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  • Biochemistry  (17)
  • crystal structure  (13)
  • Wiley-Blackwell  (30)
  • American Chemical Society
  • American Geophysical Union
  • PANGAEA
  • 1990-1994  (30)
  • 1
    Electronic Resource
    Electronic Resource
    Preparation and crystal structure of the La2Ni12P5 and isotypic ternary lanthanoid - Nickel phosphides (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 587-592 
    Details
    ISSN: 0044-2313
    Keywords: Lanthanoid-nickel phosphides ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Darstellung und Kristallstruktur von La2Ni12P5 und isotypen ternären Lanthanoid-Nickel-PhosphidenDas neue ternäre Phosphid La2Ni12P5 wurde durch Aufschmelzen reiner Komponenten in einem Lichtbogenofen synthetisiert und seine Kristallstruktur durch Einkristalldaten belegt. La2Ni12P5 ist ein erster Vertreter eines neuen Strukturtyps: Raumgruppe P21/m, a = 10,911(3), b = 3,696(2), c = 13,174(4) Å, β = 108,02(2)°, V = 505,2(6) Å3, Z = 2. Die Lageparameter wurden “anisotrop” aus 1 284 Io(hkl) zu RF = 0,0278, RW = 0,0287 (I 〉 3s̰I; 116 Parameter) verfeinert. Charakteristisch für den Aufbau ist die trigonal-prismatische Koordination der Phosphoratome. Die isotypen Phosphide Ln2Ni12P5 (Ln = Ce, Pr, Nd und Eu) wurden ebenfalls dargestellt und durch Pulverdaten charakterisiert.
    Notes: The new ternary phosphide La2Ni12P5 has been prepared by direct arc melting of the components as pure metals and red phosphorus. The crystal structure has been determined using X-ray single crystal diffraction data. The compound exhibits a new type of crystal structure, P21/m with lattice parameters a = 10.911(3), b = 3.696(2), c = 13.174(4) Å, β = 108.02(2)°, V = 505,2(6) Å3, Z = 2. Atomic parameters least squares refinement of 116 independent variables (anisotropic approximation for thermal vibrations) employed 1 284 independent Io(hkl); RF = 0.0278 and RW = 0.0287. The crystal structure is characterized by trigonal prismatic arrangement of phosphorus atoms stacking variant of infinite (with phosphorus centered) columns built by metal trigonal prisms ‖ [010]. Two or three such columns are connected through common edges (lanthanum atoms). The compounds RE2Ni12P5 (where RE = Ce, Pr, Nd and Eu) display the same with La2Ni12P5 crystal structure. Lattice parameters of these compounds have been refined using powder diffraction data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190326
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  • 2
    Electronic Resource
    Electronic Resource
    On the Crystal Structure of LaCaCuGaO5 (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 326-328 
    Details
    ISSN: 0044-2313
    Keywords: Lanthanum calcium copper gallate ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zur Kristallstruktur von LaCaCuGaO5Die Kristallstruktur von LaCaCuGaO5 wurde röntgenographisch an Einkristallen untersucht. Es kristallisiert orthorhombisch in der Raumgruppe C2v22-Ima2 mit a = 15,8467, b = 5,5077, c = 5,3188 Å, Z = 4. LaCaCuGaO5 gehört zum Brownmillerit-Typ und zeigt somit Schichten von eckenverknüpften CuO6-Oktaedern, die über GaO4-Tetraeder vernetzt sind. Die La3+- bzw. Ca2+-Ionen besetzen eine Punktlage statistisch.
    Notes: The crystal structure of LaCaCuGaO5 has been investigated by single crystal X-ray analysis. It crystallizes with orthorhombic symmetry, space group C2v22-Ima2, a = 15.8467, b = 5,5077, c = 5.3188 Å, Z = 4. LaCaCuGaO5 belongs to the mineral Brownmillerite showing layers of corner connected CuO6 octahedra linked by GaO4 tetrahedra. The La3+ and Ca2+ ions are distributed statistically over one crystallographic point position.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200220
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  • 3
    Electronic Resource
    Electronic Resource
    The crystal structure of Bi14I4 condensed bismuth clusters (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 612 (1992), S. 118-122 
    Details
    ISSN: 0044-2313
    Keywords: Bismuth subhalide ; bismuth cluster ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Kristallstruktur von Bi14I4. Kondensierte Bismut-ClusterDie Kristallstruktur von Bi14I4  -  des Endgliedes der bekannten Bismuthalogenide  -  wurde mit röntgenographischen Methoden bestimmt (Einkristall, P21/m, Z = 1, a = 13,309(3) å, b = 11,447 (3) å, c = 4,342 (1) å, γ = 92,08 (3)°, R/Rw = 0,060/0,060 für 369 Reflexe, sinθ/λ ≤ 0,593, MoKα). Die Struktur besteht aus kondensierten Bismut-Clustern und ist aus unendlichen, eindimensionalen Bismut-Netzen aufgebaut, die sich entlang der c-Achse erstrecken und an den Enden Iodatome tragen.Die Besonderheiten der Bismutsubhalogenide, die auch kondensierte Cluster enthalten, werden in bezug auf Bindungslängen und Bindungswinkel besprochen. Die Einwirkung des einsamen Elektronenpaares des Bismutatoms auf die Gestalt der Koordinationspolyeder wird ebenso diskutiert wie der Zusammenhang zwischen der Koordination und der Oxidationsstufe der Bi-Atome.
