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  • Chemistry  (11)
  • 2020-2022
  • 1990-1994  (11)
  • 1935-1939
  • 1
    Electronic Resource
    Electronic Resource
    Surface chemical changes of mixed-oxide films in Cl2 anodic production (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 887-890 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The recent development of specific and sensitive surface techniques has prompted new studies of electrode properties, in particular of their catalytic activity. Many papers have reported the use of X-ray photoelectron spectrometry, Rutherford backscattering spectrometry, secondary ion mass spectrometry etc. in the analysis of mixed-oxide films, and interesting results concerning electrochromic and catalytic properties have been shown. The influence of the method of preparation has also been confirmed, together with the important role of microstructural composition. In previous studies, our group performed composition analyses and depth profiles of RuO2/TiO2 and IrO2/TiO2 mixed-oxide coatings by secondary ion mass spectrometry (SIMS). Many positive-and negative-ion species are of particular interest in characterizing electrodes synthesized by different methods. This paper presents the results obtained by SIMS analysis of IrO2/RuO2/TiO2 films before and after their use in CI2 anodic production. Mass spectra obtained under different experimental conditions are reported and the aspects related to surface compositon modifications induced by Cl2 evolution on electrode films are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071006
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  • 2
    Electronic Resource
    Electronic Resource
    Secondary-ion mass spectrometry methodology and surface chemistry of mixed oxide electrodes: Modifications induced by noble-metal content (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 659-665 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mixed-oxide coatings are extensively used in the electrochemical industry. Secondary-ion mass spectrometric data confirm that technological research can indeed find a new way of controlling precursors, synthesis conditions, purity of coatings and electrodic activity. Results obtained by argon and oxygen primary-ion bombardment of RuO2/TiO2, IrO2/TiO2, RuO2/IrO2/TiO2 films are reported. The presence of metal, metal oxide and cluster ions suggests a more systematic use of secondary-ion mass spectrometry in the elucidation of catalytic aspects. In-depth profiles of some ionic species and their correlation with parameters that induce significant modifications can help in the understanding of the solid state physics and inorganic chemistry involved.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080817
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and spectroscopic characterization of R3SnIV derivatives of N-acetyldipeptides (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 7 (1993), S. 243-252 
    Details
    ISSN: 0268-2605
    Keywords: Organotin ; biocidal ; biological ; Mössbauer ; NMR ; IR ; peptide ; protein ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Triorganotin(IV) derivatives of N-acetyldipeptides R3SnAcDip; R=Me, Et, n-Bu, n-Oct, Cy or Ph (HAcDip=N-acetylglycylglycine and N-acetylglycylvaline; R=Me, n-Bu, Cy, HAcDip=N-acetylglycylalanine) were obtained by neutralization of R3SnOH and HAcDip. The complexes were studied by means of 119Sn Mössbauer, IR and 1H, 13C and 119Sn NMR spectroscopy. The C—Sn—C bond angles have been inferred by rationalization of Mössbauer nuclear quadrupole splittings as well as from NMR coupling constants. Correlations of Mössbauer isomer shifts with partial atomic charges on tin atoms have been determined: Polymeric trigonal bipyramidal structures, with near-planar R3Sn units and axial carboxylate (unidentate) and C=O amide donor groups are inferred for all the compounds in the solid state, except for Cy3SnAcGlyVal for which a tetrahedral structure is proposed. In solution the complexes are monomeric; in methanol a solvent molecule is coordinated to tin which then is still in a trigonal bipyramidal environment.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590070404
