2-ene and N,N′-azo-3-azabicyclo[3,3,0]octane are the main products of the oxidation of N-amino-3-azabicyclo[3,3,0]octane by chloramine. The reaction leads to the transient formation of a saturated bicyclic aminonitrene (diazene). AtpH 〉 13, the diazene undergoes an intramolecular rearrangement to afford a hydrazone. AtpH 〈 9, a white solid is formed resulting from the dimerization of the molecular and protonated forms of the aminonitrene. At intermediatepH-values, a mixture of both species is obtained. They have been isolated and characterized by UV, GC/MS, IR, and1H/13CNMR. A reaction mechanism is proposed.
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    Zur Adsorption von Olefinmolekülen in Zeolithen (1988)
    Springer
    Monatshefte für Chemie 119 (1988), S. 913-919 
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    ISSN: 1434-4475
    Keywords: Zeolites ; Olefine molecules ; NMR ; Chemical shift ; Quantum chemical calculations ; CNDO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The interaction between 1-olefine molecules and Na+ ions in zeolites of type NaY were studied by13C NMR spectroscopy and quantum chemical calculations. Characteristic chemical shifts of olefinic carbon atoms indicate a terminal arrangement of the cation near the olefinic part of the molecule.
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    Isolation and structure determination of two new macrocyclic biaryl ethers fromGaruga gamblei (1988)
    Springer
    Monatshefte für Chemie 119 (1988), S. 1047-1050 
    Details
    ISSN: 1434-4475
    Keywords: Garuga gamblei ; Burseraceae ; Garugamblin ; Macrocyclic biaryl ether ; Structure determination ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Aus der Rinde vonGaruga gamblei King (Burseraceae) wurden zwei neue makrocyclische Biarylether isoliert. Die Struktur der Verbindungen wurde mittels NMR-Spektroskopie bestimmt.
    Notes: Abstract Two new macrocyclic biaryl ethers have been isolated from the bark ofGaruga gamblei King (Burseraceae). The structure of the compounds has been established by NMR spectroscopy.
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    Radical reactions of N-heterocyclic compounds, XV. Radial intermediates and end products of the oxidation of 3-anilino-1,5-diphenylpyrazoles with Pb(OAc)4 (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 261-270 
    Details
    ISSN: 1434-4475
    Keywords: Aminyl radicals ; ESR ; NMR ; Pyrazoles ; Triarylaminium cation radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die substituierten 3-Anilino-1,5-diphenylpyrazole1a–i wurden mit Pb(OAc)4 in Benzol oder CH2Cl2 oxidiert. Die intermediären Aminylradikale3f–i wurden ESR-spektroskopisch bei der Oxidation der im Anilinrest methylsubstituierten Pyrazole1f–i nachgewiesen. Die ESR-spektroskopisch nach Oxidation der Pyrazole1a–e beobachteten Radikalintermediate interpretieren wir als Kationradikale6a–e. Diese werden durch Weiteroxidation der Dimeren4a–e gebildet, deren Struktur durch NMR-Untersuchungen und15N-Markierung bewiesen wurde.
    Notes: Summary Substituted 3-anilino-1,5-diphenylpyrazoles1a–i were oxidized with Pb(OAc)4 in benzene or CH2Cl2 solution. The ESR measurements confirmed the formation of aminyl radicals3f–i frompara-CH3 substituted pyrazoles1f–i. The radical intermediates from unsubstituted pyrazoles1a–e were assigned to triarylaminium cation radicals These were generated by consecutive oxidation of the dimeric products4a–e whose structure was proven by NMR spectroscopy and15N labeling.
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    The steric structure of multiflorine methylation products (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 233-239 
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    ISSN: 1434-4475
    Keywords: Enaminoketones ; Lupin alkaloid ; Multiflorine ; NMR ; Nucleophilic methylation ; Stereospecificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Multiflorin (1), ein Lupin-Nebenalkaloid, ergibt bei Umsetzung mit Methyllithium oder Methylmagnesiumiodid 4S-4-Hydroxy-4-methyl-2,3-didehydrospartein (2) und 2S-2-Methyl-4-oxospartein (3) als Hauptprodukte. Ihre NMR-spektroskopisch (1H und13C) aufgeklärte räumliche Struktur weist auf eine Stereoselektivität der erwähnten Reaktionen hin. Die beobachteten nucleophilen 1,2- und 1,4-Additionen zeigen, daß sich die Regiospezifität der Einwirkung von MeLi oder MeMgl auf Multiflorin von jener bis jetzt bekannter Alkylierungen von Enaminoketonen unterscheidet.
    Notes: Summary Multiflorine (1) — a minor lupine alkaloid — treated by methyl lithium or methyl magnesium iodide affords 4S-4-hydroxy-4-methyl-2,3-didehydrosparteine (2) and 2S-2-methyl-4-oxosparteine (3), respectively, as the dominating products. Their steric structure, determined by1H and13C NMR techniques, points to stereospecific preferences of these reactions. The observed nucleophilic 1,2- and 1,4-additions indicate that regiospecificity of the action of MeLi or MeMgI on multiflorine is different from that of the so far known similar alkylation of other enamino ketones.
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    Synthesis and stereochemistry of 8-methyl-5-nitro-1-octalones (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 1011-1019 
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    ISSN: 1434-4475
    Keywords: Precursors of strigol analogues ; Michael reaction ; NMR ; Molecular modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung BasenkatalysierteMichael-Addition von 5-Nitropentan-2-on-ethylenketal (1) und Cyclohex-2-enon (2), anschließende Entfernung der Schutzgruppe und darauffolgende Aldolkondensation liefert isomer 8-Methyl-5-nitro-1-octalone (5a,b). Struktur, relative Konfiguration und Konformation von5a und5b wurden mittels1H- und13C-NMR-Spektroskopie aufgeklärt.
    Notes: Summary Base catalyzedMichael addition of 5-nitropentan-2-one ethylene ketal (1) and cyclohex-2-enone (2), subsequent deprotection, and intramolecular aldol condensation yields the 8-methyl-5-nitro-1-octalone isomers (5a,b). The structure, relative configuration, and conformation of5a and5b were elucidated utilizing the results of1H and13C NMR investigations
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    Conformational analysis of thia crown ether derivatives by NMR spectroscopy and molecular mechanics calculations (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 1145-1152 
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    ISSN: 1434-4475
    Keywords: NMR ; Thia crown ethers ; Conformation ; Molecular mechanics calculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Aus Tetrachlorbrenzcatechin-bisallylether (1) und Schwefeldichlorid wurden neben der 1,10-Dithia-dibenzo-18-krone-64 die 9- und 10-Ring-Derivate2 und3 erhalten. In der 10-Ring-Verbindung wurde erstmaligMarkovnikov- undanti-Markovnikov-Konstitution der β-Chlor-thio-Gruppierung in einem Thiamakrocyclus nebeneinander vorgefunden. Das isolierte Diastereomere von3 zeigt bei Temperaturen unter −50 °C zwei Konformere. Die Signalzuordnung war mit homo-und heteronuklearen COSY- sowie mit phasensensitiven NOESY-Spektren möglich. Mit Hilfe molekülmechanischer Rechnungen konnten aus den13C-NMR-Verschiebungen und den vicinalen H,H-Kopplungskonstanten die Vorzugskonformeren und die relative Konfiguration bestimmt werden.
    Notes: Summary Addition of sulfur dichloride to tetrachlorocatechol-bisallylether (1) yields the 9- and 10-ring thia crown ether derivatives2 and3, respectively, together with the dithia-18-crown-6-ether4. The 10-membered ring compound3 represents the first thia macrocycle containing bothMarkovnikov andanti-Markovnikov constitution of the β-chloro-thio structural segments in the same molecule. By1H and13C NMR spectroscopy, equal amounts of two preferred conformers of the only isolated diastereomer of3 were observed at temperatures below −50°C. The signals were assigned to these conformers using COSY, HETCOR, and phase sensitive NOESY spectra at low temperatures. The preferred conformations and the relative configuration were determined using the different effects of γ gauche -and γ anti -positions in13C NMR chemical shifts and analyzing vicinal3 J H,H coupling constants. These results were confirmed by molecular mechanics calculations.
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    Molecular Modeling Study of the PtCl2 Complexes of Unsaturated S2On+1-Coronands: Dynamic Simulations and Investigation of the Ring Interconversion (1999)
    Springer
    Journal of molecular modeling 5 (1999), S. 72-77 
    Details
    ISSN: 0948-5023
    Keywords: Keywords Thiacrown ether ; NMR ; Pt(II) complexes ; Molecular dynamic simulations ; Ring interconversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract   Maleonitrile-dithiacrown ethers mn-12S2O2 - mn-21S2O5 (mn = maleonitrile) are preorganized S2On+1-coronands (n = 1–4) which force B, AB and A class metal ions into mixed S/O coordination spheres. Moreover, they form chelate complexes with MX2 salts (M = Pd, Pt; X = Cl, Br), which were studied in this paper. The structures of mn-S2On+1 and [PtCl2(mn-S2On+1)] (n = 2, 3) were investigated theoretically by empirical and semiempirical methods using SYBYL (TRIPOS force field) and MSI/DISCOVER97 (ESFF force field). mn-12S2O2 was investigated experimentally by X-ray analysis and 1D and 2D NMR spectroscopy in solution and the complex formation was studied by 1H, 13C and 195Pt NMR titration experiments, respectively. S-inversion was also investigated in order to determine the ring corresponding interconversional barriers. Different orientations of the macrocyclic ring system mn-18S2O4 and of its transition states are shown.
