Novel meso-substitution reactions of metalloporphyrins

Solutions of octaalkyl metalloporphyrin Π cation radicals react with nucleophiles such as nitrite, chloride, pyridines, imidazole, cyanide, triphenylphosphine, thiocyanate, acetate, and azide, to produce the corresponding meso-(methine) substituted metalloporphyrins. Demetalation then gives the appropriate meso-substituted porphyrin. Circumstantial evidence suggests that the 7Π cation radical reacts (possibly in a complexed or aggregated form) with the nucleophile, and that the corresponding Π dication of the metalloporphyrin or the radical (produced by oxidation of the nucleophile) is not involved in the combination step of the reaction.