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  • 4
    Electronic Resource
    Electronic Resource
    Extracellular sodium is required for methacholine-induced secretion of mucus glycoconjugates from canine tracheal explants (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 8 (1990), S. 171-175 
    Details
    ISSN: 0263-6484
    Keywords: Mucus ; glycoconjugate ; secretion ; canine ; trachea ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Extracellular sodium is known to influence secretion by certain secretory cells, possibly by mobilizing calcium from cellular stores or by altering intracellular pH via regulation of a Na+ -H+ antiport system. Using canine tracheal explants, we determined whether agents which alter sodium fluxes are capable of modulating basal or cholinergically-induced secretion of mucus glycoconjugates. Methacholine, a cholinergic agonist, increased mucus secretion from explants incubated in the presence or absence of calcium, but had no effect on secretion when incubated in sodium-deficient media, indicating (a) that cholinergically-induced secretion can be mediated by mobilization of cellular calcium and (b) that extracellular sodium was required for this stimulatory effect. Several agents which increase intracellular sodium were tested for their effect on mucus secretion. Ouabain, a sodium pump inhibitor, and veratridine, a sodium channel activator, did not significantly affect control or methacholine-induced secretion; gramicidin, a sodium ionophore, also had no effect on basal release. Tetrodotoxin, a sodium channel inhibitor, was also without effect on basal or methacholine-stimulated mucus release. Agents which alter intracellular pH were also examined for their effects on basal or methacholine-induced glycoconjugate secretion. Amiloride, which decreases intracellular pH by inhibiting Na+ -H+ exchange, produced a 19 per cent increase in basal secretion (not statistically significant), but had no effect on methacholine-induced secretion. An agent, 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS), which decreases intracellular pH by inhibiting HCO3--Cl- exchange, elicited decreases in both basal and methacholine-induced secretion, but the inhibition did not reach statistical significance. Thus extracellular sodium is required for cholinergically-induced glycoconjugate secretion from canine tracheal explants and the underlying mechanism does not involve sodium influx into the cell, but may possibly be mediated by alterations in intracellular pH.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cbf.290080308
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  • 5
    Electronic Resource
    Electronic Resource
    Semi-empirical MNDO study of the structure of some diorganotin (IV) glycylglycinates (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 7 (1993), S. 495-497 
    Details
    ISSN: 0268-2605
    Keywords: Organotin ; glycylglycinates ; structures ; MNDO calculations ; tin atomic charge ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The geometrical structures of some diorganotin glycylglycinates have been obtained using the MNDO semi-empirical method. A good agreement with the experimental diffractometric data was found.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590070708
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  • 6
    Electronic Resource
    Electronic Resource
    Stannacycloalkyl and stannepinyl derivatives of dipeptides (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 113-117 
    Details
    ISSN: 0268-2605
    Keywords: Organotin ; stannacycloalkyl compounds ; dipeptides ; Mössbauer ; NMR ; IR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stannacyclohexyl and stannacycloheptyl derivatives of dipeptides (CH2)nSnAA · xH2O (H2AA = H2GlyGly, with n = 5, x = 2 or n = 6, x = 1; H2AA = H2GlyAla, H2GlyVal, H2GlyMet, with n = 5, 6, x = 1) and stannepinyl glycylglycinate monohydrate have been obtained by the reaction of (CH2)nSnCl2 or stannepinyl dichloride with Na2AA. According to infrared and 119Sn Mössbauer data of the solid compounds, AA acts as a tridentate ONN ligand and tin has a trigonalbipyramidal environment. An analogous structure has been inferred from 1H, 13C, and 119Sn NMR data for the undissociated molecules in methanol solution.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080206
