Laser-flash-photolysis study of aliphatic thioketone triplets. Self-quenching and singlet-oxygen sensitization

Kankan Bhattacharyya, Challa V. Kumar, Paritosh K. Das, B. Jayasree, Vaidhyanathan Ramamurthy

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Seven aliphatic thioketones, several of them possessing bicyclo[2.2.1]heptane geometries, have been examined for triplet-state behaviour in benzene using laser excitation into their low-lying 1(n, π*) band systems (485-490 and 532 nm). In the case of di-t-butylthioketone (DTBTK) a transient absorption (280-500 nm) was attributable to its triplet (εT ≈ 1.5 × 103 dm3 mol-1 cm-1 at 280 nm). The thioketone triplets were, however, probed in all cases by energy transfer to all-trans-1,6-diphenyl-1,3,5-hexatriene (DPH). Results are presented for triplet lifetimes (0.1-0.6 μs at 1 × 10-3 mol dm-3 thioketone concentration), intersystem-crossing yields (0.85-1.0), self-quenching kinetics [(0.1-7) × 109 dm3mol-1 s-1] and kinetics of energy transfer to DPH [(6-8) × 109 dm3 mol-1 s-1]. The steric crowding at α positions severely hinders the self-quenching interaction in DTBTK. The efficiency of singlet-oxygen formation as a result of DTBTK triplet quenching by oxygen is close to unity (0.85 ± 0.17 in benzene).

Original languageEnglish (US)
Pages (from-to)1383-1393
Number of pages11
JournalJournal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics
Volume81
Issue number9
DOIs
StatePublished - Dec 1 1985
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry

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