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RESEARCH PRODUCT

Electron-Transfer Kinetics for Generation of Organoiron(IV) Porphyrins and the Iron(IV) Porphyrin π Radical Cations

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Homogeneous electron-transfer kinetics for the oxidation of seven different iron(III) porphyrins using three different oxidants were examined in deaerated acetonitrile, and the resulting data were evaluated in light of the Marcus theory of electron transfer to determine reorganization energies of the rate-determining oxidation of iron(III) to iron(IV). The investigated compounds are represented as (P)Fe(R), where P = the dianion of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin (OETPP) and R = C6H5, 3,5-C6F2H3, 2,4,6-C6F3H2, or C6F5 or P = the dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) and R = C6H5, 2,4,6-C6F3H2, or 2,3,5,6-C6F4H. The first one-electron transfer from (P)Fe(R) to [Ru(bpy)3]3+ (bpy = 2,2‘-bipyridine) leads to an Fe(IV) σ-bonded complex, [(P)FeIV(R)]+, and occurs at a rate which is much slower than the second one-electron transfer from [(P)FeIV(R)]+ to [Ru(bpy)3]3+ to give [(P)FeIV(R)]•2+. The one- or two-electron oxidation of each (OETPP)Fe(R) or (OEP)Fe(R) deriv...