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and spectroscopic characterization of dimethyl-, di-n-butyl-, di-t-butyl-and diphenyl-tin(iv) derivatives of dipeptides: Crystal and molecular structure of di-n-butyltin(iv) glycylvalinateDedicated to Prof. Dr. Mult. Dr. h.c. Alois Haas (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 6 (1992), S. 83-94 
    Details
    ISSN: 0268-2605
    Keywords: Organotin ; dipeptides ; structures ; X-ray diffraction ; NMR ; Mössbauer ; infrared ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dipeptide complexes R2SnL listed below have been synthesized: (a) Me2SnL; H2L = glycylalanine (H2GlyAla), glycylvaline (H2GlyVal), glycylmethionine (H2GlyMet), glycyltryptophan (H2GlyTrp), glycyltyrosine (H2GlyTyr); (b) nBu2SnL; H2L = H2GlyAla, H2GlyVal; (c) nBu2SnL.H2O; H2L = glycylglycine (H2GlyGly), H2GlyAla; (d) tBu2SnL; H2L = H2GlyAla, H2GlyVal; (e) tBu2SnGlyGly. H2O; (f) Ph2SnL; H2L = H2GlyAla, H2GlyVal, H2GlyTyr, H2GlyTrp; (g) Ph2Sn(HGlyVal)2. The crystal and molecular structures of nBu2SnGl Val have been determined by single-crystal X-ray diffraction. The polyhedron around tin is a distorted trigonal bipyramid, analogous to that of Et2SnGlyTyr (see Vornefeld et al., Appl. Organomet. Chem., 1992, 6: 75). According to infrared and 119Sn (ΔE parameters) Mössbauer spectroscopic data the R2SnL derivatives can be classified by their solid-state structure into two types which are distinguished by the nature of the axial carboxylate [(i) monodentate, as in nBu2SnGlyVal; (ii) bidentate]. Bonding in R2SnL.H2O and Ph2Sn(HGlyVal)2 has been discussed on the basis of vibrational data. Rationalization of the 119Sn Mössbauer parameters has been attempted by ‘literal’ point-charge model, calculations of ΔE in the structural context described above. According to 13C NMR spectra, compounds Me2SnL are undissociated in methanol solutions, whilst dissociation is inferred for aqueous solutions, probably concerning the carboxyl and amino groups only. Five-coordination in methanol and aqueous solutions has been assumed for Me2Snl from 119Sn NMR chemical shifts. Values of coupling constants |2J(119Sn, 1H)|, determined from 1H NMR spectra, gave estimates of C—Sn—C angles in Me2SnL in the range 128-136° in methanol and aqueous solutions, which correspond to values from 119Sn Mössbauer ΔE parameters (129.6-133.8°). The structural relationship of R2SnL molecules in the solid state and in solution phase has been discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590060111
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and spectroscopic characterization of diethyltin (IV) derivatives of dipeptides: Crystal and molecular structure of diethyltin glycyltrosinateThis paper is dedicated to Prof. Dr. Peter Sartori with appreciation.Further X-ray structure determination data is available from the authors. (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 6 (1992), S. 75-82 
    Details
    ISSN: 0268-2605
    Keywords: Diorganotin dipeptides ; X-ray structure determination ; 13C ; 119Sn NMR ; IR ; Mössbauer ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dipeptide complexes of the diethyltin(IV) moiety, Et2SnL, have been synthesized, H2L being glycylglycine (H2GlyGly), glycylalanine (H2GlyAla), alanylalanine (H2AlaAla), glycylvaline (H2GlyVal), valylvaline (H2ValVal), glycylmethionine (H2GlyMet), glycyltyrosine (H2GlyTyr). The crystal and molecular structure of the complex Et2SnGlyTyr has been determined by singlecrystal X-ray diffraction. It consists of monomeric units, with the tin atom having a considerably distorted trigonal bipyramidal environment. The dipeptide acts as a tridentate ligand bonding the tin of the C2Sn fragment (equatorial carbon atoms) with the peptide nitrogen atom (equatorial) and axial (monodentate) carboxyl oxygen and amino nitrogen atoms, into a monomeric unit. Bond lengths and angles are reported. Infrared spectroscopic data show the occurrence of monodentate carboxyl in all solid compounds, as well as in methanol solutions of some representative complexes. 