Electronic absorption spectra of 5- and 6- fluoroindoles

The electronic absorption spectra of 5-and 6-fluoroindoles, corresponding to the λ2850 Å system of indole, have been recorded in the vapour phase and analysed, assuming C_s symmetry for the molecules. The observed band system in both the molecules which lies in the region λ3100–2680 Å has been identified as a π* ← π transition corresponding to a ¹A′ ← ¹A′ transition. The i.r. spectra of these molecules have also been recorded and analysed and the results are used in the analyses of the electronic spectra. These show that there is not much change in the shape and very little change in size of either of these molecules in the excited electronic states.     

The near ultraviolet absorption spectra of 2,3-, 2,4- and 2,5-dimethylbenzonitriles

A new technique—photoacoustic spectroscopy (PAS—was applied for the study of the electronic transitions in three isomers, 2,3-, 2,4- and 2,5-dimethylbenzonitriles. The PAS spectra were compared with solution and vapour phase spectra. A probable detection of S → T absorption in the molecules is considered to be of significance in the present investigation. It is also shown that two π → π* transitions analogous to the benzene strong 200 nm and weak and forbidden 260 nm transitions could be identified in all three molecules. An interesting feature is regarding the identification of a few combination bands in the excited state of an electronic transition which could be fairly comparable with such combinations observed in the near i.r. PAS spectra of the molecules, in the ground state.     

Triplet-triplet absorption spectra of meso-tetraphenyl-2,3-tetranaphtho-2,3-tetraphenanthroporphins

Flash photolysis has been used to measure triplet-triplet (T-T) absorption spectra of meso-tetrapheny1-2,3-tetranaphthorphin and its zinc complex, and also zinc complexes of two isomers of meso-tetrapheny1-2,3-tetraphenanthrenopurphin. An analysis has been made of the inf Iuence of structural changes on the T-T absorption spectra.Institute of Physics, Academy of Sciences of the Belorussian SSR, Minsk. Scientific-Research Institute of Organic Intermediates and Dyestuffs, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 1, pp. 105–108, January–February, 1991. Original article submitted February 24, 1989.     

Electronic absorption spectra and kinetics of the photochemical conversions of 2,3-dihydroxymethylquinoxaline 1,4-di-N-oxide in solutions

Conclusions The electronic absorption spectra of 2,3-dihydroxymethylquinoxaline 1,4-di-N-oxide (di-oxidine) in water, ethanol, and chloroform have been measured; the kinetics have been studied; and the absolute quantum yields of the photochemical decomposition of dioxidine in the solutions have been determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 806–810, April, 1986.     

Electronic structure and absorption spectra of indolizines

The electronic structure and spectra of indolizine and a large number of its aza-derivatives have been calculated by the SCFMO-CI method, taking into account all the singlet monoexcited configurations. The results are in good agreement with the experiment. The assignment of the observed bands is also discussed.

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Zusammenfassung Mit dem SCFMO-CI-Verfahren werden Elektronenstruktur und Spektren des Indolizins und mehrerer seiner Derivate berechnet, wobei alle einzeln angeregten Singulett-Konfigurationen berücksichtigt werden. Die Ergebnisse stehen in ausgezeichneter Übereinstimmung mit dem Experiment. Die Zuordnung der beobachteten Banden wird diskutiert.

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Résumé La structure et les spectres électroniques de l'indolizine et de plusieurs ses aza-dérivés ont été calculés par la méthode SCFMO-CI, en considérant toutes les configurations singulets monoexcitées. Les résultats sont en bon accord avec l'expérience. L'attribution des bandes observées est aussi discutée.

     

Electronic absorption spectra and EPR spectra of irradiated silicate glasses

The election absorption spectra of sodium silicate glasses in the visible region and the EPR spectra of -irradiated two-component alkali silicate glasses have been studied. It has been established that the electron absorption spectra of these glasses have two bands in the visible region of the spectrum, while the EPR line with g=2.01 consists of two components. A comparison of the absorption spectral data with the EPR spectra showed that the band having a maximum around 4400 å and the -component of the doublet with g=2.01 are associated with the same hole center, of the type Si-O^–... Me⁺ while the band having a maximum around 6200 å and the -component of the doublet arise from a hole center of the type Si-O^–. The change in the ratio of the intensities of the - and -components with changes in the concentration and type of alkali metal is explained.     

Electronic absorption spectra of styrene heteroanalogs

Conclusions The UV bands for styrene heteroanalogs, as in the case of butadiene heteroanalogs, are shifted toward longer wavelengths upon the introduction of several heteroatoms into one fragment and toward shorter wavelengths upon the introduction of the heteroatoms into different fragments.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2585–2586, November, 1987.     