    Notes: The crystal structure of Bi14I4  -  the final known member of binary bismuth halides  -  was determined by the single crystal X-ray diffractometer technique (P21/m, Z = 1, a = 13.309(3) Å, b = 11.447 (3) å, c = 4.342(1) å, γ = 92.08(3)°, R/Rw = 0.060/0.060 for 369 reflections, sinθ/λ≤ 0.593, MoKγ). The structure consists of condensed bismuth clusters and is build up from infinite one-dimensional bismuth nets running along the c-axis and limited by iodine atoms in another direction.The common structural features of bismuth subhalides containing condensed clusters are also considered based on the analysis of interatomic distances and bond angles. The influence of the lone pair of electrons of the bismuth atom on the geometry of bismuth coordination polyhedra, and the connection between bismuth atoms coordination and the formal oxidation state of these atoms is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926120120
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and Crystal Structure of Hg5Sb2I6 (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 389-392 
    Details
    ISSN: 0044-2313
    Keywords: Mercury antinionide iodide, Hg5Sb2I6 ; Preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Kristallstruktur von Hg5Sb2I6Das Antimonid-Iodid von Quecksilber, Hg5Sb2I6, früher irrtümlich als Hg3Sb2I4 formuliert, wurde in Standardampullen synthetisiert. Einkristalle wurden mittels Transport über die Gasphase erhalten. Hg5Sb2I6: Raumgruppe Pc21n, Gitterparameter: a = 8,108(1), b = 10,702(1), c = 21,295(1) Å. Die Struktur (Einkristall) ist aus [HgSbI3]-Tetraedern und [HgSbI2]-Dreiecken aufgebaut. Alle Antimonatome sind paarweise zu Sb24--Hanteln verbunden. Die Struktur wird mit anderen Strukturen, die Sb24--Hanteln enthalten, verglichen.
    Notes: Mercury antimonide iodide, Hg5Sb2I6, previously and erroneously reported as Hg3Sb2I4 was synthesized using standard ampoule technique. A gas-phase transport reaction was applied for preparation of single crystals. Hg5Sb2I6 crystallizes in the space group Pc21n (No. 33) with unit cell dimensions: a = 8.108(1), b = 10.702(1), c = 21.295(1) Å. Crystal structure solved using single crystal X-ray data is built of [HgSbI3] tetrahedra and [HgSbI2] triangles. All antimony atoms are joined into Sb24- dumbbells. The structure is compared with ones containing similar Sb24- dumbbells.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200232
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic structure and photoelectron spectra of Sb2 and Sb4 from local-spin-density calculations. Model potential for Sb (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 924-929 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry, electronic structure, and photoelectron spectra of Sb2 and Sb4 have been investigated employing the LCGTO-MP-LSD method. For both molecules the geometrical and spectroscopic constants computed using the VWN potential are in very good agreement with the available experimental data. The HeI photoelectron spectra were computed with different potentials (Xα, GL, HL, BH, and VWN). The calculated spectra are in excellent agreement with the experimental ones and the use of the VWN potential gives the most accurate results. The reliable results for molecules complement those for the Sb atom and show that the proposed LSD Model Potential is able to give an accurate description of the structural and spectroscopic properties of the title molecules.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110804
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  • 6
    Electronic Resource
    Electronic Resource
    Minimization and molecular dynamics studies of guanosine and Z-DNA modified by N-2-acetylaminofluorene (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 147-166 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The modeling program AMBER 3.0 was used to study the conformations adopted by the C8-substituted guanosine adduct of the carcinogen N-2-acetylaminofluorene (AAF), called dGuo-AAF. This conformational study was extended to the hexamer d(CGCGCG)2 in the Z form, modified by AAF at guanine G4 with the carcinogen situated at the helix exterior in two different orientations (named ZAAF-5′ and ZAAF-3′). Considering the importance of electrostatic interactions in case of charged molecules like nucleic acids, minimization and molecular dynamics (MD) were performed using different electrostatic parameters (dielectric functions and scale factors). For that purpose, a subroutine allowing the use of a sigmoidal distance-dependent dielectric function εcal has been added to the program. For dGuo-AAF, the results show a great importance of the starting conformation and of the force field parameters on the minimization and MD behaviors. For the AAF-modified Z-DNA, the results display a pronouned dependence on the choice of the set of electrostatic parameters as well. With the distance-dependent dielectric function ε = r, the force field parameters favor the formation of intramolecular H bonds, which can lead to important distortions of Z-DNA. The use of ε = 4r or ε = εcal attenuates effectively such a tendency, except in full MD simulations. The dielectric function εcal is computing intense, but often similar results are obtained with ε = 4r, especially with the use of the BELLY option. AAF appears to prefer the ZAAF-5′ conformation, i.e., with the fluorene ring stacking on the sugar phosphate backbone of the following 5′ C-G bases. Such a conformation is further stabilized by an intramolecular hydrogen bond between the amino group of the 3′ cytosine and the carbonyl group of AAF. The fluorene ring, although mobile around its long axis, does not flip-flop between its two main orientations, ZAAF-5′ and ZAAF-3′. The presence of the AAF does not prevent the ZI to ZII transitions. Whatever the electrostatic parameters, the presence or absence of AAF, the cytosine sugars stay in the C2′-endo pucker domain. In unmodified Z-DNA, the guanine sugars stay in the C3′-endo region, except for the terminal guanines which transit to the C2′endo region. In modified Z-DNA, the sugar of the modified guanine behaves as a terminal guanine sugar.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120203
