A laser flash photolysis study of pivalothiophenone triplets. Steric and electronic effects in thione photoreaction kinetics

K. Bhattacharyya, V. Ramamurthy, P. K. Das

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Upon laser pulse excitation (λex = 532 nm) into the lowest-lying 1(n,π*) band system, pivalothiophenones in benzene solutions give rise to short-lived triplets (λmaxT = 325-335 nm, εmaxT = (11-15) × 103 M-1 cm-1) with quantitative intersystem crossing efficiencies. The triplet yields decrease slightly (by 10-30%) upon changing λex to 308 nm (i.e., upon excitation into S2). Kinetic data are presented for intrinsic triplet lifetimes, self-quenching, and quenching by oxygen, di-tert-butylnitroxy radical, and various reagents capable of interacting with the triplets via energy, electron, or hydrogen-atom transfer and by biradical formation (possibly leading to cycloaddition). The mechanisms of the quenching processes are discussed. Relative to rigid aromatic thiones, namely, xanthione and thiocoumarin, the interaction of pivalothiophenone triplets with most of the quenchers are kinetically inefficient. This is interpreted primarily as a manifestation of the steric crowding at positions α to the thiocarbonyl group.

Original languageEnglish (US)
Pages (from-to)5626-5631
Number of pages6
JournalJournal of physical chemistry
Volume91
Issue number22
DOIs
StatePublished - Jan 1 1987
Externally publishedYes

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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