Electronic absorption spectra and protolysis of 4- and 5-azaindan-1,3-diones

The protolytic equilibria in a series of 2-aryl-substituted 4- and 5-azaindan-1,3-diones and the corresponding N-methylbetaines and 5,6-benzo analogs were studied by spectrophotometry. The substantial difference between the 4- and 5-aza derivatives is explained by the different effect of the anionic system on the Tr-electron density and the reactivities of the nitrogen atoms in the 4 and 5 positions. The protonation and deprotonation constants of the dipolar ions correlate linearly with the constants of the substituents in the 2-phenyl ring. In the case of 5,6-benzo-4-azaindan-1,3-diones, the keto group of the azaphthaloyl ring is protonated along with the dipolar ion in strongly acidic media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1382–1386, October, 1972.     

Electronic absorption spectra of 3-β-carboxyethylrhodanine and its 5-arylidene derivatives

The UV spectra of 3--carboxyethylrhodanine and its 5-arylidene derivatives comprise four bands. The first absorption band with a peak at 239 m is not very characteristic of rhodanines. The second band, connected with the presence of the chromophore {\text{N}}{}^{\text{\_}}{\text{C = S}} \hfill \\ {\text{ |}} \hfill \\ \end{gathered} $$ " align="middle" border="0"> , is characterized by peaks in the 243–281 m region.The peak of the third absorption band at about 300 m, is connected with the presence of an amide chromophore, which shifts bathochromically on introduction of a benzylidene group; subsequent introduction of nitro groups results in its being displaced hyposochromically. The most characteristic feature of the 5-arylidene derivatives is formation of a very intense K absorption band in the 360–466 m region, superimposed on the corresponding low-intensity 3--carboxyethylrhodanine absorption band.     

Electronic absorption spectra of selenocarbonyl and thiocarbonyl compounds

Electronic absorption spectra of a variety of thiocarbonyl and selenocarbonyl compounds have been compared to point out their similarities. Interesting correlations between the absorption maxima and electronegativities of substituents in both the seleno- and thio-carbonyl compounds have been reported.     

Electronic absorption spectra and acidities of heteroaromatic thiols

The electronic absorption spectra of a number of substituted and unsubstituted thiophene-, benzothiophene-, and benzofuranthiols were studied, and their ionization constants were determined by establishment of the dependence of the optical densities of aqueous alcohol solutions of them on the pH.Translated from Khimiya Getero-tsiklicheskikh Soedinenii, No. 10, pp. 1313–1314, October, 1980.     

Electronic absorption spectra of pyrylium and benzodihydrochromenylium salts

The electronic absorption spectra of benzodihydrochromenylium, tetrahydrochromenylium, and dichloropyrylium salts were studied for the first time. It was noticed that intramolecular charge transfer takes place mainly between the substituent at position 4 of the pyrylium ring and the π-system of the cation as a whole, while the bathochromic shift depends substantially on the geometry of the molecule. It was shown that the chlorine atoms have an effect on the form of the spectra when they are introduced into the ring of the pyrylium cation and into the aryl substituents. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1152–1159, August, 2008.     

Electronic absorption spectra of hydrogen bonded amides

The vacuum ultraviolet absorption spectra of various hydrogen bonded amides were measured at various temperatures and concentrations. It was found that the characteristic absorption bands of amides, which appear at 180–190 m, greatly change by hydrogen bonded dimer formation and moreover their changes are sensitive to the relative orientation of the monomers. That is to say, they shift to shorter wavelengths by about 6000 cm^–1 by the hydrogen bonded ring dimer formation and shift to longer wavelengths by about 3000 cm^–1 by the hydrogen bonded chain dimer formation. The theoretical consideration on the energy level splittings due to hydrogen bonded dimer formation explained satisfactorily these observations. The results seem to be important in connexion with the determination of the configurations of polymers which contain peptide bonds as a unit.

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Zusammenfassung Vakuum-UV-Absorptionsspektren verschiedener Amide, die H-Brücken ausbilden, wurden vermessen. Die charakteristische Bande der Amide bei 180–190 m wird durch H-Brücken in Abhängigkeit von der Form des gebildeten Dimeren verschoben: so ist die Verschiebung im Falle der Ringbildung +6000 cm^–1, im Falle linearer Verkettung –3000 cm^–1. Dies Phänomen wird theoretisch erklärt. Die Ergebnisse sind für die Strukturaufklärung von polymeren Amiden von Bedeutung.

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Résumé Les spectres d'absorption U.V. dans le vide ont été mesurés pour différentes amides formant des liaisons hydrogène. La bande caractéristique des amides vers 180–190 m. est déplacée lors de la formation d'une liaison hydrogène: pour des dimères ce déplacement est de +6000 cm^–1 lors de la formation d'un composé cyclique et de –3000 cm^–1 lors de la formation d'un composé linéaire. On explique théoriquement ce phénomène. Les résultats ont une signification pour la compréhension de la structure des amides polymères.

     

Electronic absorption spectra of some benzenechromiumtricarbonyl derivatives

Absorption spectra of some arenechromiumtricarbonyl derivatives have been studied. The linear dependence of the extinction coefficient of the longer wavelength absorption band on σ_p⁺ constants of substituents in a benzene ring has been established and it has been shown that a longer wavelength band is a band of intramolecular charge transfer from the central chromium atom to π-bonded arene.