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  • 7
    Electronic Resource
    Electronic Resource
    MRD-CI potential surfaces using balanced basis sets. VI. Correlation of bond order with bond function composition for first-row diatomic molecules (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 690-696 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: This article presents theoretical calculations on bond energies for the first-row diatomics C2, CN, CO, CF, N2, NO, NF, O2, FO, and F2, which vary in bond order from one to three. The atomic-centered basis functions are systematically augmented with bond functions (BFs), which range in composition from (sp) to 2(spd), to determine the basis set which yields a dissociation energy closest to the experimental De. A strong correlation is found to exist between the bond order and the number of BFs required in the optimum basis set. Based on these results, we are able to predict the optimum composition of the BF basis which should be added to a DZP-quality AO basis set for a case in which only the bond order is known. These optimized BF basis sets are shown in the accompanying article to give more accurate potential curves than larger basis sets without bond functions.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120606
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  • 8
    Electronic Resource
    Electronic Resource
    Effective internal rotation potential energy function of acryloyl fluoride, CH2 = CH — CF =O (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 718-721 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry of acryloyl fluoride was optimized completely at the RHF/6-31G* level of theory at 10 points on the theoretical potential energy curve for internal rotation. The energies obtained were used to determine a six term cosine expansion of the torsional potential energy function. This function was then refined using the experimental torsional transition frequencies in the s-trans and s-cis wells in conjunction with the geometrical parameters optimized at the RHF/6-31G* level. The effective potential function obtained is compared with previous results. The necessity of accounting for relaxation of the geometry upon internal rotation is stressed. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130606
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  • 9
    Electronic Resource
    Electronic Resource
    Transferable semiempirical quadratic force fields: The case of polythiophene and shorter oligomers (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 405-423 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The vibrational spectra of oligomers of thiophene are treated theoretically with the main purpose of deriving information for the interpretation of the infrared and Raman spectra of the polymer and isotopic derivatives. We report the results of a series of semiempirical MNDO calculations on the structure and vibrational properties of oligothiophenes, and we compare the calculated MNDO Pulay scaled force field of the monomer with an empirical harmonic force field that we have obtained by least squares refinement on nine isotopic derivatives. The scaling factors obtained were transferred from thiophene for the computation of the vibrational spectrum and the phonon dispersion curves of the polymer. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540150405
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  • 10
    Electronic Resource
    Electronic Resource
    Microscopic models for quantum mechanical calculations of chemical processes in solutions: LD/AMPAC and SCAAS/AMPAC calculations of solvation energies (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 199-213 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Our previously developed approaches for integrating quantum mechanical molecular orbital methods with microscopic solvent models are refined and examined. These approaches consider the nonlinear solute-solvent coupling in a self-consistent way by incorporating the potential from the solvent dipoles in the solute Hamiltonian, while considering the polarization of the solvent by the potential from the solute charges. The solvent models used include the simplified Langevin Dipoles (LD) model and the much more expensive surface constrained All Atom Solvent (SCAAS) model, which is combined with a free energy pertubation (FEP) approach. Both methods are effectively integrated with the quantum mechanical AMPAC package and can be easily combined with other quantum mechanical programs. The advantages of the present approaches and their earlier versions over macroscopic reaction field models and supermolecular approaches are considered. A LD/MNDO study of solvated organic ions demonstrates that this model can yield reliable solvation energies, provided the quantum mechanical charges are scaled to have similar magnitudes to those obtained by high level ab initio methods. The incorporation of a field-dependent hydrophobic term in the LD free energy makes the present approach capable of evaluating the free energy of transfer of polar molecules from non polar solvents to aqueous solutions. The reliability of the LD approach is examined not only by evaluating a rather standard set of solvation energies of organic ions and polar molecules, but also by considering the stringent test case of sterically hindered hydrophobic ions. In this case, we compare the LD/MNDO solvation energies to the more rigorous FEP/SCAAS/MNDO solvation energies. Both methods are found to give similar results even in this challenging test case. The FEP/SCAAS/AMPAC method is incorporated into the current version of the program ENZYMIX. This option allows one to study chemical reactions in enzymes and in solutions using the MNDO and AM1 approximations. A special procedure that uses the EVB method as a reference potential for SCF MO calculations should help in improving the reliability of such studies.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130212
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