The new mononuclear Ru III complexes [Ru(ntb)Cl 2 ]Cl (1), [Ru(ntb)Cl 2 ]ClO 4 (1a), and [Ru(mntb)Cl 2 ]Cl (2) (ntb = tris-(benzimidazol-2-ylmethyl)amine, mntb = tris(N-methylbenzimidazol-2-ylmethyl)amine) have been synthesized and characterized. The X-ray crystal structure of 1 reveals that the coordination geometry around the Ru III center is distorted octahedral in which four sites are occupied by the tetradentate ligand ntb and the remaining cis positions by two chloride ions. The stronger Ru-N bzim bonds elongate the Ru-Cl bonds thereby labilizing the coordinated chloride ions. In the electronic absorption spectra the Ru III complexes show two bands corresponding to π(bzim) Ǟ t 2g (Ru) and pπ(Cl -) Ǟ t 2g (Ru) ligand-to-metal charge transfer (LMCT) transitions along with intraligand transitions in the UV region. Complex