Azolium‐Porphyrin Electrosynthesis

Electrochemical oxidation of Zn(II) 2,7,12,17‐tetra‐tert‐butylporphyrin in the presence of a series of azole derivatives (1‐methylimidazole, 1‐vinyl‐1H‐imidazole, 2‐(1H‐imidazol‐1‐yl)pyridine, 1‐methylbenzimidazole, 1‐methyl‐1H‐1,2,4‐triazole, and benzothiazole) affords the corresponding meso‐substituted azolium‐porphyrins in very mild conditions and good yields. It was found that these nucleophiles were strongly ligated to the zinc(II) azolium‐porphyrin complexes. Thus a demetalation/remetalation procedure was performed to recover the non‐azole‐coordinated zinc(II) complexes. X‐ray crystallographic structures of three azolium‐porphyrins were solved. Cyclic voltammetry analyses provided insight into the electron‐withdrawing effect of the azolium substituents.