One-Electron Reduction of N21,N22-Bridged Porphyrin Hydroperchlorate to a Stable Phlorin Radical by 1-Benzyl-1,4-Dihydronicotinamide

Abstract

N21,N22-(1,2-Diphenyletheno)-bridged octaethylporphyrin hydroperchlorate underwent one-electron reduction to give a thermally stable phlorin radical when treated with 1-benzyl-1,4-dihydronicotinamide (BNAH). BNAH reduced, in the presence of acid, the same porphyrin to a two-electron reduced product, N21,N22-(1,2-diphenyletheno)octaethyl-15H-phlorin, in contrast to the NaBH4-reduction to N21,N22-(1,2-diphenyletheno)octaethyl-5H-phlorin.

Biladienones from the Photooxidation of a meso-gem-Disubstituted Phlorin: Crystal and Molecular Structures of the 3N + O Coordinated Nickel(II) and Copper(II) Complexes

“…Phlorins are nonaromatic isomers of chlorins and are produced after reduction or addition of nucleophiles to the porphyrins macrocycle. − The stability of most phlorins is limited. Only in a few favorable cases, when stabilized by steric hindrance, ring deformation, or complexation by high valent metals, can these compounds be isolated in a pure state. − The general decomposition process is a simple oxidation to the parent porphyrin, but the irreversible meso addition of a carbon nucleophile, viz., an alkyl group, does not allow this reaction to proceed. We isolated such a phlorin ( 1 ) by addition of n -butyllithium to meso -tetraphenylporphyrin, and although highly unstable toward oxidation, it could be fully characterized.…”