Issue 27, 2012

Improvement of durability of an organic photocatalyst in p-xylene oxygenation by addition of a Cu(ii) complex

Abstract

The catalytic durability of an organic photocatalyst, 9-mesityl-10-methyl acridinium ion (Acr+–Mes), has been dramatically improved by the addition of [{tris(2-pyridylmethyl)amine}CuII](ClO4)2 ([(tmpa)CuII]2+) in the photocatalytic oxygenation of p-xylene by molecular oxygen in acetonitrile. Such an improvement is not observed by the addition of Cu(ClO4)2 in the absence of organic ligands. The addition of [(tmpa)Cu]2+ in the reaction solution resulted in more than an 11 times higher turnover number (TON) compared with the TON obtained without [(tmpa)CuII]2+. In the photocatalytic oxygenation, a stoichiometric amount of H2O2 formation was observed in the absence of [(tmpa)CuII]2+, however, much less H2O2 formation was observed in the presence of [(tmpa)CuII]2+. The photocatalytic mechanism was investigated by laser flash photolysis measurements in order to detect intermediates. The reaction of O2˙ with [(tmpa)CuII]2+ monitored by UV-vis spectroscopy in propionitrile at 203 K suggested formation of [{(tmpa)CuII}2O2]2+, a transformation which is crucial for the overall 4-electron reduction of molecular O2 to water, and a key in the observed improvement in the catalytic durability of Acr+–Mes.

Graphical abstract: Improvement of durability of an organic photocatalyst in p-xylene oxygenation by addition of a Cu(ii) complex

Supplementary files

Article information

Article type
Paper
Submitted
14 Apr 2012
Accepted
14 May 2012
First published
14 May 2012

Phys. Chem. Chem. Phys., 2012,14, 9654-9659

Improvement of durability of an organic photocatalyst in p-xylene oxygenation by addition of a Cu(II) complex

Y. Yamada, K. Maeda, K. Ohkubo, K. D. Karlin and S. Fukuzumi, Phys. Chem. Chem. Phys., 2012, 14, 9654 DOI: 10.1039/C2CP41207A

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