A comparative study of supramolecular assemblies containing N″-(5,6-dimethyl-1 H-benzimidazol-2-yl)guanidine, 2-guanidinobenzimidazole and their Ni(II) complexes

Abstract

Previous studies have shown that 2-guanidinobenzimidazole and the neutral complex [bis(2-guanidinobenzimidazolo)nickel(II)] are capable of forming extended hydrogen bonded arrays in the solid state, either alone or with other transition metal complexes as well as with organic molecules with complementary hydrogen bonding motifs. Additionally, the complex of the free ligand with phthalimide contains a NHN hydrogen bond so short that it compares with the short hydrogen bonds in some of the ‘proton sponges’. In this paper we report on the molecular structures and simple supramolecular assemblies containing the related ligand N″-(5,6-dimethyl-1 H-benzimidazol-2-yl)guanidine which has a higher p K a than the parent (unsubstituted) ligand and which has steric requirements which mean that it cannot be incorporated into the same supramolecular structures. In particular, we examine the structure of the free ligand, of the complex formed by the ligand and phthalimide and of the extended structure of the neutral bis-ligand nickel(II) complex and dmso. The structures are compared with those mentioned above incorporating the unsubstituted ligand, 2-guanidinobenzimidazole.