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Laser Flash Photolysis Formation and Direct Kinetic Studies of Manganese(V)-Oxo Porphyrin Intermediates

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journal contribution
posted on 23.09.2003, 00:00 by Rui Zhang, Martin Newcomb
Irradiation of porphyrin-manganese(III) perchlorate complexes in acetonitrile with 355 nm laser light gave MnV-oxo intermediates that were characterized by their UV−vis spectra and reactivities. The MnV-oxo species of tetrakis(pentafluorophenyl)porphyrin (2), tetraphenylporphyrin (4), and tetra-(4-(N-methylpyridiniumyl))porphyrin (6) were generated. Second-order rate constants for reactions of 2 with substrates were as follows:  6.1 × 105 M-1 s-1 (cis-stilbene), 1.3 × 105 M-1 s-1 (diphenylmethane), 1.3 × 105 M-1 s-1 (ethylbenzene), and 0.55 × 105 M-1 s-1 (ethylbenzene-d10). In oxidations of cis-stilbene and diphenylmethane, the order of reactivity of the MnV-oxo species was 2 > 6 > 4.

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