Electrosynthesis, electrochemistry, and crystal structure of the tetracationic Zn-meso-tetrapyridiniumyl-β-octaethylporphyrin

✍ Scribed by A. Giraudeau; S. Lobstein; L. Ruhlmann; D. Melamed; K. M. Barkigia; J. Fajer

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 98 KB
• Volume: 05
• Category: Article
• ISSN: 1088-4246
• DOI: 10.1002/jpp.547

✦ Synopsis

Exhaustive electro-oxidation of ZnOEP in the presence of pyridine and Et ~4~ NPF ~6~ affords in high yield the new tetracationic porphyrin in which the four meso protons of ZnOEP are replaced by four pyridinium groups linked via their nitrogens: [ Zn -5,10,15,20-tetrakis(N-pyridiniumyl)-2,3,7,8,12,13,17,18-octaethylporphyrin]^4+^[Formula: see text], 1. The compound has been characterized by elemental analysis, ^1^ H NMR, and crystallography. The latter confirms the preparative electrosynthetic methodology and molecular structure of 1, and shows the porphyrin skeleton to adopt a severely nonplanar saddle conformation which minimizes steric crowding between the 12 peripheral substituents. As a consequence of the nonplanarity (and the high charge) of the complex, 1 exhibits significant red-shifts of the visible and Soret bands as well as a considerable broadening and loss of intensity of the latter. 1 first undergoes four one-electron reduction steps at the four pyridinium sites before the normal one-electron reduction of the porphyrin π-system.