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 1H NMR studies (−50–60 °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 TPFC’s.