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    URL: http://dx.doi.org/10.1007/s008940050106
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    Knowledge-based Homology Modeling and Experimental Determination of Amino Acid Side Chain Accessibility by the Laser Photo CIDNP (Chemically Induced Dynamic Nuclear Polarization) Approach in Solution: Lessons from the Small Sialidase of Clostridium perfringens (1996)
    Springer
    Journal of molecular modeling 2 (1996), S. 446-455 
    Details
    ISSN: 0948-5023
    Keywords: Sialidase ; NMR ; Protein modelling ; Molecular dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The success of knowledge-based homology modelling is critically dependent on the predictive potency of the program structure-based calculations, which attempt to translate homologous sequences into three-dimensional structures, and on the actual relevance of the crystal structure for the protein topology. As quality control, experimental data for selected parameters of the protein′s conformation are required. Using the crystal structure of the sialidase of Salmonella typhimurium as framework for model building of the homologous enzyme from Clostridium perfringens, a set of energy-minimised conformers is derived. These proteins present e.g. Tyr, Trp and His residues with an assessable area on the surface, since the side chains of these amino acid residues are responsive to chemically induced dynamic nuclear polarization (CIDNP), monitored by NMR. Hence, as first lesson, a comparative analysis for model-derived and experimentally determined values can be performed. The second lesson of this study concerns the notable impact of single amino acid substitutions (Tyr/Phe, Cys/Ser) on the surface accessibility of the CIDNP-reactive amino acid side chains in mutant forms of the sialidase. Corroborating the predictions from the theoretical calculations, the spectra of the engineered mutants reveal marked and non-uniform alterations. Thus, the effect of apparently rather conservative amino acid substitutions on a distinct conformational aspect of this protein, even at distant sites, should not be underestimated.
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    URL: http://dx.doi.org/10.1007/s0089460020446
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    Spectroscopic studies of cobalt-substituted ferredoxin fromClostridium pasteurianum (1989)
    Springer
    BioMetals 2 (1989), S. 135-141 
    Details
    ISSN: 1572-8773
    Keywords: Ferredoxin ; Clostridium pasteurianum ; Cobalt derivative ; ERP ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Ferredoxin fromClostridium pasteurianum substituted with two Co atoms did not give any cobalt EPR signal at 8 K as isolated, but upon reduction with sodium dithionite, a broad signal appeared withg values that indicate highspin (S=3/2) Co(II). These signals were distinct from Co(II)-dithiothreitol signals, and disappeared upon reoxidation with air. Under anaerobic incubation of apoferredoxin with Co(II), a green derivative showed a visible spectrum typical of tetrahedral Co(Il)-thiolate coordination, which shifted dramatically upon exposure to air. The1H-NMR spectrum of the aerobically isolated protein is reported at 300 MHz; magnetic susceptibility measurements were indicative of a diamagnetic species. These spectroscopic studies indicate that Co(II)-substituted ferredoxin is oxidized to low-spin Co(III)-ferredoxin in the presence of sulfide and oxygen. The diamagnetic Co(III) state could reversibly be reduced to highspin Co(II) by sodium dithionite.
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    URL: http://dx.doi.org/10.1007/BF01142551
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    Bacterial siderophores : structure and NMR assignment of pyoverdins Pa, siderophores ofPseudomonas aeruginosa ATCC 15692 (1990)
    Springer
    BioMetals 3 (1990), S. 155-170 
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    ISSN: 1572-8773
    Keywords: Siderophores ; Pyoverdins ; Pseudomonas aeruginosa ; FAB-MS ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In iron-deficient conditions,Pseudomonas aeruginosa ATCC 15692 synthesizes two major siderophores, pyoverdins Pa and pyoverdin Pa B. Two other compounds, pyoverdin Pa A (occurring from hydrolysis of pyoverdin Pa during the culture) and pyoverdin Pa C (occurring artifactually during the purification procedure) were also isolated. All these compounds possess the same partly cyclic peptide chain wherel-Orn(δOH · HCO) isN δ-formyl,N δ-hydroxy-l-ornithine. The chain is bound to a chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline and having the (S) configuration. The four pyoverdins differ only in the acyl substituent bound to the nitrogen atom bound to carbon C3 of the chromophore. This is succinamide (pyoverdin Pa), succinic acid (pyoverdin Pa A), methyl succinate (pyoverdin Pa C) and 2-oxoglutaric acid (pyoverdin Pa B). The complete1H- and13CNMR assignments, using two-dimensional total correlation NMR spectroscopy (TOCSY) and rotating-frame Overhauser enhancement spectroscopy (ROESY) procedures, as well as1H-13C correlations, are reported. The complete sequence of the peptide using CHα-NH correlations was achieved by NMR and confirmed the partly cyclic structure earlier reported using fast-atom-bombardment mass spectrometry (FAB-MS) on the siderophores and their dansylated fragments [Briskot G, Taraz K, Budzikiewicz H (1989)Liebigs Ann Chem: 375–384]. The use of these NMR procedures appears to be a tool of choice and a complementary approach to FAB-MS in the structure determination of some complex pyoverdins.
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    In situ13CNMR study of “conjunct polymerisation” of 1-pentene in 95% sulfuric acid (1996)
    Springer
    Catalysis letters 38 (1996), S. 115-121 
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    ISSN: 1572-879X
    Keywords: NMR ; acid catalysis ; pentene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 13C NMR study of “conjunct polymerisation” of 1-pentene in 95% sulfuric acid demonstrated that this is a carbenium ion reaction, where the esters are the precursors of carbenium ions. In the first step of the reaction a complicated mixture of primary and secondary mono- and dipentyl esters is formed. In an excess of the acid the esters are decomposed yielding aliphatic carbenium ions, which are then involved in secondary reactions resulting in the final products. Similar to heterogeneous catalysis on zeolites, the steady state concentration of the aliphatic carbenium ions during the reaction is, however, too low for their direct detection by NMR.
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    129Xe-NMR study of coke distribution in dealuminated HY zeolites (1990)
    Springer
    Catalysis letters 5 (1990), S. 143-154 
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    ISSN: 1572-879X
    Keywords: NMR ; xenon ; coke ; zeolite ; extra-framework aluminium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolites coking has been studied by129Xe-NMR technique. The distribution of the coke is heterogeneous on the supercage surface at low cokage level. When coking increases up to 10% the supercages are lined with coke and the residual internal volume consists of narrow channels. Beyond 10% the coke also affects the external surface of the zeolites, with the formation of coke microcavities between the crystallites. This technique has also enabled us to show the role of extra-framework Al in the cracking activity of zeolites.
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    URL: http://dx.doi.org/10.1007/BF00763946
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    In situ MAS NMR investigations of molecular sieves and zeolite-catalyzed reactions (1999)
    Springer
    Catalysis letters 58 (1999), S. 1-19 
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    ISSN: 1572-879X
    Keywords: zeolites ; chemicals ; NMR ; alkane activation ; reaction mechanism ; in situ investigation ; alkylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid-state MAS NMR is a powerful technique to study heterogeneous catalysts and the way by which they operate. In situ MAS NMR has been demonstrated to be a powerful method to understand reaction mechanisms, to study the nature, dynamics and reactivity of surface intermediates and active sites, and to characterize structural modifications in the catalyst itself, in particular when using 13C strategically labelled substrates. In this paper, three examples selected from our own work are used to illustrate the potential of in situ MAS NMR. They are the formation of cumene and its isomerization to n-propylbenzene on zeolite H-ZSM-11, the activation of propane at low temperature and the alkylation of benzene with propane on zeolite H-ZSM-5, and the characterization of the aluminophosphate molecular sieve VPI-5 structure with temperature. Studies of the alkylation of benzene with propene confirmed that cumene was the primary reaction product. The undesired n-propylbenzene by-product results from the intermolecular reaction between cumene and benzene, enhanced by molecular shape-selective effects in medium pore size zeolites (e.g., H-ZSM-11). It explains why large pore zeolites, e.g., zeolite Beta, are used commercially today for this process. Propane can be activated at low temperature (ca. 573 K) on bifunctional medium pore size zeolites possessing intimately related acidic Brønsted sites and a dehydrogenation function provided by Ga or Zn species. In Ga/H-ZSM-5 catalysts, at 573 K, the activation of propane was shown to occur via a protonated pseudocyclopropane (PPCP) intermediate (or transition state). The latter evolves in a manner that can be formally described by the formation of CH 3 + , C2H 2 + , and C3H 7 + carbenium ion intermediates. These species can react with olefins, alkanes, or other electron-rich molecules such as benzene. The primary reaction products of the reaction of propane with benzene are n-propylbenzene (in small amount), ethylbenzene and toluene. Their subsequent reactions lead eventually to toluene and xylenes as the final products. In the structural characterization of VPI-5, 27Al, 31P, and 27Al nutation MAS NMR spectra show that, at 294 K, fully hydrated VPI-5 contains three equally populated Al and P crystallographic sites and that one-third of Al is 6-coordinate. The VPI-5 structure then belongs to the P63 space group. Above 353 K, VPI-5, fully or partially hydrated, undergoes a structural transformation to a higher framework symmetry, i.e., the P63cm space group. The transformation occurs at nearly the same temperature in both cases, indicating that the breakdown of the hydrogen-bonded helical water structure inside the VPI-5 pores is not a factor in the process.
