Vibrational spectrum and structure of dimethylamino-dichloroarsine

The infrared spectra of solid and gaseous dimethylaminodichloroarsine have been recorded from 4000 to 33 cm⁻¹. The Raman spectra of the liquid and solid phases have also been recorded. A comparison of the Raman spectra of the liquid and solid indicates that there is a change in conformational composition between the two phases. The isomer present at room temperature in the liquid and gas phases is assigned to the trans form. A study of the temperature dependence of the intensities of the Raman spectrum indicates that the trans form is converted to a second isomer which is believed to be the gauche isomer as the temperature is decreased. At −190°C, the Raman intensities indicate that the molecule still exists as a mixture of these two isomers. A vibrational assignment is presented and discussed in detail.     

Vibrational spectrum and structure of nitrosothiocarbamylcyanomethanide ion

The IR spectra (400–4000 cm^–1) of the sodium salt of the nonlinear nitrosocontaining acido ligand of a methanide type Na[ONC(CN)C(S)NH₂], as well as of the deutero-derivative compound were studied. The frequencies and the forms of the normal vibrations of NaL (the H-form) and NaL (the D form) were calculated in the harmonic approximation of the valence-force field; a theoretical IR spectrum of compound NaL(H) was obtained from the quantum-chemical calculation. The frequencies observed in the spectrum were assigned from the results of the calculation, the force constants of the bonds were analyzed, and were compared with those for the salt of the oxo anion Na[ONC(CN)C(O)NH₂]. Various Cu²⁺ and Ni²⁺ complexes with a thio ligand were synthesized and the type of coordination of the nonlinear anion was established from the IR spectra.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 3, pp. 312–317. May–June, 1988.     

Vibrational spectrum of 3-methyl and 4-methylpyridine

The assignments of the vibrational spectra of the 3-methyl and 4-methylpyridine molecules have been carried out following the SQMFF methodology (scaled quantum mechanical force field). The theoretical frequencies have been obtained by calculating the RHF/3-21G force field, using the scale factors for pyridine and 2-methylpyridine and are correlated in a satisfactory manner with the frequencies recorded in the IR and Raman of these methyl derivatives.     

Vibrational spectrum and structure of the second stable rotamer of butadiene-1,3

The dependence of the calculated vibrational frequencies of the second stable rotamer of butadiene- 1,3 on the torsional angle about the central single C---C bond has been studied in the interval from 0° (planar syn-form) to 50°. The force field was described by scaled force constants obtained from CNDO/2 calculations. The best agreement between the calculated and experimental vibrational frequencies was found at 25° from the planar syn-form. The results of the vibrational frequency calculations for this configurations of some isotopomers of butadiene- 1,3 are given. In addition, in the light of the theoretical results obtained and new experimental evidence, the assignment of certain out-of-plane normal modes of the anti-form of C₄D₆ is also discussed.     

Vibrational spectrum of cyclic TiC3 in solid Ar

The Fourier transform infrared spectrum of TiC3 was observed by trapping the vapor produced during dual Nd:YAG laser ablation of Ti and C rods in solid Ar at approximately 9 K. Measurements of frequencies and 13C isotopic shifts have enabled the identification of the fanlike (C(2v)) isomer of TiC3 with fundamental vibrations nu3(a1) = 624.3 and nu5(b2) = 1484.2 cm(-1). A third fundamental nu4(b1) has been tentatively identified at 573.8 cm(-1). The results are in good agreement with the predictions of density functional theory calculations at the B3LYP6-311G(3df,3pd) level. The observed C(2v) structure and the observed nu3 metal-carbon stretching mode are also consistent with earlier results from photoelectron spectroscopy.     

