Spectro- and electrochemical studies of some ruthenium and osmium complexes of 2-(2′-pyridyl)benzimidazole;: complexes with intra-molecular charge transfer

Reaction of Ru-3(CO)(12), with 2-(2 ' -pyridylbenzimidazole (HPBI) resulted in the formation of Ru(CO)(3)(HPBI) (I) complex. In presence of pyridine or dipyridine, the two derivatives [Ru(CO)(3)(HPBI)].Py (II) and [Ru(CO)(3)(HPBI).dpy (III) were isolated. The corresponding reactions of Os-3(CO)(12) yielded only one single product; Os(CO)(2)(HPBI)(2) (IV). Spectroscopic studies of these complexes revealed intramolecular metal to ligand CT interactions. Reactions of RuCl3 with NPBI gave three distinct products; [Ru(HPBI)(2)Cl-2]Cl (V), [Ru(HPBI)(dipy)Cl-2]Cl (VI) and [Ru(PBI)(2)(py)(2)]Cl (VII). The UV-vis studies indicated the presence of intramolecular ligand to metal CT interactions. Electrochemical investigation of the complexes showed some irreversible, reversible and quasi-reversible redox reactions due to tautomeric interconversions through electron transfer. (C) 2001 Elsevier Science B.V. All rights reserved.