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    Metal ion binding to calmodulin: NMR and fluorescence studies (1998)
    Springer
    BioMetals 11 (1998), S. 213-222 
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    ISSN: 1572-8773
    Keywords: calmodulin ; fluorescence spectroscopy ; metal ions ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Calmodulin is an important second messenger protein which is involved in a large variety of cellular path-ways.Calmodulin is sensitive to fluctuations in the intracellular Ca levels and is activated by the bindingof four Ca ions. In spite of the important role it plays in signal transduction pathways, it shows a surpris-inglybroad specificity for binding metal ions. Using 15N-Gly biosynthetically-labelled calmodulin, we havestudied the binding of different metal ions to calmodulin, including K+, Na+, Ca, Mg, Zn, Cd, Pb, Hg, Sr, La and Lu, by 1H, 15N HMQC NMR experiments. The effects of these ions on the substrate-bindingability of calmodulin have also been studied by fluorescence spectroscopy of the single tryptophan residue in a 22-residue synthetic peptide encompassing the skeletal muscle myosin light chain kinase calmod-ulin-binding domain. Most of these metal ions can activate a calmodulin target enzyme to some extent,though they bind to calmodulin in a different manner. Mg, which is of direct physiological interest, has adistinct site-preference for calmodulin, as it shows the highest affinity for site I in the N-terminal domain,while the C-terminal sites III and IV are the high affinity binding sites for Ca (as well as for Cd ). At ahigh concentration of Mg and a low concentration of Ca, calmodulin can bind Mg in its N-terminallobe while the C-terminal domain is occupied by Ca; this species could exist in resting cells in which the Mg level significantly exceeds that of Ca. Moreover, our data suggest that the toxicity of Pb-which,like Sr, binds with an equal and high affinity to all four sites-may be related to its capacity to tightlybind and improperly activate calmodulin.
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    Synthesis of aluminum rich MCM-41 (1995)
    Springer
    Catalysis letters 31 (1995), S. 267-272 
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    ISSN: 1572-879X
    Keywords: MCM-41 synthesis ; NMR ; FTIR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis of MCM-41 mesoporous compounds with Si/Al ratios as low as 2 without observing the presence of octahedral Al in27AlMAS NMR is reported. FTIR spectra of chemisorbed pyridine indicated that MCM-41 materials in their protonated form exhibit both Brønsted and Lewis acid sites.
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    Synthesis and characterization of highly ordered MCM-41 in an alkali-free system and its catalytic activity (1996)
    Springer
    Catalysis letters 38 (1996), S. 33-37 
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    ISSN: 1572-879X
    Keywords: MCM-41 synthesis ; alkali-free gel ; n-heptane cracking ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract MCM-41 mesoporous molecular sieve materials are synthesised using aqueous ammonia solution to adjust the pH of the reactant gel. Highly ordered MCM-41 with Si/Al ratio as low as 14 was obtained and characterised by27A1 MAS NMR, XRD, N2-adsorption, benzene sorption, and NH3-TPD measurements. The acidity of MCM-41 materials obtained in this system was conveniently generated through straightforward calcination of the as-synthesised sample. More mild acidic sites generated could be due to the avoidance of the multiple calcination procedure and/or the trace sodium species which are the poisons to Brønsted acid. The catalytic activities forn-heptane cracking and isomerization ofm-xylene were investigated, and these were in accordance with the known properties of MCM-41.
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    Stabilization of CuZSM-5 NOx reduction catalysts with lanthanum (1996)
    Springer
    Catalysis letters 41 (1996), S. 47-53 
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    ISSN: 1572-879X
    Keywords: CuZSM-5 ; lanthanum ; DeNOx ; XRD ; NMR ; XPS ; ISS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of high temperature steam treatment on the activity and selectiv ity of CuZSM-5 catalysts for the selective catalytic reduction of NO with propene have been examined. Loss of activity and selectivity on steam treatment is due to framework dealumination of the zeolite, which causes migration of Cu out of the zeolite pores to the external surface. Pre-exchange of the zeolite with La3+ cations inhibits the dealumination, preventing migration of Cu to the surface and allowing the catalyst to retain high activity and N2 selectivity after steam treatment. The deactivation of the catalysts was monitored using X-ray powder diffraction, magic angle spinning27Al and29Si nuclear magnetic resonance, X-ray photoelectron spectroscopy and ion scattering spectroscopy.
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    An NMR study of acid sites on chlorided alumina catalysts using trimethylphosphine as a probe (1994)
    Springer
    Catalysis letters 26 (1994), S. 235-246 
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    ISSN: 1572-879X
    Keywords: NMR ; TMP ; acid sites ; gamma alumina ; chlorine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The MAS-NMR spectra of adsorbed trimethylphosphine (TMP) were used to determine the concentration of Brønsted and Lewis acid sites on pure and chlorinatedγ-Al2O3 samples. Chlorination with CHCl3,CCl4 or AlCl3 promoted the formation of Brønsted acid centers, which are characterized by the protonated adduct of TMP. This adduct has a31P chemical shift of ca. −3.8 ppm and a JP−H scalar coupling of 517 Hz. Additional resonances in the −44 to −54 ppm range are attributed to Lewis acid-base pairs. In some cases a partially resolved JP−Al coupling is observed, which confirms the assignment. Upon thermal treatment of a chlorinated sample at temperatures 〉 200°C, the concentration of Brønsted acid centers decreased; the concentration of one type of Lewis acid increased and another remained almost constant. In a parallel set of experiments the initial conversion ofn-hexane at 150°C and the yields of cracking and isomerization products were determined. Comparable functional relationships were observed between the loss of Brønsted acid sites and the decrease in yields of both cracking and isomerization products. These results suggest that Bransted acidity is responsible for the cracking and isomerization ofn-hexane over chlorided aluminas at 150°C.
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    An NMR study of acid sites on sulfated-zirconia catalysts using trimethylphosphine as a probe (1994)
    Springer
    Catalysis letters 27 (1994), S. 305-314 
    Details
    ISSN: 1572-879X
    Keywords: sulfated zirconia ; NMR ; acidity ; trimethylphospine ; isobutane alkylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Concentrations of Brønsted and Lewis acid sites on sulfated-zirconia catalysts were determined using the31P MAS NMR spectra of adsorbed trimethylphospine. A sample that had been calcined and exposed to air for a long period exhibited only Brønsted acidity; however, treatment of the sample at progressively higher temperatures resulted in the development of at least three types of Lewis acidity, along with a decrease in the concentration of Brønsted acid sites. In a related study the activity of these catalysts for the alkylation of isobutane with 2-butene was determined. The aged catalyst was inactive, but activation of the material at 100°C resulted in the most active catalyst. Thermal treatment at higher temperatures resulted in a loss in activity which paralleled the decrease in the Brønsted acid sites. These results are consistent with a model in which strong Brønsted acidity is a result of the interaction between bisulfate groups and adjacent Lewis acid sites.
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    Room-temperature formation of thermally stable aluminium-rich mesoporous MCM-41 (1998)
    Springer
    Catalysis letters 52 (1998), S. 21-23 
    Details
    ISSN: 1572-879X
    Keywords: RT synthesis ; thermal analysis ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The room-temperature (RT) synthesis of MCM-41 mesoporous compounds with high substitution levels of aluminium (Si / Al = 1.5) is achieved in a minimum time of synthesis. The compound shows similar characteristics to hydrothermally synthesized materials. 27Al NMR study confirms the presence of tetrahedral aluminium in as-synthesized material as well as in the calcined material without observing the presence of octahedral aluminium after calcination.
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    What do we know about the acidity of solid acids? (1999)
    Springer
    Catalysis letters 62 (1999), S. 1-13 
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    ISSN: 1572-879X
    Keywords: acid catalysis ; zeolites ; temperature‐programmed desorption ; microcalorimetry ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract With a proper understanding of the nature of solid acidity, zeolites and other solid acids have great potential for replacing homogeneous acids in a wide range of catalytic applications. This paper describes results from our laboratory on the characterization and description of the acid sites in high‐silica zeolites, especially H‐MFI. A crucial observation from this work is the identification of stoichiometric adsorption complexes, one molecule per framework Al, for a wide range of adsorbates, including amines, alcohols, nitriles, ketones, and thiols. Examples are given in which temperature‐programmed desorption is used to identify these complexes and characterize their initial chemistries. Calorimetric measurements on the 1:1 complexes have been used to compare the enthalpies of protonation in the zeolite to enthalpies of protonation in the gas phase and in aqueous phase and to demonstrate that a gas‐phase basis provides better predictive capabilities. The issue of carbenium‐ion stabilities is discussed, as well as the unusual catalytic properties of acid sites formed by framework substitution of Fe. The effect of sorption and cavity size on reactions is described. Finally, the problems associated with trying to define or characterize solid acids by using ammonia TPD or 13C NMR isotropic shifts of ketones without proper consideration of the complicated nature of these techniques are discussed.
