Electron transfer reaction of Cu(II) porphyrin complex: Effect of structural deformation on the electron self-exchange rate

Homogeneous one-electron oxidation reaction of the sterically constrained nonplanar Cu(II) 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin complex ([Cu(OETPP)]) by Cu2+ giving the π-cation radical of [Cu(OETPP)] was investigated spectrophotometrically in acetonitrile. The electron self-exchange rate constant of the [Cu(OETPP)]+radical dot/0 couple was determined to be 9.3 × 103 M−1 s−1 at T = 25.0 °C using the Marcus cross relation for the outer-sphere electron transfer reaction, and the relatively slow self-exchange reaction as compared with those for the planar Cu(II) porphyrin complexes was ascribed to the significant deformation of the complex accompanying the oxidation reaction.