Synthetic, crystallographic and electrochemical studies of thienyl-substituted corrole complexes of copper and cobalt

Abstract

The TFA-catalyzed condensation of 5-(thienyl)dipyrromethane with thiophene carboxaldehyde allows for the formation of the thienyl meso-substituted 5,10,15-tris(2-thienyl)corrole H-3(T2TC) (1) and the 5,10,15-tris(3-thienyl)corrole H-3(T3TC) (2). These ligands undergo metalation with copper and cobalt acetate to yield the four respective metallocorroles. Single-crystal X-ray crystallographic solutions for Cu(T2TC) (3), Co(T2TC)(PY)(2) (5) and Co(T3TC)(PY)(2) (6) have been obtained, confirming the direct pyrrole-pyrrole link and axial pyridine groups in the case of the cobalt structures. Cyclic voltammetry data indicated the 2-thienyl derivatives are more difficult to oxidize when compared to trispentafluorophenyl corroles (TPFC). Both metal complex isomers are comparably stable towards the formation of dinuclear products resulting from intermolecular C-C coupling. Soret bands for both ligands and complexes have been obtained and variable temperature H-1 NMR studies (-50-60 degrees C) for 3 and 4 reveal a fluxional rotational behavior for the three thienyl substituents believed to impart a less electron withdrawing effect on the corrole core, opposed to the TPFCs. (C) 2005 Elsevier Ltd. All rights reserved.