Duroquinone triplet reduction, in cyclohexane, ethanol and water, and by durohydroquinone
- 1 January 1976
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 72, 1274-1287
- https://doi.org/10.1039/f19767201274
Abstract
Laser flash spectroscopy has been used to study the lifetime, extinction coefficient, oscillator strength and quantum yield of formation (ϕT) of duroquinone triplet 3Q in solution. Reaction of this triplet with solvent leads in ethanol and cyclohexane to the neutral semiquinone QH. Reaction of this triplet with itself leads in water to the anion Q·– and in cyclohexane and ethanol to the excited singlet 1Q* followed by 3Q. Transient spectra and kinetic measurements demonstrate that triplet-triplet annihilation is the only path for duroquinone photoreduction in water. ϕT in the solvents used is unity (±0.15), ϕ(QH) is 0.4 (±0.1) in ethanol and 0.09 (±0.03) in cyclohexane. Laser flash spectroscopy of the duroquinone + durohydroquinone system gave rise to spectra of the transient species 3Q and QH linked by isobestic points in ethanol and cyclohexane. In water 3Q and Q·– were observed, again linked by isobestic points. The observed reaction 3Q + QH2→ 2 QH allowed a determination of the QH extinction in ethanol and cyclohexane. The formation of a triplet exciplex 3(Q, QH2) is suggested.Keywords
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