Vibrational relaxation of O2(X3 Sigma g-, v = 9-13) by collisions with O2

Vibrationally excited O(2)(X(3) Sigmag(-)) was generated in the UV laser flash photolysis of O(3) and single vibrational level was detected via laser-induced fluorescence (LIF) in the B(3) Sigmau(-)-X(3) Sigmag(-) system. The time-resolved LIF of adjacent vibrational levels has been analyzed by the integrated-profiles method and the rate coefficients for single-quantum relaxation, O(2)(X(3)Sigmag(-), v = 9-13)+ O(2)(v = 0)--> O(2)(X(3)Sigmag(-), v - 1)+ O(2)(v = 1), have been determined. To the best of our knowledge, the rate coefficients for v = 12 and 13 are measured for the first time in the present study. The efficiency of relaxation is higher at lower vibrational levels, indicating that a small energy mismatch is suitable for the energy transfer. The vibrational level dependence of all the rate coefficients for the relaxation measured in the present study and previously reported by several groups can be rationalized by the energy gap law.     

Vibrational spectrum of nitroethylene

Conclusions On the basis of the infrared and Raman spectra of normal and isotope-substituted nitroethylenes, the authors offer an interpretation of the frequencies of nitro-groups conjugated with a multiple C=C bond.Translated from Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 8, pp. 1870–1871, August, 1968.We are grateful to E. F. Ponizovtsev and S. S. Bulakov for their help with the experiments.     

Vibrational spectrum of the tropylium cation

Russian Chemical Bulletin -     

Vibrational relaxation of highly vibrationally excited O3 in collisions with OH

We report a theoretical study of highly excited O3 in collisions with vibrationally cold OH. Special emphasis is placed on initial vibrational energies of O3 between 9 and 21 kcal mol(-1). All calculations have employed the quasiclassical trajectory method and the realistic double many-body expansion potential energy surface for HO 4((2)A). Many aspects of the title relaxation process are presented. The results indicate that it may not be ignorable in studying the stratospheric ozone budget.     

Vibrational spectrum of glycine molecule

The infrared and Raman spectra of glycine molecule has been studied in spectral region 400-4000 cm(-1) in solid form as well as in water. The vibrational frequencies for the fundamental modes of the glycine in neutral and its zwitterionic form have also been calculated using AM1 semiempirical method as well as ab initio method with minimal basis set. The reliability of the minimal basis set and AM1 method with higher basis sets, for IR spectra of the neutral glycine conformers were examined. We find that the 6-21G basis set calculation yields structural parameters, rotational constant and dipole moment of glycine conformers, which are very similar to those obtained from extended basis set calculation as well as experimental values. IR frequencies for glycine conformer I are also calculated in water using SCRF=PCM model and compared with experimental values. A comparison between calculated frequencies for neutral glycine, and its zwitterionic form with observed IR and Raman bands have been made. The total energies for gas phase glycine and its zwitterionic form along with those of hydrated forms were also calculated. It is found from the calculations that in the gas phase neutral glycine is more stable as compared to its zwitterionic form.     

Vibrational spectrum of crystalline cyclopentanone

Infrared and Raman spectra of liquid and solid cyclopentanone have been studied. Spectroscopic evidence shows that the molecule undergoes a solid state phase transition at 168°K. The crystalline form stable below this temperature is ordered and close-packed; its infrared and Raman spectra have been interpreted assuming that cyclopentanone crystallizes in the C⁵_2h or C¹₁ centrosymmetric space groups.     

(H3O)3Sb2Br9: the first member of the M3E2X9 structure family with oxonium cations

(H₃O)₃Sb₂Br₉ [trihydroxonium enneabromidodiantimonate(III)] is the first representative of the M₃E₂X₉ family (M = cation, E = Sb and Bi, and X = Br and I) with oxonium cations. The metastable compound was obtained in trace amounts from a solution of CsBr and SbBr₃ in concentrated aqueous HBr. Single crystals were isolated from the mother liquor and investigated by single‐crystal X‐ray diffraction at 100 K. (H₃O)₃Sb₂Br₉ crystallizes with the Tl₃Bi₂I₉ structure type, which is a distorted defect variant of cubic perovskite. The crystal structure comprises characteristic ²_∞[SbBr₃Br_3/2] double layers of corner‐sharing SbBr₆ octahedra with a [001] stacking direction. Due to the small size of the H₃O⁺ cation and O—H…Br hydrogen bonding, the octahedra are tilted.