Hydrogen Bond Lengths (hydrogen + bond_length)

Distribution by Scientific Domains


Selected Abstracts


Raman spectroscopy of walpurgite

JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2006
Ray L. Frost
Abstract Raman spectra of walpurgite, (UO2)Bi4O4 (AsO4)22H2O, recorded at 298 K and 77 K are presented and compared with infrared spectra of walpurgite and phosphowalpurgite. Bands connected with (UO2)2+, (AsO4)3,, and H2O stretch and bend, and BiO stretch are tentatively assigned. Hydrogen bond lengths are calculated from the wavenumbers of the H2O stretching vibrations and compared with those from the crystal structure analysis of walpurgite. Copyright 2005 John Wiley & Sons, Ltd. [source]


Study of peptide conformation in terms of the ABEEM/MM method

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2006
Zhong-Zhi Yang
Abstract The ABEEM/MM model (atom-bond electronegativity equalization method fused into molecular mechanics) is applied to study of the polypeptide conformations. The Lennard,Jones and torsional parameters were optimized to be consistent with the ABEEM/MM fluctuating charge electrostatic potential. The hydrogen bond was specially treated with an electrostatic fitting function. Molecular dipole moments, dimerization energies, and hydrogen bond lengths of complexes are reasonably achieved by our model, compared to ab initio results. The ABEEM/MM fluctuating charge model reproduces both the peptide conformational energies and structures with satisfactory accuracy with low computer cost. The transferability is tested by applying the parameters of our model to the tetrapeptide of alanine and another four dipeptides. The overall RMS deviations in conformational energies and key dihedral angles for four di- or tetrapeptide, is 0.39 kcal/mol and 7.7. The current results agree well with those by the accurate ab initio method, and are comparable to those from the best existing force fields. The results make us believe that our fluctuating charge model can obtain more promising results in protein and macromolecular modeling with good accuracy but less computer cost. 2005 Wiley Periodicals, Inc. J Comput Chem 27: 1,10, 2006 [source]


Raman microscopy of the mixite mineral BiCu6(AsO4)3(OH)63H2O from the Czech Republic

JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2010
Ray L. Frost
Abstract Raman microscopy of the mixite mineral BiCu6(AsO4)3(OH)63H2O from Jchymov and from Smrkovec (both Czech Republic) has been used to study their molecular structure. The presence of (AsO4)3,, (AsO3OH)2,, (PO4)3, and (PO3OH)2, units, as well as molecular water and hydroxyl ions, was inferred. OHO hydrogen bond lengths were calculated from the Raman and infrared spectra using Libowitzky's empirical relation. Small differences in the Raman spectra between both samples were observed and attributed to compositional and hydrogen-bonding network differences. Copyright 2009 John Wiley & Sons, Ltd. [source]


Raman spectroscopic study of the uranyl mineral pseudojohannite Cu6.5[(UO2)4O4(SO4)2]2(OH)525H2O

JOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009
Ray L. Frost
Abstract Raman spectra of pseudojohannite were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (SO4)2, units and of water molecules. The published formula of pseudojohannite is Cu6.5(UO2)8[O8](OH)5[(SO4)4]25H2O. Raman bands at 805 and 810 cm,1 are assigned to (UO2)2+ stretching modes. The Raman bands at 1017 and 1100 cm,1 are assigned to the (SO4)2, symmetric and antisymmetric stretching vibrations. The three Raman bands at 423, 465 and 496 cm,1 are assigned to the (SO4)2,,2 bending modes. The bands at 210 and 279 cm,1 are assigned to the doubly degenerate ,2 bending vibration of the (UO2)2+ units. UO bond lengths in uranyl and OHO hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright 2009 John Wiley & Sons, Ltd. [source]


Raman spectroscopic study of the mineral guilleminite Ba(UO2)3(SeO3)2(OH)43H2O

JOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2009
Ray L. Frost
Abstract The Raman spectrum of the mineral guilleminite Ba[(UO2)3O2(SeO3)2](H2O)3 was studied and complemented by the infrared spectrum of this mineral. Both spectra were interpreted and compared with the spectra of marthozite, larisaite, haynesite and piretite, all of which should have the same phosphuranylite anion sheet topology. The presence of symmetrically distinct water molecules and hydrogen bonds was inferred from the spectra. This is in agreement with the crystal structural analysis of guilleminite. UO bond lengths in uranyl and OHO hydrogen bond lengths were calculated from the Raman and/or infrared spectra of guilleminite. Copyright 2008 John Wiley & Sons, Ltd. [source]


Raman spectroscopic study of the uranyl selenite mineral marthozite Cu[(UO2)3(SeO3)2O2]8H2O

JOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2008
Ray L. Frost
Abstract The mineral marthozite, a uranyl selenite, has been characterised by Raman spectroscopy at 298 K. The bands at 812 and 797 cm,1 were assigned to the symmetric stretching modes of the (UO2)2+ and (SeO3)2, units, respectively. These values gave the calculated UO bond lengths in uranyl of 1.799 and/or 1.814 . Average UO bond length in uranyl is 1.795 , inferred from the X-ray single crystal structure analysis of marthozite by Cooper and Hawthorne. The broad band at 869 cm,1 was assigned to the ,3 antisymmetric stretching mode of the (UO2)2+ (calculated UO bond length 1.808 ). The band at 739 cm,1 was attributed to the ,3 antisymmetric stretching vibration of the (SeO3)2, units. The ,4 and the ,2 vibrational modes of the (SeO3)2, units were observed at 424 and 473 cm,1. Bands observed at 257, and 199 and 139 cm,1 were assigned to OUO bending vibrations and lattice vibrations, respectively. OHO hydrogen bond lengths were inferred using Libowiztky's empirical relation. The infrared spectrum of marthozite was studied for complementation. Copyright 2008 John Wiley & Sons, Ltd. [source]


Gaseous HgH2, CdH2, and ZnH2

CHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2005
Alireza Shayesteh
Abstract Gaseous HgH2, CdH2, and ZnH2 molecules were synthesized by the direct gas-phase reaction of excited mercury, cadmium, and zinc atoms with molecular hydrogen. The molecules were identified by their high-resolution infrared emission spectra, and the metal,hydrogen bond lengths were determined from the rotational analysis of the antisymmetric stretching fundamental bands. [source]