Formation and Isolation of a Four‐Electron‐Reduced Porphyrin Derivative by Reduction of a Stable 20π Isophlorin

Abstract

The two‐electron reduction of a diprotonated dodecaphenylporphyrin derivative by Na₂S₂O₄ gave a corresponding isophlorin (Iph) selectively. Formation of Iph was confirmed by spectroscopic measurements and the isolation of tetramethylated Iph. Further reduction of Iph proceeded to form an unprecedented four‐electron‐reduced porphyrin (IphH₂), which was fully characterized by spectroscopic and X‐ray crystallographic analysis. IphH₂, with a unique conformation, could be oxidized to reproduce the starting porphyrin, resulting in a proton‐coupled four‐electron reversible redox system.