K.Suryanarayana Rao

Vibrational spectra of ortho-, meta and para-fluoroanilines

Abstract The infra-red spectra of ortho -, meta - and para -fluoroanilines in the liquid state have been investigated in the region 650–4000 cm −1 . Tentative assignments of the observed frequencies have been made by assuming C 2 v , symmetry for para -fluoroaniline and C 3 , symmetry for ortho - and meta -fluoroanilines.

A new method for estimating excited state dipole moments of molecules from the solvent effect on their electronic spectra

Abstract Some comments are made on the paper entitled “Excited state dipole moments of some monosubstituted benzenes from the solvent effect on electronic absorption spectra” by Prabhumirashi et al . ( Spectrochim. Acta 39A , 663,1983) and a new method, which has been tested on some molecules and found satisfactory, is suggested for estimating the excited state dipole moment of molecules from the solvent effect on their electronic spectra.

Infrared and electronic absorption spectra of some trisubstituted benzenes

Abstract The electronic absorption spectra of 2,3-, 2,4-, 2,5-, 2,6- and 3,4-difluorobenzonitriles, 3,4-difluoroaniline and 3,4-difluoroanisole in the ultraviolet region in vapour phase have been recorded on medium quartz and Hilger large quartz spectrographs and on a Hitachi model 150-20 UV-VIS ratio recording spectrophotometer. All the molecules investigated have exhibited two π* ← π band systems corresponding to 1 B 2 u ← 1 A 1 g (λ2600 A) and 1 B 1 u ← 1 A 1 g (λ2100 A) systems of benzene. The infrared absorption spectra of all the molecules studied have also been recorded and analysed. These infrared data have been taken to help analyse the u.v. spectra of the molecules studied.

Determination of excited state electric dipole moment of a molecule from solvatochromic shift measurements—a new approach

Abstract A new approach to the determination of the electric dipole moment of a molecule in an excited electronic state from the method of solvent-shifts is indicated.

π* ← n and π* ← π absorption spectra of aminopyrazine

Abstract π* ← n and π* ← π absorption spectra of aminopyrazine have been recorded and analysed assuming C s symmetry for the molecule.

Electronic absorption spectra of 2,3- and 2.5-dimethylpyrazines

Abstract The electronic absorption spectra of 2,3- and 2,5-dimethylpyrazines were recorded and analysed considering C 2ν and C 2h symmetry for the molecules, respectively. Vibrational analysis of the electronic spectra of these molecules has shown the existence of a vibronic interaction between two electronic states of both the molecules through an out-of-plane bending mode.

Electronic absorption spectrum of 6-chloroindole

Abstract Despite our studies on the π* ←π system in some substituted indoles (E. V. Huded, N. H. Ayachit, M. A. Shashidhar and K. Suryanarayana Rao, Spectrochim. Acta 42A, 1407 (1986) and the references mentioned therein ) the available data are limited. We therefore report and interpret the vapour phase electronic absorption spectrum and infrared spectrum of 6-chloroindole.

Determination of excited state electric dipole moment of the isomeric fluorophenylisocyanates from solvatochromic shift measurements

The excited state electric dipole moments of three isomeric fluorophenylisocyanates are determined using the method of solvatochromic shift measurements recently suggested from our laboratory.

Infra-red and electronic absorption spectra of 2-bromopyrimidine

Abstract The electronic absorption spectrum of 2-bromopyrimidine in the u.v. region has been recorded in vapour phase and in solution phase in different solvents. Only one system has been observed in vapour phase and it has been identified as π* ← n transition. In solution phase two systems have been identified. The system on the longer wavelength side has been identified as corresponding to the one observed in vapour phase while the other one has been assigned to a π* ← π transition. The infrared spectrum of this molecule has also been recorded and analysed. Help of these i.r. data has been taken to analyse the u.v. spectrum of 2-bromopyrimidine, considering the molecule as belonging to C 2υ point group.

π* ← n electronic absorption spectrum of 2,6-dichloropyrazine

Abstract The π* ← n electronic absorption system of 2,6-dichloropyrazine, corresponding to the 1 B 3 u ← 1 A 1 g transition of pyrazine, has been recorded in the vapour phase and in solution in cyclohexane. A vibrational analysis of this system has been proposed and it is shown that vibronic interaction between two excited states of 2,6-dichloropyrazine exists. Another system is observed in the solution spectrum of this molecule in cyclohexane and it is shown to be a π* ← π transition analogous to the 1 B 2 u ← 1 A 1 g transition in pyrazine.