Vibrational and electronic absorption spectra of some trisubstituted benzenes

Despite our studies on the Π* ← Π systems in some trisubstituted benzenes, the available data are limited, especially concerning two heavy and one light or one heavy and two light substituents. We therefore report and interpret the vapour phase electronic absorption, infrared and Raman spectra of 1-bromo-2,4-difluoro-, 1-bromo-3,4-difluoro-, 1-bromo-3,5-difluoro-, 1,3-dichloro-2-fluoro- and 1,3-dichloro-4-fluoro-benzenes.     

Vibrational and electronic spectra of copper(II) chromate

The infrared, Raman and electronic (reflectance) spectra of CuCrO₄ were recorded. The internal vibrations of the CrO²⁻₄ ions were assigned with the aid of a factor group analysis. The ‘d-d’ transitions of the Cu^IIO₆ moieties and one of the O → Cu charge transfer bands could also be assigned. Some comparisons with other structurally related compounds are made.     

Vibrational spectra,force fields and electronic structures of sydnones

Normal vibrational analyses of 3-methylsydnone and 3-methylsydnone-d₄ have been performed. On the basis of the set of force constants obtained, the electronic distribution within the mesoionic ring is evaluated and compared to the results of MO calculations. The π-bond order of the sydnone carbonyl group is shown to be lower than that in alicyclic esters and the unusually high “carbonyl stretching” frequency is due to the contributions from other coordinates to this mode. The splitting of the “carbonyl stretching” band observed in the spectra of 3-methylsydnone and of related derivatives is explained by the strong kinematic coupling between mesoionic bonds.     

Vibrational spectra of mesitylene

Conclusions The Raman spectra of liquid mesitylene and the IR spectra (4000-100 cm^–1) of liquid and gaseous mesitylene were studied. An assignment of the frequencies according to the symmetry and the form of the vibrations is proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2265–2270, October, 1982.     

Vibrational spectra of hexamethylcyclodisilazane

The synthesis and ring cleavage reactions of 2-alkyl-2-trimethylsilylmethyl-1.3-dithianes are described. The cleavage lead to 2-alkylthio-1-vinylsilanes and, via silicon migration, to 2-[3-alkylthio-3-(trimethylsilyl)propylthio]-1-alkenes.     

Vibrational spectra of isocyanocyclopropane

Infra-red spectra of isocyanocyclopropane have been measured from 4000 to 400 cm⁻¹ in the vapour and to 200 cm⁻¹ in the liquid phase. The Raman spectrum of the liquid was obtained from 4000 to 50 cm⁻¹. A vibrational assignment of all fundamentals is proposed, which is in accord with those of structurally related molecules. Comparison with the vibrational spectra of cyanocyclopropane and cyclopropylacetylene shows the presence of a sizeable inductive effect of the nitrogen atom in isocyanocyclopropane.     

Vibrational spectra of diethylsulfoxide

FT IR and Raman spectroscopic studies of pure diethylsulfoxide (DESO) in the liquid and in the solid states and its solutions in various solvents have been performed. Analysis of SO- and CH-stretching regions in a wide range of concentration shows that the bands may be fitted satisfactorily by considering seven components. In addition, fundamental frequencies have been assigned using ab initio calculations at the RHF/3-21G* levels. The results obtained confirm a viewpoint on a self-associative structure of DESO, and support the hypothesis of the existence of different types of intermolecular associates including both dipole-dipole and hydrogen bonding mechanisms.     

Vibrational analysis of the Raman,infrared and electronic spectra of hexafluoromanganate(IV)

From the Raman, infrared and electronic spectra all of the fundamental vibrational frequencies were determined for both the ground state⁴ A _2g and the excited² E _g In addition some fundamental frequencies were established for the⁴ T _2g and⁴ T _1g excited states from low temperature absorption spectra.

---

Zusammenfassung Aus den Raman-, Infrarot- und Elektronenspektren wurden alle Grundschwingungsfrequenzen für den Grundzustand⁴ A _2g und den angeregten² E _g-Zustand bestimmt. Ferner wurden noch einige der entsprechenden Größen für die angeregten Zustände⁴ T _2g und⁴ T _1g aus Tieftemperatur-Absorptionsspektren ermittelt.

---

Résumé Toutes les fréquences fondamentales de vibration ont été déterminées pour l'état fondamental⁴ A _2g et l'état excité² E _g à partir des spectres Raman, infra-rouge et électronique. De plus, certaines fréquences fondamentales des états excités⁴ T _2g et⁴ T _1g ont été obtenues à partir des spectres d'absorption à basse température.

---

---

Dedicated to the memory of Prof. Hans-Ludwig Schläfer.     

Vibrational spectra of polyacetylenes

A considerable amount of information about optical and electronic properties of polyacetylenes has been obtained during the last decade from vibrational spectroscopy. In this lecture several basic points not yet fully understood will be discussed and a new method for evaluating the vibrational density of states for random defects will be presented.     

Vibrational spectra of dipropylsulfoxide

FTIR and Raman spectra analysis of pure dipropylsulfoxide (DPSO), binary mixtures of DPSO/CCl(4), and DPSO/water has been first performed. The complex pattern of spectra has been explained on the basis of molecular interactions between DPSO and other molecules and, in the aqueous solutions, the role of both hydrophilic and hydrophobic interactions have been discussed depending on the concentrations. The changes in the intensities and in the frequencies of DPSO bands on concentration have been considered. The curve fitting procedure has been performed for both SO and C-H stretching region, and, on the basis of deconvolution results different type of molecular interactions have been considered. Density function theory DFT/(B3LYP) method has been used to determine the optimized geometry for free DPSO and for 1 DPSO:1 water complex. On the basis of the 6-31+G(d) quality sets parameters, the DFT calculated bond parameters and harmonic vibrations are in a very good agreement with experimental data.     

Vibrational spectra of indole

Polarized i.r. spectra of partially oriented indole crystals grown from the melt between pressed salt plates and the Raman spectra of the melt and polycrystalline indole are reported. Some fundamental vibrational assignments and the manifestations of the NH ⋯ π interaction in the vibrational spectra are discussed.     

Vibrational spectra of the excited electronic state of rhodamine molecules obtained by cars spectroscopy

CARS spectra of the ground and an excited electronic state of rhodamine dyes are observed under two different resonance conditions using nanosecond dye lasers The observed differences are not due to structural changes.     

Vibrational spectra and structure of trinitromethane

The vibrational spectrum of trinitromethane was interpreted in terms of the additive interatomic interaction model on the basis of experimental infrared and Raman spectra of HC(NO₂)₃, DC(NO₂)₃, HC(¹⁵NO₂)₃ and normal coordinate analysis. The frequency assignment results were used in discussing its structure. It was shown that the symmetry of trinitromethane is below C₃ in the liquid state.     

Vibrational spectra of mesidine and mesitol

The i.r. and Raman spectra of 2,4,6-trimethylaniline (mesidine) and 2,4,6-trimethylphenol (mesitol) have been measured in solutions and as solids and the observed frequencies assigned to various normal modes. The barriers to internal rotation of the NH₂ group about the CN bond in mesidine and the OH group about the CO bond in mesitol were found to be 18.6 and 15.6 kJ mol⁻¹, respectively. By comparison with unsubstituted aniline and phenol, these values suggest an increase in double-bond character of the CN and CO bonds which most likely arises from an inductive interaction of the methyl groups with the aromatic rings.