K. Ohkubo, Takashi Nanjo, S. Fukuzumi
Oct 10, 2006
Citations
0
Influential Citations
69
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
Photooxygenation of triphenylphosphine (Ph 3 P) to triphenylphosphine oxide (Ph 3 P=O) with molecular oxygen (O 2 ) occurs under photoirradiation of 9-mesityl-10-methylacridinium perchlorate ([Acr + -Mes]ClO 4 - ) which acts as an efficient electron-transfer photocatalyst. Photooxidation of benzylamine (PhCH 2 NH 2 ) with O 2 also occurs efficiently under photoirradiation of Acr + -Mes to yield PhCH 2 N=CHPh and hydrogen peroxide (H 2 O 2 ). Each photocatalytic reaction is initiated by intramolecular photoinduced electron transfer from the Mes moiety to the singlet excited state of the Acr + moiety to produce the electron-transfer state (Acr·-Mes· + ). The Mes· + moiety oxidizes Ph 3 P and PhCH 2 NH 2 to produce the radical cations (Ph 3 P· + and PhCH 2 NH 2 · + , respectively), whereas the Acr· moiety reduces O 2 to O 2 · - . The produced Ph 3 P· + binds with O 2 · - as well as O 2 , leading to the oxygenated product (Ph 3 P=O). On the other hand, proton transfer from PhCH 2 NH 2 · + to O 2 · - occurs, followed by hydrogen transfer, leading to the dehydrogenated dimer product, PhCH 2 N=CHPh. In each case, the radical intermediates were detected by laser flash photolysis and ESR measurements to clarify the photocatalytic mechanism.