Syntheses of Homochiral Multinuclear Ru Complexes Based on Oligomeric Bibenzimidazoles

The homochiral multinuclear Ru complexes of the oligomeric bibenzimidazoles were synthesized using Λ-[Ru(bpy)₂(py)₂][(−)-O,O‘-dibenzoyl-l-tartrate]·12H₂O as an enantiomerically pure building block. The complexations proceed with the retention of configuration to provide well-defined mononuclear, dinuclear, tetranuclear, and octanuclear Ru complexes successfully. The optical purity and the absolute configurations of the complexes were determined by NMR and circular dichroism spectrometry. The rare X-ray structure of a tetranuclear complex Λ₄-[(Ru(bpy)₂)₄(bis(BiBzIm))](PF₆)₄ was resolved. The crystallographic analysis reveals that all the four Ru centers have Λ octahedral configurations, with a Ru−Ru separation of 5.509 Å across the bridging bibenzimidazole ligand, which maintains near coplanarity. The UV−vis spectroscopic and electrochemical properties of the homochiral multinuclear assemblies were studied, indicating weak electronic communications between the metal centers.