Infrared and polarized raman spectra of kainite

The i.r. and Raman spectra of KMgClSO₄·3H₂O and its deuterated compound KMgClSO₄·3D₂O have been recorded and analysed. Due to site symmetry effects the i.r. inactive modes appear as sharp bands in the i.r. spectrum. Water bands indicate strong hydrogen bonding and show the presence of three crystallographically distinct water molecules in the unit cell.     

Infrared and Raman spectra of N-n-alkylthioureas

The i.r. and Raman spectra of solid alkyl thioureas H₂NCSNH(CH₂)nCH₃ (n = 0–15), TUR′, and their urea analogue H₂NCONH(CH₂)nCH₃ (n = 0–9), UR′, are presented. The vibrational properties of N-monosubstituted TUR′and UR′are studied on the basis of the spectral comparison between the members of the series and compared with the properties of N,N′-di-substituted MTUR′ and MUR′, correspondingly. Some features of the methylene ν₄ and ν₇ band progressions were found to shift from the corresponding features of solid n-alkanes by vibrational coupling. The observed wavenumber of the longitudinal accordion-like skeletal motion (LAM-1) of TUR′ was found to correspond to that of the n-alkane with the same number of carbon atoms as TUR′ has skeletal atoms.     

Infrared and Raman spectra of pyromellitic dithioanhydride

The i.r. spectrum of pyromellitic dithioanhydride has been measured from 4000 to 200 cm⁻¹; polarized i.r. spectra of single crystals have been also obtained. The Raman spectra of polycrystalline samples and solutions have been recorded and polarization of many lines has been determined. A detailed assignment of most of the fundamentals has been proposed on the basis of i.r. dichroism of the single crystals, Raman spectra and analogies with the spectra of related molecules.     

Infrared and Raman spectra of 2,4-dimethylaniline

The infrared spectra of 2,4 dimethylaniline have been recorded in the region 3600-100 cm⁻¹. The Raman spectra with polarization measurements have been recorded and investigated for the first time in the region 3500-100 cm⁻¹. New frequency assignments have been proposed assuming the molecule to possess an approximateC ₂ symmetry. Fifty normal modes of the molecule, out of a possible fifty four modes, have actually been observed and assigned including twenty seven hitherto unreported frequencies. The observed spectral changes give evidence of the presence of an intermolecular hydrogen bonding of an N−H...N type, and suggest a solid-solid phase transition between 223 and 123 K in the molecule.     

IR and polarized Raman spectra of strontium tartrate trihydrate

The IR and polarized Raman spectra of SrC₄H₄O₆ · 3H₂O have been recorded and analysed. The factor group analysis of the divalent tartrate ion has been carried out on the basis of C₂ symmetry. As the ion possesses lower symmetry in the crystal, splittings have been observed for the different vibrational modes. Separate bands in the bending region of water suggest the existence of three crystallographically different water molecules in the crystal, which is confirmed by deuterium substitution.     

Raman and polarized infrared spectra of pyridine-2-thione

Polarized i.r. spectra of oriented polycrystals and the i.r. and Raman spectra of polycrystalline samples of pyridine-2-thione have been obtained. The Raman spectra of a solution of pyridine-2-thione has also been measured and the polarization of many lines determined. The i.r. spectra of S-methyl and N-deuterated compounds have also been investigated. A complete assignment of all the observed peaks has been possible. The results are correlated with the assignments available for related systems.     

Infrared and Raman spectra of phthalimide and isatin

The i.r. spectra of phthalimide and isatin have been measured from 4000 to 200 cm⁻¹; polarized i.r. spectra of oriented single crystals have been also obtained. The Raman spectra of polycrystalline samples and solutions have been measured and polarization of many lines has been determined. A detailed assignment of most of the observed frequencies has been proposed on the basis of dichroism of the single crystals, Raman spectra and analogies with the spectra of related molecules.     

The polarized infrared and Raman spectra of crystalline ammonium trifluoromethanesulphonate

The infrared and Raman spectra of NH₄CF₃SO₃ were obtained and analysed and an assignment was proposed for the observed bands. The assignment of some anion bands was supported by means of the polarized spectra of monocrystals. The fundamental frequencies of the anion were used for a normal coordinate calculation.     

Infrared and Raman spectra of cytosine and cytidinium salts

Studies of the infrared and Raman spectra of cytidinium salts are presented. They are supplemented by the measurements of the infrared spectra of the c     

Infrared and Raman spectra of quinolinic thioanhydride and N-methyl-quinolinimide

The i.r. spectra of quinolinic thioanhydride and N-methyl-quinolinimide have been obtained from 4000 to 200 cm⁻¹; polarized spectra of oriented samples have been also obtained. The Raman spectra of polycrystalline samples and solutions have been measured and polarization of many lines has been determined. A detailed assignment of most of the observed frequencies has been proposed based upon dichroism of the oriented samples, Raman polarization data and analogies with the spectra of related molecules.     

Infrared and Raman spectra of octa(hydridosilasesquioxanes)

We report the NIR FT-Raman spectrum of H₈Si₈O₁₂ and the fundamental IR modes of D₈Si₈O₁₂. The fundamental modes are assigned according to a normal coordinate analysis and in terms of internal vibrations.     