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    Atoms to astronomy: Computer graphics at the Jet Propulsion Laboratory (1986)
    Springer
    The visual computer 2 (1986), S. 159-163 
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    ISSN: 1432-2315
    Keywords: Education ; Animation ; Computer graphics ; Physics ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Within the Jet Propulsion Laboratory in Pasadena, California, state of the art computer graphics animation is done in the Computer Graphics Laboratory. The topics of the animations cover many scientific disciplines. Specific features of the system developed there, both hardware and software, are discussed. The prime mover of the effort is Dr. James F. Blinn of Pasadena; his role and experiences are elaborated. Their current largest project is The Mechanical Universe; the system is used for its production.
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    Use of a symbolic algebra program in NMR (1986)
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    Microchimica acta 89 (1986), S. 303-312 
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    ISSN: 1436-5073
    Keywords: NMR ; symbolic algebra ; computer algebra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Computer algebra (CA) on microcomputers may be used as a convenient tool to gain greater insight into the use and design of modern NMR pulse sequences and into their relation to the spin parameters. Some applications are demonstrated.
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    The ORD, CD and UV spectra of sulphides derived from carvone (1983)
    Springer
    Monatshefte für Chemie 114 (1983), S. 195-209 
    Details
    ISSN: 1434-4475
    Keywords: Carvone sulphides ; CD ; NMR ; ORD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die CD- und ORD-Spektren aromatischer und aliphatischer Sulfide von Carvon werden mit Spektren von Dicarvonsulfid und verwandten Verbindungen verglichen. Die Spektren werden in bezug auf Molekülstrukturen, die durch NMR-Spektren bewiesen wurden, diskutiert und mit den betreffenden Elektronenübergängen in Wechselbeziehung gebracht.
    Notes: Abstract The ord and cd spectra of aromatic and aliphatic sulphides derived from carvone are compared with the spectra of dicarvone sulphide and related compounds. The spectra are discussed in relation to the structure of the molecules, as evidenced by the nmr spectrum, and correlated with the electronic transitions involved.
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    Mixed dialkyltin(IV) trifluoroacetates (1983)
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    Monatshefte für Chemie 114 (1983), S. 661-667 
    Details
    ISSN: 1434-4475
    Keywords: IR ; Mass spectra ; Mössbauer spectra ; NMR ; 19 F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die gemischten Dialkylzinn(IV)-trifluoroacetateMe EtSn(O2CCF3)2,Et Pr n Sn(O2CCF3)2 undPr n Bu n Sn(O2CCF3)2 wurden über Metathese-Reaktionen der entsprechenden Dialkylzinn(IV)-chloride mit Silbertrifluoracetat in CH2Cl2 dargestellt. Sie sind monomer in Benzol und nichtleitend inMeNO2 undMeCN. Die IR-Spektren zeigen zweizähnige Trifluoracetat-Gruppen an. DieMössbauer-Spektren bestätigen dietrans-Anordnung derR-Sn-R′-Einheit. Die1H-,19F-NMR und die Massenspektren werden ebenfalls diskutiert.
    Notes: Abstract Mixed dialkytin(IV) trifluoroacetates,Me EtSn(O2CCF3)2,Et Pr n Sn(O2CCF3)2 andPr n Bu n Sn(O2CCF3)2 have been prepared by metathetical reactions of the corresponding dialkyltin(IV) chlorides with silver trifluoroacetate in CH2Cl2. They are monomeric in benzene and nonconducting inMeNO2 andMeCN. Bidentate trifluoroacetate groups are indicated by their IR spectra.Mössbauer spectra confirmtrans-arrangement of theR-Sn-R′ moiety.1H,19F NMR and mass spectra are also discussed.
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    A comprehensive study of isoskeletal analogs of dibenzo[a,c]anthracene (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 13-30 
    Details
    ISSN: 1434-4475
    Keywords: Dibenzo[a,c]anthracene ; Dibenzo[a,c]phenazine ; Aza arenes ; Dibenzo[a,c]acridine ; Ionization energies ; Cyclopentadienone ; MO Calculations ; NMR ; Mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Im Zuge eines Überblicks über die Chemie von Cyclopentadienon-Derivaten und Aza-Analogen von Dibenzo[a,c]anthracen werden zusätzliche Erkenntnisse aus Molekülorbitalrechnungen (MO) und spektroskopischen Untersuchungen präsentiert. Es wird die Tendenz der MO's zur Koplanarität von Phenylsubstituenten an Benzenoiden gezeigt. Aus sterischen Gründen rechtwinkelig orientierte Phenylsubstituenten ergeben in den NMR-Spektren starke Abschirmeffekte für die entsprechend liegenden Protonen. Aus den rechnerischen und experimentellen Ergebnissen wird eine relative Ordnung der Aza-Arenanalogen bezüglich ihrer chemischen Eigenschaften abgeleitet. Da bis jetzt nur ca. 1.87% der möglichen isoskelettalen Analogen von Dibenzo[a,c]anthracen in der Literatur beschrieben sind, sollten die präsentierten Richtlinien dazu geeignet sein, die wesentlichsten chemischen Eigenschaften der noch nicht synthetisierten Analogen vorauszusagen.
    Notes: Abstract While reviewing the chemistry of cyclopentadienone derivatives and aza isoskeletal analogs of dibenzo[a,c]anthracene, additional molecular orbital (MO) and spectroscopic results and insights are presented. The MO tendency for coplanarity of phenyl substituents on benzenoids is demonstrated. Perpendicularly oriented phenyl substituents resulting from steric interactions strongly shield appropriately situated protons in NMR spectra. The principles of alternating polarity and parallel correspondence in conjunction with MO methods are used to relatively order aza arene isoskeletal analogs according to their chemical properties. Since less than 1.87% of the isoskeletal analogs of benzo[a,c]-anthracene have been reported, this summary work will help one to forecast the major chemical properties of those not yet synthesized.
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    Cycloaddition reactions of 5-deutero-1-phenyl-4-vinylpyrazole. Stereoselectivecis “ene” reaction and simplification of NMR spectra of mixtures of cycloadducts (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 81-84 
    Details
    ISSN: 1434-4475
    Keywords: Cycloaddition ; Ene-reaction ; Vinylpyrazole ; NMR ; Deuteration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Reaktion von Methylpropiolat (MP) mit an der 5-Stellung deuteriertem 1-Phenyl-4-vinylpyrazol wurde zur vereinfachten Interpretation der1H-NMR-Spektren einer 1:2 Mischung von Addukten aus der Diels-Alder-Cycloaddition mit nachfolgender nicht-regioselektiver „en-Reaktion“ eingesetzt. Das deuterierte Substrat erlaubte zugleich auch die Bestimmung der Stereochemie der en-Reaktion als einen konzertiertencis-Prozeß.
    Notes: Summary The reaction of methyl propiolate (MP) with 1-phenyl-4-vinylpyrazole deuterated in the five position has clarified the1H NMR spectrum of the mixture of the adducts 1:2 which are obtained as a result of a Diels-Alder cycloaddition followed by a non-regioselective “ene” reaction. The deuterated substrate allowed at the same time to establish the stereochemistry of the ene reaction as a concertedcis process.
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    URL: http://dx.doi.org/10.1007/BF00810298
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    1H,13C and19FNMR studies on the structure of the intramolecularly hydrogen bondedcis-enols of 2-trifluoroacetylcycloalkanones (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 157-163 
    Details
    ISSN: 1434-4475
    Keywords: Fluorinated β-diketones ; NMR ; Enol forms ; Intramolecular hydrogen bond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die1H-,13C- und19F-NMR-Spektren einiger 2-Trifluoracetylcycloalkanone mit fünf-, sechs-, sieben- und achtgliedrigen Ringsystemen wurden untersucht. Mittels19F-NMR konnte über 90% Enolisierung nachgewiesen werden. Der Effekt der Ringgröße auf die chemischen Verschiebungen in den1H-,13C- und19F-NMR-Spektren und auf die13C-19F-Kopplungskonstanten werden diskutiert. Die Enolisierungsrichtung dieser Systeme wurde unter Einsatz der NMR-Spektren untersucht: dabei ergab sich eine dominierende exocyclische Enolform für die Fünfringe und eine endocyclische Enolform für die sechs-, sieben- und achtgliedrigen Ringe.
    Notes: Summary The1H,13C and19F NMR spectra of some 2-trifluoroacetylcycloalkanones comprising five-, six-, seven-, and eight-membered ring systems have been studied. These systems have been shown by19F NMR spectroscopy to be over 90% enolized. The effects of ring size on the1H,13C and19F chemical shifts and13C-19F coupling constants are discussed. The direction of enolization in these systems was investigated by1H,13C and19F NMR spectroscopy and evidences were presented in favour of a dominant exocyclic enol form in the five- and an endocyclic enol form in the six-, seven- and eight-membered ring systems.
