Crystal structures of dicarboxy-2,2′-bipyridyl complexes: the role of hydrogen bonding and stacking interactions

Abstract

The crystal structures of three complexes of dicarboxy-2,2′-bipyridyl ligands, 5,5′-dicarboxy-2,2′-bipyridyl (1) and 4,4′-dicarboxy-2,2′-bipyridyl (2) are reported. [Rh(1H)₃] shows two interpenetrating, homochiral rhombohedral networks linked by short carboxylate–carboxylic acid hydrogen bonds, in which each complex acts as a node for six hydrogen bonds. [Ru(1H₂)(1H)₂] forms only four such hydrogen bonds, leading to the formation of heterochiral chains held together by stacking between bipyridyls. [Co(2H)₃] can in principle form six hydrogen bonds, but in practice forms only four in a layer structure where stacking interactions are important. This is attributed to differences in molecular shape.