Copper(i) complexes of 6,6′-disubstituted 2,2′-bipyridine dicarboxylic acids: new complexes for incorporation into copper-based dye sensitized solar cells (DSCs)

Abstract

Synthetic approaches to 6,6′-disubstituted-2,2′-bipyridine ligands bearing carboxylic acid substituents at the 4,4′ or 5,5′-positions are described. Copper(I) complexes with these ligands have been prepared for use in copper-based dye-sensitized solar cells. The single-crystal structures of 6,6′-dimethyl-2,2′-bipyridine-4,4′-dicarboxylic acid (H₂4), [H₃6][CF₃CO₂]·2CF₃CO₂H (H₂6 = 6,6′-diphenyl-2,2′-bipyridine-4,4′-dicarboxylic acid) and 4[Cu(H₂2)(H2)]·3H₂O (H₂2 = 6,6′-dimethyl-2,2′-bipyridine-5,5′-dicarboxylic acid) are described, as well as those of the intermediates (1E,5E)-1,6-di(2-furyl)hexa-1,5-diene-3,4-dione and 4,4′-di(2-furyl)-6,6′-dimethyl-2,2′-bipyridine (3), and the copper(I) complex [Cu(3)₂][PF₆]. The roles that classical and non-classical hydrogen bonding and π-stacking interactions play in determining the solid-state packing in these structures are discussed. Preliminary studies of DSCs with these complexes are reported.