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    URL: http://dx.doi.org/10.1007/BF00809360
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    Geometry versus basicity of bilatrienes: Stretched and helical protonated biliverdins (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 495-506 
    Details
    ISSN: 1434-4475
    Keywords: Protonated biliverdins ; Conformation dependent basicity ; Bridged biliverdins ; pK a-Values ; UV-VIS ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Leichtigkeit der Protonierung von Biliverdinen am Pyrrolenin-Stickstoff hängt von ihrer Konformation ab. Das Biliverdin2, das durch eine viergliedrige Brücke in einer helikalen (Z, Z, Z, syn, syn, syn-Geometrie festgehalten wird, ist um ca. drei Größenordnungen weniger basisch als flexible offenkettige Bilatriene, wie der Biliverdin-IXα-dimethylester (1), der — wie gezeigt wird — in seiner monoprotonierten Form eine gestreckte Konformation einnimmt. Diese Ergebnisse werden durch eine vergleichende Untersuchung der Titrationen von1 und2 mit Schwefelsäure in Methanol bzw. Methanol-Wasser-Gemischen mithilfe der UV-VIS- und NMR-Spektroskopie erhalten.
    Notes: Summary The ease of protonation of bilatrienes at the pyrrolenine nitrogen critically depends on their conformation. The biliverdin2 being constrained to a helical (Z, Z, Z, syn, syn, syn) geometry by its four link chain is ca. three orders of magnitude less basic than flexible open-chain bilatrienes like biliverdin-IXα dimethyl ester (1), which is shown to adopt a stretched conformation in its monoprotonated form. These results are obtained by a comparative investigation of the titrations of1 and2 with sulfuric acid in methanol and methanol-water by means of UV-VIS and NMR spectroscopy.
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    URL: http://dx.doi.org/10.1007/BF00809802
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    Complete1H- and13C-NMR spectroscopic assignment of two pentadecapeptides by reverse C,H correlation techniques (1992)
    Springer
    Monatshefte für Chemie 123 (1992), S. 757-768 
    Details
    ISSN: 1434-4475
    Keywords: Virus ; Peptide ; NMR ; Assignment ; Reverse Techniques ; Conformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Zwei Oligopeptide, die die native Spaltregion für die Proteinase2 A des humanen Rhinovirus von Serotyp 2 (HRV 22 A) beziehungsweise eine modifizierte Version repräsentieren, wurden mit Hilfe von homo- und heterokorrelierter 2 D-NMR-Spektroskopie untersucht. Protondetektierte C,H-Korrelationstechniken erwiesen sich als außerordentlich hilfreich bei der sequenziellen Zuordnung. In einem Fall konnte das gesamte Aminosäureskelett ohne Zuhilfenahme von NOESY-Spektren analysiert und damit die dieser Methode inhärenten Unsicherheiten bei der Zuordnung vermieden werden. In keinem der beiden Moleküle konnte eine definierte Tertiärstruktur der Spaltregion ermittelt werden. Eines der beiden Oligopeptide liegt jedoch zu einem sehr geringen Prozentsatz in einer von derrandom-coil Anordnung abweichenden Konformation vor.
    Notes: Summary Two oligopeptides representing a wild type and a modified version of the polyprotein cleavage region for proteinase2 A of the human rhinovirus type 2 (HRV 22 A) have been investigated using homo- and heterocorrelated 2 D NMR spectroscopy. Proton-detected C,H correlation techniques turned out to be extremely useful for sequential resonance assignment. In one case, the complete amino acid backbone could be analyzed without using NOESY spectra, thus avoiding ambiguities inherent to this method. No defined tertiary structure of the cleavage region could be detected in either molecule. However, one of the oligopeptides is present to a very low extent in a conformation different from therandom-coil arrangement.
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    URL: http://dx.doi.org/10.1007/BF00812325
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    2D relayed15N,1H correlated NMR spectroscopy of a pentadecapeptide at natural abundance of15N (1993)
    Springer
    Monatshefte für Chemie 124 (1993), S. 333-337 
    Details
    ISSN: 1434-4475
    Keywords: Peptide ; NMR ; Nitrogen-15 ; Reverse Techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Anhand1H-detektierterrelayed-N,H-korrelierter NMR-Spektroskopie bei natürlicher Häufigkeit von15N wird die große Bedeutung der heteronuklearen Kernresonanzspektroskopie für die Protonenzuordnung mittlerer Oligopeptide demonstriert.
    Notes: Summary Proton-detected H-relayed N,H correlation NMR spectroscopy at natural abundance of15N has been used to demonstrate the enormous value of heteronuclear NMR spectroscopy for the proton assignment of medium-sized oligopeptides.
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    URL: http://dx.doi.org/10.1007/BF00810593
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    NMR spectroscopy of organophosphorus compounds II: Stereochemistry of [1-(2H-azirin-2-yl)alkyl]phosphonates (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 1101-1111 
    Details
    ISSN: 1434-4475
    Keywords: [1-(2H-Azirin-2-yl)alkyl]phosphonates ; Configuration ; Conformation ; Diastereotopy ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die detaillierte NMR-spektroskopische Untersuchung (1H,13C,15N,31P) einiger charakteristischer Vertreter von [1-(2H-Azirin-2-yl)alkyl]phosphonaten erlaubte es, Konformation und relative Konfiguration der betreffenden Verbindungen zu bestimmen. Die chemische Verschiebung des bezüglich des Phosphonatrests α-ständigen Protons kann als Kriterium zur Unterscheidung und stereochemischen Zuordnung von Diastereomeren herangezogen werden. Die Phänomenologie der NMR-Spektren wird im Zusammenhang mit strukturellen Parametern diskutiert.
    Notes: Summary The conformation and relative configuration of [1-(2H-azirin-2-yl)alkyl]phosphonates (2) has been established by thorough investigation of some characteristic representatives of the series by1H,13C,15N, and31P NMR spectroscopy. It is shown that the chemical shift of the proton located α to the phosphonate group can be used as a criterion for the discrimination and stereochemical assignment of diastereoisomers. NMR spectroscopic features of the compounds are discussed in terms of structural relationships.
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    URL: http://dx.doi.org/10.1007/BF00811518
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    Syntheses and spectroscopic studies of diphenylphosphinato derivatives of boron (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 607-613 
    Details
    ISSN: 1434-4475
    Keywords: Boron ; Diphenylphosphinato ; IR ; NMR ; B-11 ; P-31 ; Sn-119
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 2-Diphenylphosphinato-1,3,2-dioxaborolane und -borinane des Typs (mitG = -CH2CHMe-, -CH2CH2CH2-,-CH2CH2CHMe-, -CMe2CMe2-,-CMe2CH2CHMe-, -CH2CMe2CH2-, -CH2CEt2CH2- und C6H4) erhält man durch Reaktion von Diphenylphosphinsäure mit den entsprechenden 2,2′-Oxo-bis-1,3,2-dioxaborolanen und -borinanen. Die Produkte sind weiße, kristalline, hydrolyseunempfindliche Festkörper. Sie wurden mittels Elementaranalyse, IR-Spektroskopie und multinuklearer NMR-Spektroskopie (11B,31P und119Sn) charakterisiert. Die Resultate legen Strukturen mit monodentaten Phosphinatoeinheiten und dreifach koordinierten Boratomen nahe.
    Notes: Summary 2-Diphenylphosphinato-1,3,2-dioxaborolanes and -borinanes of the type (whereG = -CH2CHMe-, -CH2CH2CH2-, -CH2CH2CHMe-,-CMe2CMe2-, -CMe2CH2CHMe-,-CH2CMe2CH2-, -CH2CEt2CH2-, and -C6H4-) are obtained by the reaction of diphenylphosphinic acid with the corresponding 2,2′-oxo-bis-1,3,2-dioxaborolanes and-borinanes. The products are white crystalline solids, which have sharp melting points and are hydrolytically stable. They have been characterized by elemental analysis, IR and multinuclear NMR (11B,31P, and119Sn) studies. The data suggest structures with monodentate phosphinato moieties and 3-coordinated boron atoms.
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    Molecular Dynamic and Conformational Study of an Unsaturated 12-crown-S2O2 Ether and its AgI Complexes (1997)
    Springer
    Journal of molecular modeling 3 (1997), S. 355-358 
    Details
    ISSN: 0948-5023
    Keywords: Keywords: Thiocrown ether ; NMR ; Ag(I) complexes ; Molecular Dynamic simulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The preferred conformations and the complexional behaviour of mn-12S2O2 were studied by means of both NMR spectroscopy and molecular modelling. Furthermore, the AgI complexes of this ligand mn-12S2O2 were also studied by molecular mechanical calculations.
