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Photochemistry of thioxanthen-9-one-10,10-dioxide: A remarkably reactive triplet excited state

Paper ID Volume ID Publish Year Pages File Format Full-Text
26683 43970 2011 7 PDF Available
Title
Photochemistry of thioxanthen-9-one-10,10-dioxide: A remarkably reactive triplet excited state
Abstract

The steady state photolysis of thioxanthen-9-one-10,10-dioxide (1) in dichloromethane does not result in any product formation. In hydrogen donor solvents, such as 2-propanol, toluene or cyclohexane, the formation of the corresponding pinacol was readily observed. The phosphorescence spectrum of 1 in EPA, at 77 K, reveals a triplet energy of 66.3 kcal mol−1. Laser flash photolysis irradiation of a degassed acetonitrile solution of 1 led to the formation of its triplet excited state (λmax = 375 and 520 nm, τ = 11 μs) that was quenched by oxygen, β-carotene and 1,3-cycloexadiene at a diffusion controlled rate constant. The quenching rate constants for the triplet of 1 with 1,4-cyclohexadiene, methanol, ethanol, 2-propanol, cyclohexane, substituted phenols and amines were determined, ranging from 7.1 × 106 (for methanol) to 3.1 × 1010 L mol−1 s−1 (for triethylamine). From the quenching rate constants observed for the triplet excited state and from the steady state photolysis, it was concluded that the remarkable reactivity of 1 is due to the n,π* character of the carbonyl chromophore.

► Triplet state reactivity of thioxanthen-9-one-10,10-dioxide in acetonitrile. ► The phosphorescence spectrum reveals a triplet energy of 66.3 kcal mol−1. ► The quenching rate constants measured for hydrogen and electron donors show an extremely reactive triplet state. ► The remarkable reactivity of this ketone is due to the n,λ* character of its carbonyl chromophore.

Keywords
Laser flash photolysis; Thioxanthen-9-one-10,10-dioxide; Triplet excited state
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 225, Issue 1, 1 December 2011, Pages 135–141
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
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Price was $35.95
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