Structure, spectroscopic and electrochemical properties of novel binuclear ruthenium(II) copper(I) complexes with polypyridyl bridging ligands

摘要

Binuclear complexes of the type [(bpy)_2Ru(BL)Cu(PPh_3)_2]~(3+), where bpy = 2,2'-bipyridine, BL = 2,3-di-2-pyridylpyrazine (dpp), 2,3-di-2-pyridylquinoxaline (dpq), or 6,7-dimethyl-2,3-di-2-pyridylquinoxaline (dpqMe_2), were readily formed by the reaction of [Cu(PPh_3)_4]~+ with mononuclear complexes [Ru(bpy)_2(BL)]~(2+). The binuclear complexes are stable in CH_2Cl_2 solution at concentrations above 10~(-3) having equilibrium constants for formation in the range 1000-2500 dem~3 mol~(-1). Single crystal structures for [(bpy)_2Ru(dpp)Cu(PPh_3)_2]~(3+) and [(bpy)_2Ru(dpqMe_2)Cu(PPh_3]~(3+) show distortions of the bridging ligand in the form of twisting and splaying of the ring systems. Electrochemical and UV/Visible data suggest the {Cu(PPh_3)_2}~+ moiety has little affect in stabilising the BL #pi#~* orbital. Resonance Raman spectra show the bichromophoric nature of the visible absorptions of the heteroleptic complexes; both bpy and BL ligand vibrations are enhanced depending on the excitation wavelength. Observation of a Ru-N vibration suggests that the dominant transition in the visible region is Ru(d_#pi#) → BL(#pi#~*)CT.