Coordination behavior of benzimidazole, 2-substituted benzimidazoles and benzothiazoles, towards transition metal ions

Coordination chemistry of benzimidazole and 2-substituted benzimidazole derivatives towards transition metal ions is reviewed. Benzimidazole complexes containing halides or carboxylates derivatives are discussed, as well as the coordination chemistry of 2-substituted benzimidazoles bearing additional nitrogen, oxygen or sulfur atoms as potential binding sites, which may form chelates. The latter ligands give place to a variety of metal-ligand coordination modes. In some cases, these bidentate ligands favour the formation of a six membered ring, by inclusion of a metal ion in a planar delocalized system. Some of the studied 2-substituded benzimidazoles include 2-uroyl, 2-carbamate, 2-benzothiazole, 2-(2-benzothiazolylamino)benzothiazole, 2-(2aminobenzothiazolyl-amino) benzoxazole, 2-(4'-thiazolyl)benzimidazole, 2-((5-methylpyrazol-3yl)methyl)benzimidazole, 2-guanidinobenzimidazole, 2-aminomethylbenzimidazole, 1-(benzimidazol-2-yl)phenolato, 2-(2-benzimidazol-2-yl)pyridine-N-oxide-N,O and N-(benzothiazol-2-yl)-dithiocarbamic methyl ester. It is important to mention that benzimidazole and its derivatives promote intra and inter-molecular interactions, such as hydrogen bonding and stacking, giving place to the formation of molecular aggregates.