Vibrational assignments and electronic structure calculations for 6‐thioguanine

The Fourier transform Raman and Fourier transform infrared (FT‐IR) spectra of thioguanine have been recorded. Ab initio and density functional computations of the vibrational (IR) spectrum, the molecular geometry, Highest Occupied Molecular Orbital (HOMO)–Lowest Unoccupied Molecular Orbital (LUMO) energy gaps and polarizabilities were studied. On the basis of the comparison between calculated and experimental results and the comparison with related molecules, assignments of fundamental vibrational modes are examined. The observed and simulated spectra were found to be well comparable. The electronic transition energies and intensities of spectral lines were carried out using TDDFT and ZINDO methods. Copyright © 2009 John Wiley & Sons, Ltd.     

Infrared and Raman spectra and vibrational assignments of diiodomethane and its deuterated analogs

The infrared (from 4000 to 100 cm^?1) and Raman spectra of CH₂I₂ and CD₂I₂ have been recorded in the liquid and gaseous phases. Assignments have been made for all observed bands and, in the case of CH₂I₂, compared with those previously reported. Some bands appearing in the CD₂I₂ spectrum have been attributed to the presence of CHDI₂. The wavenumbers of the fundamental bands of CHDI₂ have been calculated from those of CH₂I₂ and CD₂I₂ using Brodersen and Langseth's rule, and compared with those observed in the CD₂I₂ spectrum.     

Vibrational spectra and assignments for phenazine

Assignments of 56 of the 60 fundamental vibrations of phenazine are reported. Assignments were made from infrared and Raman spectra, comparison to the vibrational assignments of anthracene, and the results of a normal coordinate calculation of the fundamentals.     

A modified Urey-Bradley force field for 2-chloropropane and its deuterated derivatives

A modified Urey-Bradley field has been developed for 2-chloropropane by a least-squares fit of the normal frequencies of this compound and two of its deuterated derivatives. Using this force field, the normal modes of 2-chloropropane and three of its deuterated derivatives have been calculated. This work is part of a study of the applicability of the Urey-Bradley field to the vibrations of chlorine-substituted hydrocarbons.     

Methanol and deuterated species: Infrared data,valence force field,rotamers, and conformation

New infrared measurements of gaseous and matrix-isolated methanol and 7 deuterated species are presented and analyzed. A revised assignment for the species CH₃OH(D) and CD₃OH(D) is used to determine 15 significant parameters of a valence force field by a converged simultaneous least-squares adjustment to 44 observed fundamentals. The respective frequencies calculated for the rotamers of CH₂DOH(D) and CHD₂OH(D) turn out to be a valid prediction as they are used to assign 78 observed fundamentals of the species with partially deuterated methyl groups. The values of the 15 force constant parameters are refined by including all 122 observed fundamentals. The force field contains significant deviations from local C_3v symmetry of the methyl group. Such an asymmetry, in the CH-stretching diagonal part, produces a difference of about 10 cm^?1 in the zero point energy of symmetric and asymmetric rotamers of the species with partially deuterated methyl groups. Calculations based on equilibrium structures with and without methyl tilt yield better agreement with observed data in the nontilted case. A preliminary calculation of relative intensities reproduces the major effects of isotopic substitution and rotational isomerism. Experimental evidence for the staggered conformation is obtained from a comparison of observed data with calculated results based on staggered and eclipsed models.     

Vibrational spectrum and assignments for 1,6- and 1,8-naphthyridine

Assignments of all 42 fundamental vibrations of 1,6- and 1,8-naphthyridine are reported. Assignments were made from infrared and Raman spectra, comparison with naphthalene and related azanaphthalenes, and the results of a normal coordinate calculation of the fundamentals.     

Quantum-chemical modeling of ferroelectric solids with hydrogen-bond networks of different dimensionalities and their deuterated analogs

The application of quantum chemistry methods in the microscopic theory of H/D-bonded ferroelectrics and antiferroelectrics is illustrated using a comparative analysis of low-temperature order-disorder structural phase transitions in zero-dimensional materials of the K₃H(SO₄)₂ family, zero-dimensional crystals of 5-halo derivatives of 9-hydroxyphenalenone (5Hal-9HPO), and three-dimensional crystals of potassium dihydrogen phosphate (KDP) and potassium dideuterium phosphate (DKDP) as examples. In the framework of the Ising model with tunneling, it is demonstrated that (in agreement with experimental data) the transition to the low-temperature ordered phase in zero-dimensional materials is possible only in the case of their deuteration, whereas the quantum paraelectric behavior is characteristic of undeuterated samples. This behavior for KDP crystals is impossible due to the sharp increase in the Ising parameters as compared to zero-dimensional materials. The factors responsible for the increase in these parameters are considered.     

