• S K Sarkar

      Articles written in Journal of Chemical Sciences

    • Effect of ring aza substitution on the luminescence of aromatic ketones. Luminescence of isomeric acetylpyridines

      S K Sarkar S K Ghoshal G S Kastha

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      The absorption and luminescence characteristics of 2-,3-and 4-acetyl-pyridines (ACP) and acetophenone have been examined in polar and nonpolar media at room temperature and low temperature (77K). All the ACP exhibit intense and structured phosphorescence emission of* character. Though the triplet yields of these ketones are very high, the phosphorescence quantum yield and lifetime of ACP decrease significantly in the order 4-ACP>3-ACP>2-ACP> acetophenone. The distinctive differences in the spectral properties and the luminescence characteristics of ACP from their phenylanalogue have been interpreted in terms of the perturbing influences of the inductive effect of the pyridinic nitrogen, the vibronic interaction between the* andππ* states and the photochemical reaction occurring from the lowest triplet state.

    • Correlative studies on the absorption and emission characteristics of isomeric chlorobenzonitriles

      A K Maiti S K Sarkar G S Kastha

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      Absorption, fluorescence and phosphorescence characteristics of isomeric chlorobenzonitriles have been studied and similarities and differences in these have been noted and compared with those of analogous compounds reported in the literature. The variations in absorption spectral characteristics have been explained and the correlation between the dipole moments of the molecules and the energy of the energy of the para isomers has been elucidated. Analyses of the phosphorescence data have led to the conclusion that internal heavy atom spin-orbit coupling effect is important in the chlorobenzonitriles and that the radiative and nonradiative rates from their triplet states may be reasonably rationalized on this basis.

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