Synthesis, structures and electrochemical characterization of ferrocene-substituted porphyrin and porphodimethene

Abstract

Condensation of ferrocenecarboxaldehyde and dipyrrolylmethane gave 5,15-diferrocenyl-2,8,12,18-tetraethyl-3,7,13,17-tetramethyl-5,15-dihydroporphyrin (H(2)1) and 5,15-diferrocenyl-2,8,12,8-tetraethyl-3,7,13,17-tetramethylporphyrin (H(2)2) in 31 and 49% yield, respectively. Structures of H(2)1 . CHCl3 and H(2)2.0.5C(6)H(5)Me have been determined by X-ray diffraction. Compound H(2)1 has syn-axial configuration and H(2)2 has syn configuration of two ferrocenyl groups. Compound H(2)1 was only proven to be an intermediate species of H(2)2 in the photooxidation pathway. The large steric bulkiness of the ferrocenyl group permitted the isolation of compounds H(2)1 and H(2)2 directly from the oxidation reaction of 5,15-diferrocenyl-2,8,12,18-tetraethyl-3,7,13,17-tetramethylporphyrinogen. Porphodimethene H(2)1 has exceptional stability toward air and light in the absence of acid. Electrochemically, ferrocene subunits of H(2)1 are oxidized with a reversible two-electron transfer process (0.33 V), while those of H(2)2 are oxidized with two reversible one-electron transfer processes (0.06 and 0.27 V). (C) 2000 Elsevier Science B.V. All rights reserved.