Vibrational spectrum of HCCl3 and the force field of chloroform

From high resolution infrared absorption studies in the gaseous phase, the fundamental vibrational frequencies and some overtone and combination bands of H¹³CCl₃ have been determined. The infrared spectrum of H¹²CCl₃ has been reinvestigated with higher resolution in order to get accurate ¹²C/¹³C isotope frequency shifts. These shifts in conjunction with ³⁵Cl/³⁷Cl frequency shift data for H¹²CCl₃, H¹³CCl₃, D¹²CCl₃, and the centrifugal distortion constants of H¹²CCl₃ are used to determine the general valence force field, which reproduces all data within the error limits.     

Intramolecular coupling of vibrational modes and the assignments of the partially deuterated dihalogenomethanes, -silanes, and -germanes

The fundamental vibrational wavenumbers of seven molecules of the type MHDX₂ (where M = C, Si, Ge and X = F, Cl, Br) have been calculated from those of the corresponding species MH₂X₂ and MD₂X₂, using the complete isotopic rule of Brodersen and Langseth. These wave-numbers have been used to test the force fields previously computed for the MH₂X₂ and MD₂X₂ molecules. The potential energy distributions calculated for the MHDX₂ species have been employed as aids in clarifying the assignments of their vibrational spectra.     

Spectroscopic investigation of compounds with P-H bond. Vibrational spectra,force field,and conformation of dimethyl phosphite molecules

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 6, pp. 944–950, December, 1989.     

Vibrational spectroscopy of trans and cis deuterated formic acid (HCOOD): Anharmonic calculations and experiments in argon and neon matrices

The absorption spectra of trans and cis conformers of deuterated formic acid (HCOOD) isolated in argon and neon matrices are analyzed in the mid-infrared and near-infrared spectral regions (7900-450 cm⁻¹). Vibrational excitation by narrow-band IR radiation is used to convert the lower-energy trans conformer to the higher-energy cis form. A large number of overtone and combination bands are identified. The results of anharmonic vibrational calculations (CC-VSCF) for both conformers are reported and compared to the experimental spectra.     

Vibrational properties of thymine,uracil and their isotopomers

Density functional theory (DFT) calculations using the B3LYP/6‐311G(d,p) basis set of ten isotopomers of thymine and four isotopomers of uracil, including the natural abundance isotopomers, are reported. Comparison of the calculated wavenumber shifts upon hydrogen, carbon and nitrogen isotopic substitution with those from experimental Raman and infrared measurements show good agreement in both the direction and the magnitude of the shift. These results are contrasted to previously reported calculations and discussed in the context of assigning the normal modes of thymine and uracil. Copyright © 2007 John Wiley & Sons, Ltd.     

Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds,and crystal structure of KCuBr3

Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching Cu^II X modes in the equatorial plane, were found in the ranges 247–288 cm⁻¹ for X = Cl, and 173–189 cm⁻¹ for X = Br, while the low‐wavenumber stretching modes for the weaker axial Cu X interactions varied considerably. The tetrahedral coordination for Cs₂CuCl₄ and Cs₂CuBr₄ leads to somewhat lower Cu X symmetric stretching wavenumbers, 295 and 173 cm⁻¹, respectively. The assignments of the copper–ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged Cu X stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn–Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer‐sphere cations. Force constant ratios for terminal and bridging metal–halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M₂X₆ species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr₃ (K₂Cu₂Br₆), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu₂Br₆]²⁻ complexes held together by weak axial Cu Br interactions. Copyright © 2007 John Wiley & Sons, Ltd.     

Vibrational assignments for styrene-β-D2 from the infrared and Raman spectra

The molecule styrene-β-D₂ has been prepared. The liquid-phase infrared spectrum in the region 400 to 3500 cm^?1 and the laser Raman spectrum have been recorded. Vibrational assignments for this molecule have been made largely by comparison with those of Condirston and Laposa (2) for C₆H₅CHCH₂, C₆H₅CDCD₂, C₆D₅CHCH₂, and C₆D₅CDCD₂.     

静电系统受力和力矩计算

具有终端的静设备系统,是一种把电能转移为机械能的换能器。根据能量守恒和转换定律,导出该静电系统受力和力矩的两种计算方法及应用实例。