New ruthenium(II) complexes of α,α′-diimines. Synthesis, electrochemical and optical spectral properties of mononuclear complexes containing aryl(2-pyridylmethylene)amine and 2,2′-bipyridine ligands

Abstract

The tris-chelated complexes, [RuL_n(bipy)_{3 –n}][ClO₄]₂·H₂O [L = aryl(2-pyridylmethylene)amine, bipy = 2,2′-bipyridine, n= 0–3], have been prepared based on a direct and general route. For [RuL₃]²⁺, the geometry has been assessed by ¹H NMR spectroscopy. All the complexes show metal-to-ligand charge transfer (m.l.c.t.) transitions in the visible range at ca. 475 nm. Preliminary results of emission spectra are also described briefly. The metal oxidation as well as ligand reductions for the complexes have been studied electrochemically in acetonitrile using different working electrodes. It has been shown, for the mixed L–bipy complexes, that the reductions of co-ordinated L occur at comparatively lower negative potentials. The correlation between the electrochemical properties and v_c.t.(absorption) is discussed.