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    URL: http://dx.doi.org/10.1007/s008940050050
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    A1 H spin echo and 51V NMR study of the interaction of vanadate with intact erythrocytes (1997)
    Springer
    JBIC 2 (1997), S. 235-241 
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    ISSN: 1432-1327
    Keywords: Key words Vanadium ; Erythrocyte ; NMR ; Oxidative stress ; Diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The action of vanadate on intact human erythrocytes was studied by 1H spin echo and 51V NMR spectroscopy as a model for the behaviour of vanadium(V) complexes in experimental diabetes. Vanadate is reduced by the intact erythrocyte at the expense of intracellular glutathione which rapidly depletes from the intracellular volume. Using the blocking agent 4,4′-diisothio-cyanatostilbene-2,2′-disulfonic acid (DIDS), which specifically blocks the anion transporter, vanadate reduction could be inhibited and glutathione depletion arrested. Thus, for the reaction with the intact cell to occur, vanadium(V) must cross the cell wall, possibly via the anion transporter. Nitrofurantoin was used to inhibit glutathione reductase in the erythrocyte suspensions. Under these conditions, treatment of the cells with vanadate induced glutathione oxidation prior to depletion. A study of the reaction of vanadate with haemolysate indicates that, without the influence of the membrane, rapid oxidation of glutathione to glutathione disulfide by the vanadyl cation occurs with no glutathione depletion, and that under these conditions vanadate reduction is incomplete. This study generates a model for the behaviour of vanadium complexes in vivo, providing a basis for the rational design and synthesis of new vanadium-based agents as insulin mimics. In essence, vanadium is transported across the membrane as vanadate(V), is reduced in situ by glutathione, and becomes complexed to a wide range of intracellular binding sites. Exchange reactions between glutathione and sulfhydryl groups present on haemoglobin and membrane lead to the depletion of glutathione from the cytosol.
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    URL: http://dx.doi.org/10.1007/s007750050129
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    The use of pseudocontact shifts to refine solution structures of paramagnetic metalloproteins: Met80Ala cyano-cytochrome c as an example (1996)
    Springer
    JBIC 1 (1996), S. 117-126 
    Details
    ISSN: 1432-1327
    Keywords: Key words Solution structure ; Paramagnetic biomolecules ; NMR ; Cytochrome c
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The availability of NOE constraints and of the relative solution structure of a paramagnetic protein permits the use of pseudocontact shifts as further structural constraints. We have developed a strategy based on: (1) determination of the χ tensor anisotropy parameters from the starting structure; (2) recalculation of a new structure by using NOE and pseudocontact shift constraints simultaneously; (3) redetermination of the χ tensor anisotropy parameters from the new structure, and so on until self-consistency. The system investigated is the cyanide derivative of a variant of the oxidized Saccharomyces cerevisiae iso-1-cytochrome c containing the Met80Ala mutation. The structure has been substantially refined. It is shown that the analysis of the deviation of the experimental pseudocontact shifts from those calculated using the starting structure may be unsound, as may the simple structure refinement based on the pseudocontact shift constraints only.
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    URL: http://dx.doi.org/10.1007/s007750050030
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    Modulation of Bacillus pasteurii cytochrome c 553 reduction potential by structural and solution parameters (1998)
    Springer
    JBIC 3 (1998), S. 371-382 
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    ISSN: 1432-1327
    Keywords: Key words Bacillus pasteurii ; cytochrome c553 ; electrochemistry ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Direct cyclic voltammetry and 1H NMR spectroscopy have been combined to investigate the electrochemical and spectroscopic properties of cytochrome c 553 isolated from the alkaliphilic soil bacterium Bacillus pasteurii. A quasi-reversible diffusion-controlled redox process is exhibited by cytochrome c 553 at a pyrolitic graphite edge microelectrode. The temperature dependence of the reduction potential, measured using a non-isothermal electrochemical cell, revealed a discontinuity at 308 K. The thermodynamic parameters determined in the low-temperature range (275–308 K;ΔS°′=–162.7±1.2 J mol–1 K–1, ΔH°′=–53.0±0.5 kJ mol–1, ΔG°′=–4.5±0.1 kJ mol–1, E°′=+47.0±0.6 mV) indicate the presence of large enthalpic and entropic effects, leading, respectively, to stabilization and destabilization of the reduced form of cytochrome c 553. Both effects are more accentuated in the high-temperature range (308–323 K;ΔS°′=–294.1±8.4 J mol–1 K–1, ΔH°′=–93.4±3.1 kJ mol–1, ΔG°′=–5.8±0.6 kJ mol–1, E°′=+60.3±5.8 mV), with the net result being a slight increase of the standard reduction potential. These thermodynamic parameters are interpreted using the compensation theory of hydration of biopolymers as indicating the extrusion, upon reduction, of water molecules from the hydration sphere of the cytochrome. The low-T and high-T conformers differ by the number of water molecules in the solvation sphere: in the high-T conformer, the number of water molecules extruded upon reduction increases, as compared to the low-T conformer. The ionic strength dependence of the reduction potential at 298 K, treated within the frame of extended Debye-Hückel theory, yields values of E °′ (I=0) =–25.4±1.4 mV, z red=–11.3, and z ox=–10.3. The pH dependence of the reduction potential at 298 K shows a plateau in the pH range 7–10 and an increase at more acidic pH, allowing the calculation of pK O=5.5 and pK R=5.7, together with the estimate of the reduction potentials of completely protonated (+71 mV) and deprotonated (+58 mV) forms of cytochrome c 553. 1H NMR spectra of the oxidized paramagnetic cytochrome c 553 indicate the presence of a His-Met axial coordination of the low-spin (S=1/2) heme iron, which is maintained in the temperature interval 288–340 K at pH 7 and in the pH range 4.8–10.0 at 298 K. The temperature dependence of the hyperfine-shifted signals shows both Curie-type and anti-Curie-type behavior, with marked deviations from linearity, interpreted as indicating the presence of a fast equilibrium between the low-T and high-T conformers, having slightly different heme electronic structures resulting from the T-induced conformational change. Increasing the NaCl concentration in the range 0–0.2 M causes a slight change of the 1H NMR chemical shifts of the hyperfine-shifted signals, with no influence on their linewidth. The calculated lower limit value of the apparent affinity constant for specific ion binding is estimated as 5.2±1.1 M–1. The pH dependence of the isotropically shifted 1H NMR signals of the oxidized cytochrome displays at least one ionization step with pK O=5.7. The thermodynamic and spectroscopic data indicate a large solvent-derived entropic effect as the main cause for the observed low reduction potential of B. pasteurii cytochrome c 553.
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    The effect of axial ligand plane orientation on the contact and pseudocontact shifts of low-spin ferriheme proteins (1998)
    Springer
    JBIC 3 (1998), S. 581-594 
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    ISSN: 1432-1327
    Keywords: Key words Heme protein ; NMR ; paramagetic ; contact ; pseudocontact ; axial ligand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The effect of axial ligand nodal plane orientation on the contact and pseudocontact shifts of a symmetrical low-spin octamethylferriheme center has been calculated as a function of the angle of the axial ligand. Simple Hückel techniques have been used to estimate the contact contribution, and values obtained from model hemes, together with counter-rotation of the g-tensor, have been used to estimate the pseudocontact contribution, for the eight β-pyrrole methyl and four meso-H positions. It is found that the maximum and minimum contact shifts occur when the axial ligand is aligned at an angle of ±15° to the meso-H axes of the heme, rather than when the axial ligand plane lies along the porphyrin nitrogens, as assumed previously by some investigators. For systems having one planar axial ligand or two ligands in parallel planes, the contact and pseudocontact contributions at the meso-H positions are comparable in size (at least on the basis of simple Hückel estimates), while the contact contribution clearly dominates the isotropic shifts of the heme methyls. Allowing for the substituent effect of the 2,4-vinyls of protohemin, or the 2,4-thioethers of hemin c, as well as the average diamagnetic shifts of the heme methyls and meso-H, plots of the predicted shifts as a function of axial ligand nodal plane orientation have been constructed for hemin b- and c-containing proteins. Excellent agreement in the order of shifts, and reasonable agreement in the sizes of the observed shifts, is observed in the majority of the ferriheme proteins for which the methyl and meso-H resonances have been assigned and proton shifts reported. Plots have also been constructed for hemin c-containing proteins having the two axial ligand nodal planes oriented at relative angles of 40°, 70°, and 80°. Excellent agreement in the order of shifts, and reasonable agreement in the magnitudes of the observed shifts, is observed in all cases of bacterial cytochromes which do not fit the plots that assume the ligands are in parallel planes, except one – the cytochrome c-552 of Nitrosomonas europae. Except for this case, where the order of the predicted methyl shifts at any angle of the axial ligands disagrees with the observed, the reasons can usually be attributed to a large dihedral angle between two axial ligand nodal planes, to strong H-bonding interactions involving His and/or CN– ligands, or to off-axis binding of one (or both) axial ligand(s). Ruffling of the porphyrin ring may also contribute to the contact shift in as yet undefined ways. Hence, despite the simplicity of the calculations, the agreement with observed data is highly satisfying and the concept of the importance of axial ligand plane orientation on the observed proton shifts of heme proteins is fully confirmed.
