Ensembles of rings with a coumarin unit.

Autor: Doroshenko, A., Posokhov, E., Belokon', Ya., Kovalenko, S., Ivanov, V., Ponomarev, O.
Zdroj: Chemistry of Heterocyclic Compounds; Oct1997, Vol. 33 Issue 10, p1177-1184, 8p
Abstrakt: We have investigated the luminescent spectral properties of 3-(2-R-thiazol-4-yl)coumarins (R=CH3, CH2CH, Ar) and some isomeric 3-(4-R-thiazol-2-yl)coumarins (R=Ar) with substituents of different electronic types both in the coumarin and in the aryl moieties. We have obtained estimates of the rate constants for primary photophysical processes: emission of fluorescence and nonradiative degradation of the electronic excitation energy. We have calculated the matrix elements for the spin-orbit coupling operator, and based on these matrix elements we have calculated the intersystem crossing rate constants. We have shown that deterioration of the fluorescent properties of the studied thiazolyl derivatives of coumarin when π-conjugated moieties are introduced into the thiazole ring is determined by the enhancement of the spin-orbit interaction in a system of levels of the π, π-type. [ABSTRACT FROM AUTHOR]
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