One-Electron Oxidation of Chlorophyll a and (Tetraphenylporphyrinato)cobalt(II) by Various Metalloporphyrin Cation Raducals. Kinetic Spectrophotometric Studies

Article abstract of DOI:10.1021/j150614a032

One-electron oxidations of various metalloporphyrins in dichloroethane solutions were studied by kinetic spectrophotometric pulse radiolysis.Co(II)TPP (TPP=tetraphenylporphyrin) was found to produce Co(III)TPP while the Cd(II), Cu(II), Pb(II), and VO complexes, like the ZnTPP and MgTPP, yield the cation radicals.Ni(II)TPP is oxidized at the metal center in the presence of pyridine but at the ligand in its absence.The subsequent one-electron oxidation of chlorophyll a and Co(II)TPP by the above cation radicals was also followed.The rate constants for these reactions were found to be mostly in the range of 3E8 - 5E8 M^-1s^-1, much lower than the expected diffusion-controlled rates.