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    Solution structure of reduced horse heart cytochrome c (1999)
    Springer
    JBIC 4 (1999), S. 21-31 
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    ISSN: 1432-1327
    Keywords: Key words Reduced cytochrome c ; Solution structure ; NMR ; Heme proteins ; Electron transfer proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  In the frame of a broad study on the structural differences between the two redox forms of cytochromes to be related to the electron transfer process, the NMR solution structure of horse heart cytochrome c in the reduced form has been determined. The structural data obtained in the present work are compared to those already available in the literature on the same protein and the presence of conformational differences is discussed in the light of the experimental method employed for the structure determination. Redox-state dependent changes are analyzed and in particular they are related to the role of propionate-7 of the heme. Also some hydrogen bonds are changed upon reduction of the heme iron. A substantial similarity is observed for the backbone fold, independently of the oxidation state. At variance, some meaningful differences are observed in the orientation of a few side chains. These changes are related to those found in the case of the highly homologous cytochrome c from Saccharomyces cerevisiae. The exchangeability of the NH protons has been investigated and found to be smaller than in the case of the oxidized protein. We think that this is a characteristic of reduced cytochromes and that mobility is a medium for molecular recognition in vivo.
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    URL: http://dx.doi.org/10.1007/s007750050285
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    Interaction of cis- and trans-RuCl2(DMSO)4 with the nucleotides GpA, d(GpA), ApG, d(ApG) and d(CCTGGTCC): high-field NMR characterization of the reaction products (1999)
    Springer
    JBIC 4 (1999), S. 199-208 
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    ISSN: 1432-1327
    Keywords: Key words Ruthenium ; Nucleotides ; Dimethyl sulfoxide ; Anticancer ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Both cis- and trans-RuCl2(DMSO)4 (cis-Ru and trans-Ru) react with ApG, GpA, d(ApG) and d(GpA) to yield products with bifunctional metal coordination of the bases. For each dinucleotide one major product and several minor species are formed. This is in contrast to previous results on analogous reactions between trans-Ru and d(GpG) where a substantial amount of an intermediate species was found. The rates of reaction between dinucleotides and cis-Ru are approximately 20-fold slower than for trans-Ru. The compounds formed with the two isomers exhibit identical proton NMR spectra, suggesting the same coordination mode for ruthenium in the final product. The two purine bases are coordinated to ruthenium through N7 in a head-to-head conformation with the glycosidic angles being in the anti range. Coupling constants indicate a relatively pure 3′-endo conformation for the 5′-sugar and mainly 2′-endo for the 3′-sugar. The similar bifunctional binding mode of cis- and trans-Ru(II) with dinucleotides as evident from the NMR spectra are in contrast to the different mode of interaction suggested earlier for cis- and trans-Ru complexes with DNA. trans-Ru interacts with the deoxyoctanucleotide d(CCTGGTCC), giving two main products during the first 2 h of incubation time. Four H8 guanine resonances are shifted downfield, characteristic of N7 metal coordination. The products are not analyzed in detail, but it is suggested that the structures may be described as two chiral G(N7/N7) chelates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050305
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  • 90
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    1H NMR studies of the Fe7S8 ferredoxin from Bacillus schlegelii: a further attempt to understand Fe3S4 clusters (1996)
    Springer
    JBIC 1 (1996), S. 523-528 
    Details
    ISSN: 1432-1327
    Keywords: Key words Ferredoxin ; Iron-sulfur clusters ; NMR ; Hyperfine shifts ; Magnetic interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The oxidized Fe7S8 ferredoxin from Bacillus schlegelii, containing both [Fe3S4]+ and [Fe4S4]2+ clusters, has been investigated by 1H NMR spectroscopy. An extensive sequence-specific assignment of the hyperfine-shifted resonances has been obtained by making use of a computer-generated structural model. The pattern and the temperature dependence of the hyperfine shifts of the β-CH2 protons of the cysteines coordinating the [Fe3S4]+ cluster are rationalized in terms of magnetic interactions between the iron ions. The same approach holds for the hyperfine coupling with 57Fe. It is shown that the magnetic interactions are more asymmetric in Fe7S8 ferredoxins than in Fe3S4 ferredoxins. The NMR non-observability of the β-CH2 protons of coordinated cysteines in the one-electron-reduced form has been discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050087
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  • 91
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    A 29Si MAS-NMR study of Cd7[Ge6Si]O21 pyroxmangite (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 713-718 
    Details
    ISSN: 1432-2021
    Keywords: Key words Cd-pyroxmangite ; NMR ; Pyroxenoids ; Ordering ; Superperiods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Synthetic (SiGe)-pyroxenoids are often observed to have superperiods. Whether or not these superperiods grow in connection with Si-Ge ordering is a fundamental question. The size difference between Ge and Si tetrahedra leads to CdGeO3 having the pyroxmangite structure, whereas CdSiO3 has the wollastonite structure. Consequently, considerable strain is expected for a pyroxenoid with a disordered Ge-Si distribution. A 29Si MAS-NMR study of a Cd-pyroxmangite of nominal composition Cd7[Ge6Si]O7 points to considerable Si clustering, probably as GeSiSiSiGe triples corresponding to the wollastonite-like units of the siebener chain. It is proposed that such ordering relieves strain within the tetrahedral chain. Residual strain is also relieved by insertion of an extra pair of GeO4 tetrahedra into the pyroxene-like component of the siebener-chain units, leading to single neuner-chain units which terminate the superperiods. This growth pattern is cyclic. The presence of several types of superperiod may reflect similar energetics for different Ge-Si-ordering patterns within the siebener chains. Ordering of Si-rich unit cells and of unit cells having no Si is proposed as the reason for the occurrence of the superperiods in Cd-pyroxmangite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690000115
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  • 92
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    Measure theoretic imaging, with an example employing magnetic resonance input (1988)
    Springer
    Machine vision and applications 1 (1988), S. 169-174 
    Details
    ISSN: 1432-1769
    Keywords: measure theory ; computed tomography ; imaging ; NMR ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We present a new medical imaging principle which allows reconstruction of images (from the output of a general digital imaging technology) whose contrast is based on a fundamentally different mathematical mechanism than that of standard images. These images have the useful property that they are capable of exhibiting high contrast between tissues which in currently produced images necessarily have low contrast. The meaning of these images, and their general place in the context of present image generation techniques, is most naturally expressed in the formalism of measure theory. The property actually imaged is derived from a probability measure associated with the mapping which expresses the output of the imaging technology. It also has a nonprobabilistic interpretation as a generalization of the Jacobian, specifically, the Radon-Nikodym derivative. In particular, unlike standard images, contrast is independent of the metric in the space of physical signals that the imaging technology associates with points of the region to be imaged. Images based on this approach using magnetic resonance input are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01213004
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  • 93
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    Site-directed mutagenesis of a phenylalanine residue strictly conserved in cytochromes c 3 (1996)
    Springer
    JBIC 1 (1996), S. 542-550 
    Details
    ISSN: 1432-1327
    Keywords: Key words Cytochrome c3 ; Mutagenesis ; Redox-Bohr ; NMR ; EPR ; Cooperativity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Reduction of the haems in tetrahaem cytochromes c 3 is a cooperative process, i.e., reduction of each of the haems depends on the redox states of the other haems. Furthermore, electron transfer is coupled to proton transfer (redox-Bohr effect). Two of its haems and a strictly conserved nearby phenylalanine residue, F20, in Desulfovibrio vulgaris (Hildenborough) cytochrome c 3 form a structural motif that is present in all cytochromes c 3 and also in cytochrome c oxidase. A putative role for this phenylalanine residue in the cooperativity of haem reduction was investigated. Therefore, this phenylalanine was replaced, with genetic techniques, by isoleucine and tyrosine in D. vulgaris (Hildenborough) cytochrome c 3. Cyclic voltammetry studies revealed a small increase (30 mV) in one of the macroscopic redox potentials in the mutated cytochromes. EPR showed that the main alterations occurred in the vicinity of haem I, the haem closest to residue 20 and one of the haems responsible for positive cooperativities in electron transfer of D. vulgaris cytochrome c 3. NMR studies of F20I cytochrome c 3 demonstrated that the haem core architecture is maintained and that the more affected haem proton groups are those near the mutation site. NMR redox titrations of this mutated protein gave evidence for only small changes in the relative redox potentials of the haems. However, electron/electron and proton/electron cooperativity are maintained, indicating that this aromatic residue has no essential role in these processes. Furthermore, chemical modification of the N-terminal amino group of cytochrome c 3 backbone, which is also very close to haem I, had no effect on the network of cooperativities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050090
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  • 94
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    The solution structure of a monomeric, reduced form of human copper,zinc superoxide dismutase bearing the same charge as the native protein (1999)
    Springer
    JBIC 4 (1999), S. 795-803 
    Details
    ISSN: 1432-1327
    Keywords: NMR ; Superoxide dismutase ; Solution structure ; Monomeric mutants ; Structure-function relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: 2 , has RMSD values with respect to the average structure of 0.94 ± 0.14 Å2 and 1.50 ± 0.14 Å2 for the backbone and the heavy atoms, respectively. The overall folding, which includes the classical eight-stranded Greek-key β-barrel and a short α-helix, is very close to that of the previously characterized monomeric mutant E133QM2SOD and to that of wild-type SOD. The region involved in the subunit-subunit interactions in the dimeric protein is confirmed to be disordered in the monomeric species. It is also observed that a sizable rearrangement of the charged groups of the electrostatic loop and of Arg143 takes place in the monomeric species. The width of the active site channel, both at its entrance and at the bottleneck of the active site, is discussed in the light of the influence on the enzymatic activity and the latter with respect to the overall charge. It is also confirmed that the NH proton of His63 shields the Cu(I) from the bulk solvent, thus supporting the suggestion that superoxide may interact with the reduced metal ion in an outer-sphere fashion.
