No abstract

One-electron oxidation of a series of metallotetraphenylporphyrins (M-TPP) was studied by pulse radiolysis in CCll solutions.The resultant r-radical cations were found to oxidize Co"TPP to Co"'TPP with rate constants of the order of lo5 M-' d, much slower than the diffusion-controlled rates despite the high free energies of these reactions. In the presence of pyridine these electron-transfer reactions were much faster ( 107-10s M-I sd), suggesting that pyridine, as an axial ligand, facilitates the electron transfer between metalloporphyrins.