Low-temperature reflectance spectra of Rb-TCNQ single crystals

Polarized reflectance spectra were measured on single crystals of Rb-TCNQ (I), Rb-TCNQ (II), and TMB-TCNQ. The near-infrared absorption bands of the two modifications of Rb-TCNQ are shown to be composed of two different electronic excitations. An interpretation is proposed for this phenomenon in terms of the extended Hubbard model.     

Electronic spectra of iodotoluenes

The near u.v. spectra of the vapours of m and p-iodotoluenes are reported. Effects of the substituents on the π → π* bands of benzene are discussed. Solvent effects on the transitions are also reported.     

Electronic spectra of diaminopyridines

The electronic structure and spectra (^* type) of diaminopyridines have been calculated by means of the Pariser-Parr-Pople type calculations, taking into account all the singlet monoexcited configurations. The results are in good agreement with the experiment.Part VII in a series Electronic Structure and Spectra of Organic Molecules of the second author. For Part VI see Kwiatkowski, J. S.: Bull. Acad. polon. Sci, Sér. Sci chim.16, 51 (1968).     

Electronic spectra of nitroethylene

A systematic study of the electronic excited states of nitroethylene (C₂H₃NO₂) was carried out using the approximate coupled‐cluster singles‐and‐doubles approach with the resolution of the identity (RI‐CC2), the time dependent density functional theory with the CAMB3LYP functional (TDDFT/CAMB3LYP) and the DFT multireference configuration interaction (DFT/MRCI) method. Vertical transition energies and optical oscillator strengths were computed for a maximum of 20 singlet transitions. Semiclassical simulations of the ultraviolet (UV) spectra were performed at the RI‐CC2 and DFT/MRCI levels. The main features in the UV spectrum were assigned to a weak n‐π* transition, and two higher energy π_CC+O‐π* bands. These characteristics are common to molecules containing NO₂ groups. Simulated spectra are in good agreement with the experimental spectrum. The energy of the bands in the DFT/MRCI simulation agrees quite well with the experiment, although it overestimates the band intensities. RI‐CC2 produced intensities comparable to the experiment, but the bands were blue shifted. A strong π_CC+O‐π* band, not previously measured, was found in the 8–9 eV range. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Infrared reflectance spectra of some optically biaxial crystals: on the origin of isosbestic-like points in the polarized reflectance spectra

An investigation of the IR polarized reflectance spectra of the orthorhombic K2SO4, KHSO4 and monoclinic CaSO4 x 2H2O, K2Ni(SO4)2 x 6H2O, (NH4)2Ni(SO4)2 x 6H2O was performed in order to explain the appearance of particular intersection points in their spectra. The analogy in the origin of the appearance of intersection points and the well-known isosbestic points in UV-vis and IR spectra was discussed. The reason for such an appearance was identified in the way that the individual reflectances (for radiation polarized along principal dielectric axes) sum up to give the reflectance under arbitrary polarization. This summation may also produce supplementary bands in the reflectance spectra, not predicted by the group theory. It was shown that relatively large LO-TO splitting is needed for the supplementary band(s) to appear, but also the overlapping region must be taken into account.     

Electronic spectra of asym-triazinyl groups

The induction, resonance, and Hammett constants of 3-, 5-, and 6-asym-triazinyl groups were calculated from the data of¹H,¹³C,¹⁹F NMR spectra of isomeric aminophenyl-, hydroxyphenyl-, phenyl-, and fluorophenyl-asym-triazines.Deceased.Translated form Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 257–262, February, 1987.     

Electronic spectra of protonated ferrocenes

The electronic absorption spectra of two protonated ferrocenes have been recorded and the results require a reaccessment of the identity of the species present in weak acid.     

Electronic spectra of ferrocenyl chalcones

The electronic absorption spectra of two series of ferrocenyl chalcones (Fc-CH=CH-CO-Ar,1 andFc-CO-CH=CH-Ar,2) in methanol andn-hexane were recorded. Excellent correlations of _max of the d-d transition between 450–540 nm withHammett substituent constants were found in1, and reasonable correlations in2. In methanol a bathochromic shift of this band occurs. An explanation of this phenomenon, partially based on ligand field calculations, is presented.

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Elektronenabsorptions-Spektren von Ferrocenylchalkonen. Zur Substituentenabhängigkeit von _max des d-d-Überganges

Zusammenfassung Die Elektronenabsorptions-Spektren von zwei Reihen von Ferrocenylchalkonen (Fc-CH=CH-CO-Ar,1 undFc-CO-CH=CH-Ar,2) wurden in Methanol undn-Hexan gemessen. Für1 wurde eine ausgezeichnete Übereinstimmung der _max-Werte des d-d-Überganges (zwischen 450 und 540 nm) mit denHammett-Substituentenkonstanten gefunden, während sie in der Reihe2 befriedigend ist. In Methanol erleidet die genannte Bande eine bathochrome Verschiebung.Eine Erklärung für diese Ergebnisse wird präsentiert, die zum Teil auf Ligandenfeld-Berechnungen basiert.

     

Electronic spectra of Hafner's hydrocarbons

Electronic structures and spectra of Hafner's hydrocarbons have been calculated by means of the semi-empirical SCF CI MO method incorporated with the variable bond-length technique. The results are in good agreement with experimental data.     

Electronic spectra of nitrobenzene derivatives

The gas and solution phase u.v. spectra of some nitrobenzene derivatives with substituents of different electron-donating power were analysed in terms of locally excited states and intramolecular charge transfer configurations in the MIM and PPP approximations. The spectral behaviour of the examined compounds is defined by the different electron-donating power of the substituents and by the degree of mixing of the excited states, following the substitution position.     

Diffuse reflectance spectra of iron(III) vanadates

The electronic spectra of solid iron(III) vanadates FeVO₄ and Fe₂V₄O₁₃ were investigated by the diffuse reflectance technique in the spectral range 12 500–50 000 cm⁻¹. The spectra of investigated vanadates contain 2–3 intensive CT bands in the UV region and two lowest energy d–d bands in the 12 000–22 000 cm⁻¹ range. The presence of the weak bands for FeVO₄ and Fe₂V₄O₁₃ at 16 500 cm⁻¹ and 20 500 cm⁻¹ points to the lattice deffects (oxygen deficiency and the presence of the V⁴⁺ ions) in the structure of investigated vanadates.     

Use of a reflectance attachment to obtain excitation spectra

The feasibility of determining excitation spectra by means of a reflectance attachment for the Beckman DU Spectrophotometer has been demonstrated using aqueous solutions of dichlorofluorescein. Some differential measurements have also been made to explore further the applicability of the technique to analysis.     

Electronic spectra of 2-acetylanthracene

The electronic spectrum of 2-acetylanthracene in a supersonic free jet reveals the existence of two rotational isomers with ≈ 196 cm⁻¹difference between their S₁ origins. In low-temperature rigid glasses, 2-acetylanthracene forms stable dimers. The probable structure of this dimer is also briefly discussed.     

States of cobalt and iron in catalysts supported on TiO2 from data of diffuse reflectance IR spectra of adsorbed carbon monoxide

The variations in the oxidation states of cobalt and iron atoms in pure and mixed Co- and Fe-containing catalysts supported on TiO₂ as a function of the conditions in which the catalysts were prepared and preliminarily treated were studied by analysis of the IR spectra of carbon monoxide adsorbed on these catalysts. A mutual influence of the components was discovered; iron was found to promote reduction of cobalt.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1946–1951, October, 1995.