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    URL: http://dx.doi.org/10.1007/s007750050353
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  • 95
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    Reevaluation of the redox and redox-Bohr cooperativity in tetrahaem Desulfovibrio vulgaris (Miyazaki F) cytochrome c 3 (1997)
    Springer
    JBIC 2 (1997), S. 343-349 
    Details
    ISSN: 1432-1327
    Keywords: Key words Cooperativity ; Cytochrome c3 ; NMR ; Paramagnetic ; Redox-Bohr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The thermodynamic model of five interacting charge centres (four haems and an ionisable centre), which was used in the characterisation of the thermodynamic properties of Desulfovibrio vulgaris (Hildenborough) cytochrome c 3 (c 3DvH), is now used to reevaluate the thermodynamic properties in Desulfovibrio vulgaris (Miyazaki F) cytochrome c 3 (c 3DvM) on the basis of published data (Park, J.-S., Ohmura, T., Kano, K., Sagara, T., Niki, K., Kyogoku, Y. and Akutsu, H. (1996) Biochim. Biophys. Acta 1293, 45–54). Contrary to the assertion of Park et al. (1996), the pH dependence of the proton chemical shifts of haem methyls in c 3DvM in several stages of oxidation is well described by the model, which involves both homotropic (e–/e–) and heterotropic (e–/H+) cooperativity. This shows that the pH dependence observed for c 3DvM is not significantly more complicated than that observed for c 3DvH. Since the parameters which we now obtain for c 3DvM are generated with the same model as those from c 3DvH, albeit using less precise data, it is possible to make a preliminary comparison of the thermodynamic properties of these two proteins and of their role in energy transduction. The extrinsic dipolar shifts generated for each methyl group by each of the four haems in c 3DvM are also determined. A novel method for approximating the magnetic susceptibility tensors is used: the orientations of the principal axes of the tensors have been shown to be closely related to the geometry of the axial ligands, which is available from the X-ray structure of c 3DvM, and the components of the tensors are extrapolated from EPR g values. The inclusion of the calculated haem extrinsic contributions clearly describes the pH dependence of the haem methyls in the core of the protein, close to other haems. This description is most remarkable in the case of the haem methyl 21CH3 II I, for which the "unusual pH dependence" commented on by Park et al. (1996) is easily explained using the thermodynamic parameters determined by our model together with the calculated extrinsic dipolar shifts, thus providing a test of the analysis.
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    URL: http://dx.doi.org/10.1007/s007750050141
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  • 96
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    Metal-binding and active-site structure of di-zinc Streptomyces griseus aminopeptidase (1997)
    Springer
    JBIC 2 (1997), S. 744-749 
    Details
    ISSN: 1432-1327
    Keywords: Key words Aminopeptidase ; Streptomyces ; Dinuclear ; NMR ; Co2+ ; Cu2+
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Streptomyces griseus aminopeptidase has been characterized to have a dinuclear active site and to follow a dinuclear hydrolytic mechanism by means of activity assay, optical, and NMR spectroscopy. A sequential binding of Co2+ to the dinuclear sites in 20 mM Mes buffer at pH 6.1 has also been established. The results from these studies suggest that the two metal sites have a five-coordination sphere, with at least one coordinated His each. A di-Cu2+-substituted derivative of the enzyme has been prepared which exhibits a 1H NMR spectrum with sharp hyperfine-shifted signals, again indicating the presence of a dinuclear active site. This 1H NMR spectrum with sharp hyperfine-shifted features represents a first of its kind for a di-Cu2+ center in metalloproteins.
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    URL: http://dx.doi.org/10.1007/s007750050190
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  • 97
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    Structure of the three-haem core of cytochrome c 551.5 determined by 1H NMR (1996)
    Springer
    JBIC 1 (1996), S. 305-311 
    Details
    ISSN: 1432-1327
    Keywords: Key words Multihaem cytochromes ; Cytochrome c551.5 ; Cytochrome c3 ; Sulfate-reducing bacteria ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The trihaem cytochrome c 551.5, formerly known as cytochrome c 7, from the organism Desulfuromonas acetoxidans, has been studied in the reduced state by 2D proton NMR. The haem proton resonances were assigned, and several nuclear Overhauser enhancements (NOEs) between resonances arising from different haems were detected and assigned. The relative orientations of the three haems were calculated by fitting both the intensities of the interhaem NOEs and the magnitudes of the ring current shifts of the haem resonances, following the strategy previously used by the authors to reassess the X-ray structure of the haem core in tetrahaem cytochrome c 3 from Desulfumicrobium baculatum. It is concluded that, although the comparison of the protein sequence with those of the tetrahaem cytochromes c 3 shows that in cytochrome c 551.5 about 40% of the sequence is deleted, including the region involved in the attachment of the second of the four haems, this does not induce any significant rearrangement of the remaining three haems other than a slight decrease in the iron-iron distance between two of the haems, namely those corresponding to haems I and IV of cytochrome c 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050058
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  • 98
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    Characterization of cytochrome c 6 from the cyanobacterium Anabaena PCC 7119 (1997)
    Springer
    JBIC 2 (1997), S. 225-234 
    Details
    ISSN: 1432-1327
    Keywords: Key words Cytochrome c6 ; Anabaena PCC 7119 ; EPR ; NMR ; Redox-Bohr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  A soluble monoheme c–type cytochrome c 6 has been isolated from the cyanobacterium Anabaena PCC 7119. It is a basic protein, with a molecular mass of 9.7 kDa, which accepts electrons from Anabaena ferredoxin in the ferredoxin-NADP+reductase-dependent NADPH cytochrome c reductase activity assay. The turnover of the reaction has an optimum pH at 7.5. Flavodoxin can also replace ferredoxin in this assay, but with only 20% efficiency. Plastocyanin from Anabaena PCC 7119, as well as the c 6 cytochromes from the green algae Chlorella fusca and Monoraphidium braunii are also shown to accept electrons from Anabaena ferredoxin. The reduction potential of cytochrome c 6 at pH 6.7 was determined to be 338 mV and is pH dependent, with pK a ox=8.4±0.1 and pK a red≈9.5. The ferric and ferrous cytochrome forms and their pH equilibria have been studied using visible, EPR and 1H-NMR spectroscopies. The amino acid sequence and the visible and NMR spectroscopic data indicate that the heme iron has a methionine-histidine axial coordination in the pH range 5–11. However, the EPR data for the ferricytochrome are complex and show that in this pH range five distinct forms are present. Between pH 5 and 9 the spectrum is dominated by two rhombic species, with g–values at 2.94, 2.29, 1.43 and at 2.84, 2.34, 1.56, which interconvert with a pK a of 8.4. The NMR data also show a main interconversion between two cytochrome forms at this pH, which coincides with that determined from the pH dependence of the reduction potential. Both these forms were associated with a methionine-histidine heme-iron coordination by correlation with the visible and NMR spectral data, although having crystal field parameters atypical for this type of coordination. Anabaena cytochrome c 6 is one more example of a heme protein for which the widely used crystal field analysis of the EPR data (truth diagram) fails to unequivocally determine the type of heme-iron ligation.
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    URL: http://dx.doi.org/10.1007/s007750050128
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    A MINDO/3 MO study of oxidized flavins (1981)
    Springer
    Theoretical chemistry accounts 60 (1981), S. 127-141 
    Details
    ISSN: 1432-2234
    Keywords: Flavins ; Isoalloxazines ; MINDO/3 ; NMR ; Energies ; Dipole moments ; Ionization potentials ; Electron affinities ; Semiempirical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The use of semi-empirical molecular orbital methods for the study of biologically important molecules has increased in recent years. The validity of well-known approximate Hartree-Fock molecular orbital methods such as MINDO/3 and MNDO still remains largely untested for biological molecules. Here we report its first application to the study of the electronic structures of isoalloxazines. Electronic charge distribution, variation of dipole moment, first ionization potential, electron affinity, orbital energies and electronic transitions are examined. Some of these results are compared with experiments. Good correlations with experiments were generally found in net atomic charge distributions, ionization potentials and electronic transitions. As a result of relatively good correlations with experiment application of the MINDO/3 method for extended study of biologically important coenzymes is promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550331
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  • 100
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    Direct computation of second-order SCF properties of large molecules on workstation computers with an application to large carbon clusters (1992)
    Springer
    Theoretical chemistry accounts 83 (1992), S. 455-470 
    Details
    ISSN: 1432-2234
    Keywords: Direct ; CPHF ; GIAO ; Polarizability ; NMR ; Magnetic shielding ; Carbon ; C60 ; C70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ab initio SCF computation of second-order properties of large molecules (with 50 atoms or more) on workstation computers is demonstrated for static dipole polarizabilities and nuclear magneting shieldings. The magnetic shieldings are calculated on the basis of gauge including atomic orbitals (GIAO). Algorithmic advances (semi-direct algorithms with efficient integral pre-screening, and use of a quadratically convergent functional for the polarizabilities) are presented together with an illustrative application to the fullerenes C60 and C70.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113068
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