Photochemical properties of excited triplet state of 6H-purine-6-thione investigated by laser flash photolysis

Maksudul M. Alam, Mamoru Fujitsuka, Akira Watanabe, Osamu Ito

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33 Citations (Scopus)

Abstract

Photochemical reactions of 6H-purine-6-thione (PuT) via the excited triplet state [3(PuT)*] have been studied by means of laser flash photolysis in organic solvents. Transient absorption bands at 475 and 690 nm were assigned to 3(PuT)*. Intersystem quantum yield and the lowest triplet energy of 3(PuT)* were evaluated to be 0.99 and 63 kcal/mol, respectively. The self-quenching rate constant is quite large (2.3 × 109 M-1 s-1 in THF). In photoinduced electron transfer, 3(PuT)* acts as electron acceptor for tetramethylbenzidine, while 3(PuT)* acts as electron donor for p-dinitrobenzene. Rate constants for H-atom abstraction (khT) of 3(PuT)* from benzenethiols, tocopherol, and 1,4-cyclohexadiene are on the order of 108 M-1 s-1. From the Hammett plots of khT for substituted benzenethiols, a negative ρ value indicates that 3(PuT)* has electrophilic character. In the addition reaction of 3(PuT)* toward various alkenes, the electrophilic character of 3(PuT)* was also confirmed. By steady-light photolysis of PuT, purine was produced via 3(PuT)* after H-atom abstraction. On combination of these results, the character of the lowest 3(PuT)* was presumed.

Original languageEnglish
Pages (from-to)1338-1344
Number of pages7
JournalJournal of Physical Chemistry A
Volume102
Issue number8
Publication statusPublished - 1998 Feb 19

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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