Synthesis and characterization of cis-(2,2′-bipyridine)(2,2′-biquinoline) dichlororuthenium(II) and its co-ordination chemistry with imidazole derivatives

Abstract

The reactions of cis-[Ru(bipy)(bquin) Cl₂](bipy = 2,2′-bipyridine, bquin = 2,2′-biquinoline) with several imidazole derivatives have been studied. Substitution of only one chloride ligand takes place exclusively trans to bquin, resulting in the synthesis of cis-[Ru(bipy)(bquin)(L)Cl]PF₆(L = Him, 1-mim or 5-mim; Him = imidazole, 1-mim = 1-methylimidazole, 5-mim = 5-methylimidazole). This substitution preference for imidazoles indicates that bquin has a stronger electronic trans influence than bipy, and that the steric effects of bquin do not appear to obstruct the approach of a substituting ligand. By substitution of the second chloride the compounds cis-[Ru(bipy)(bquin)L₂][PF₆]₂ and cis-[Ru(bipy)(bquin)(1-mim)-(Him)][PF₆]₂ were isolated. The properties of the compounds have been studied by ¹H NMR spectroscopy and electrochemistry. The studies show that cis-[Ru(bipy)(bquin)Cl₂] incorporates potential covalent binding properties for biomolecules like histidine and DNA.