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Triplet-state Photophysics and Transient Photochemistry of Cyclic Enethiones A Laser Flash Photolysis Study

Bhattacharyya, Kankan and Das, Paritosh K and Ramamurthy, Vaidhyanathan and Rao, V Pushkara (1986) Triplet-state Photophysics and Transient Photochemistry of Cyclic Enethiones A Laser Flash Photolysis Study. In: Journal of the chemical society-faraday transactions ii, 82 . pp. 135-147.

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The triplets of four cyclic enethiones, including thiocoumarin, have been investigated by nanosecond laser flash photolysis. Data are presented for transient spectra and kinetics associated with triplets, quantum yields of intersystem crossing and singlet oxygen photosensitization. The quenching of the thiocoumarin triplet (A:, = 485 nm, E:,, = 8.8 x lo3 dm3 mol-' cm-'in benzene) by several olefins, amines and hydrogen donors occurs with rate constants of 107-5 x lo9 dm3 mol-' s-'; the lower limits of quantum yields ( c#+~) for the related photoreactions, estimated from ground-state depletion, are generally small (0.0-0.1 1 in benzene, except for good hydrogen donors, namely, p-methoxythiophenol and tri-n-butylstannane) . The radical anion of thiocoumarin (A,,, = 405-435 nm) is formed in two stages upon triplet quenching by triethylamine in acetonitrile; the fast component is the result of direct electron transfer to the triplet and the slower component is assigned to secondary photoreduction of the thione ground state by the a-aminoalkyl radical derived from the triethylamine radical-cation.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Royal soc chemistry.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Depositing User: K.S. Satyashree
Date Deposited: 28 Jan 2010 11:17
Last Modified: 19 Sep 2010 05:41
URI: http://eprints.iisc.ac.in/id/eprint/22355

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