Raman spectra of ionic liquids: a simulation study of AlF3 and its mixtures with NaF

Theoretical Raman spectra of the melts of NaF/AlF3 mixtures have been obtained from computer simulations in order to examine how the Raman spectra reflect the coordination structure around the Al3+ ions. The Raman spectra, both polarized and depolarized, are calculated from a model for the dependence of the polarizability of the system on the ionic coordinates which was inspired by electronic structure calculations of the polarizabilities of ions in a condensed-phase environment. The shapes of the spectra and their evolution with composition in the mixtures conform remarkably well to those seen experimentally, and we discuss the relationship between the bands seen in the spectra and the vibrational modes of the AlFn(3-n) coordination complexes which are found in the melts. Finally, we calculate quantities which relate to the degree of cross-linking between these coordination complexes and their lifetimes.     

Infrared and Raman spectra of 8-azaguanine and 8-azaadenine

The IR and Raman spectra of 8-azaguanine and 8-azaadenine have been studied. The spectra of 8AG have been critically examined and compared with those of guanine and 9-methylguanine. Similarly, the spectra of 8-azaadenine have been examined and compared with those of adenine and 9-methyladenine. It has been possible to refute or accept the assignments for certain frequencies proposed earlier in the parent molecules by other workers, and thus almost unambiguous assignments for several frequencies in guanine and adenine as well as in 8AG and 8AA have been obtained. Several frequencies have been explained as combinations involving a 130 cm⁻¹ vibration which has been assigned to the ring-folding mode. It is found that not as many combination bands involving this mode occur in 8AA as those in 8AG. These observations indicate that guanine and 8AG are geometrically more flexible than adenine and 8AA.     

Infrared and Raman spectra and normal coordinate analysis of disilylchloride

Disilylchloride has been synthesized by chlorination of disilane with boron trichloride. FTIR spectra have been obtained of the vapour phase and Raman spectra of the liquid phase of this molecule. The spectra are fully assigned for the first time. A normal coordinate analysis is carried out and the refined force constants are compared to previous works on disilane, disilyliodide and silylchloride. The height of the potential energy barrier to internal rotation in disilylchloride is also evaluated.     

Infrared and Raman spectra of alkali metal salts of TCNQ

The infrared and Raman spectra of the series of alkali metal salts of the monoanion radical of tetracyanoquinodimethane MTCNQ (M = Li, Na and K) are observed and analysed both in the low-frequency lattice vibration region and in the intramolecular vibration region. The vibrational assignments are made, by comparing the spectra of MTCNQ with one another and investigating the difference between the powder and solution spectra and the temperature dependence of the spectra. The monomer—dimer phase transition in NaTCNQ and KTCNQ of the columnar stacking of TCNQ⁻ does not cause a marked change in the low-frequency spectra due to the lattice vibrations. The vibronically activated bands of the totally symmetric modes of the TCNQ⁻ anion are observed in the infrared spectra, which are associated with the charge-transfer intermolecular interaction. A lattice dynamical analysis for the optically active crystal vibrations of NaTCNQ and KTCNQ is performed, and the result of this calculation also verifies the vibrational assignments of the low-frequency infrared and Raman bands attributed experimentally to the translational and rotational lattice modes.     

Infrared and Raman spectra of crystalline para-bromoaniline at low temperatures

The polarization characteristics of the i.r. absorption bands of oriented p-bromoaniline crystal films have been studied at low temperatures. Raman spectra of this compound in solution and in the polycrystalline state have been recorded as an aid to the vibrational assignment of the crystal bands. The vibrational spectra are interpreted to deduce the crystal factor group (D_2h) and the molecular site symmetry (C_s). The observed factor group splittings and dichroic ratios suggest the crystal unit cell of p-bromoaniline to be isostructural with that of p-chloroaniline.     

Infrared and Raman spectra and normal coordinate calculations for methylisothiocyanate

The infrared spectra (3200-50 cm^?1) of gaseous and solid CH₃NCS and CD₃NCS and the Raman spectra (3200-10 cm^?1) of the liquids and solids have been recorded. The spectra have been interpreted on the basis of a “pseudo-symmetric top” with C_3v symmetry. An assignment of the fundamental vibrations in both molecules, based on their infrared band contours, depolarization values and group frequencies, is given and discussed. Particularly interesting is the low-frequency region where band maxima were observed at 152 and 80 cm^?1 for CH₃NCS and 139 and 71 cm^?1 for CD₃NCS in the infrared spectra of the gases. A normal coordinate analysis has also been carried out based on C_3v symmetry. Considerable mixing was found between the C_αN stretch and NCS symmetric stretch in both isotopic species. The other normal modes in CH₃NCS are reasonably pure but, for the CD₃NCS molecule, considerable mixing was found between the CD₃ stretches and NCS antisymmetric stretch. The proposed vibrational assignment and the results of the normal coordinate calculations are discussed and compared with the results obtained for similar molecules.     

Infrared and Raman spectra of phtalic,isophtalic and terephtalic acids

The i.r. spectra of phtalic, isophtalic and terephtalic acids as KBr pellets as well as Raman spectra of microcrystalline powder have been investigated. Most vibrations have been assigned by correlation with the spectra of the previously studied phtalate, isophtalate and terephtalate ions. The COOH characteristic vibrations have been assigned as vibrations of the hydrogen-bonded centrosymmetric “dimers” COOH … HOOC, and a general assignment is proposed for combination bands in the range 3000-2500 cm⁻¹.