119Sn Mössbauer spectroscopic data, and their rationalization through point-charge model (literal version) calculations of the parameter nuclear quadrupole splitting (ΔE) confirm the general occurrence of trigonal bipyramidal structures of the Et2SnGlyTyr type, in the solid state, and give evidence of variations of the C—Sn—C angle in the individual Et2SnL species. Monomers occur in CH3OH solution as suggested by osmometric measurements. 13C and 119Sn NMR spectroscopic data in CD3OD show the persistence of the solid-state structures also in the solution phase, where the order of magnitude of the C—Sn—C angles, as estimated from the coupling constants |1J(119Sn,13C)|, corresponds to that shown by Et2SnGlyTyr in the solid state. 119Sn Mössbauer parameters of Et2SnGlyGly in frozen CH3OH solution are consistent with the assumptions from the NMR studies.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590060110
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of diorganotin(IV) derivatives of 2-mercaptopyridine and crystal structure of diphenyl pyridine-2-thiolatochlorotin(IV) (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 397-407 
    Details
    ISSN: 0268-2605
    Keywords: Organotin ; 2-mercaptopyridine ; pyridine-2-thiolato complexes ; Mössbauer ; IR ; NMR ; crystal structure ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diorganotin(IV) derivatives of 2-mercaptopyridine (HSPy), R2Sn(SPy)2, R2SnCl(SPy) (R = Me, iPr, nBu, tBu, Cy, Ph) and Cy2SnBr(SPy), were obtained from R2SnX2 (X = Cl, Br) and NaSPy.Ph2SnCl(SPy) crystals, as determined by singlecrystal X-ray diffraction, are monoclinic in the space group P21/n. Tin forms with the bidentate SPy ligand a four-membered chelate ring with a short NSnS bite angle of 64.8(1)° leading to a heavily distorted trigonal-bipyramidal environment about tin. Apical Cl-Sn-N angle = 156.1(1)° equatorial C-Sn-C angle = 121.9(2)°. From 119Sn Mössbauer and IR data, analogous structures are inferred for the other solid compounds R2SnX(SPy), and distorted octahedral molecular structures for the solid compounds R2Sn(SPy)2 with R in the trans position, and sulfur atoms and nitrogen-donor atoms each in cis positions. According to IR and 1H, 13C and 119Sn NMR data, the solid-state molecular structures are retained in chloroform solution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080414
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  • 10
    Electronic Resource
    Electronic Resource
    The interaction of organotins with native DNA (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 6 (1992), S. 537-542 
    Details
    ISSN: 0268-2605
    Keywords: Organotin ; DNA ; Mössbauer ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The compounds R2SnCl2 and R3SnCl (R=Me, Et, nBu, nOct, Ph, in ethanol solution) as well as the aqueous species [Me2Sn(OH2)n]2+ and [Me3Sn(OH2)2]+, react with aqueous native DNA, yielding solid phases. According to the pointcharge model treatment of the 119Sn Mössbauer parameter nuclear quadrupole splitting, trans-octahedral R2Sn(O2PXY)2, and trigonalbipyramidal R3Sn(O2PXY), (R=Me, Et, nBu), would occur in the pellets, the tin atoms being coordinated by phosphodiester groups of the nucleic acid. The precipitates from Ph2SnIV would consist of the DNA complex as well as of the Ph2SnIV distannoxane obtained by hydrolysis of the reactant, whilst nOct2SnCl2, nOct3SnCl and Ph3SnCl would mainly yield stannoxanes and hydroxides. The water-soluble hydrolyzed species [Me2Sn(OH)(OH2)n]+, Me2Sn(OH)2 and Me3Sn(OH)(OH2) do not show any interaction with native DNA, although they are possibly coordinated by phosphate oxygen atoms in model aqueous systems, in the presence of excess ligand.These trends have been rationalized by QSAR approach (Quantitative Structure-Activity Relationships) in terms of electronic factors related to tin-oxygen (phosphate) Coulomb interactions, as well as the lipophilicity of R in the RnSnIV moieties.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590060611
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