Electrochemiluminescent dinuclear Ru(II) complexes assembled with 1,1′-(1,2-ethynediyl)- or dimethlyene-bridged bis(bipyridine) ligands: Synthesis and photophysical and electrochemical properties

Abstract 1,2-Di(2,2′-bipyridin-5-yl)ethane ( BL1 ) and 1,2-di(2,2′-bipyridin-5-yl)ethyne ( BL2 ) were synthesized as new bridging ligands and coordinated to (RuL 2 (acetone) 2 )(PF 6 ) 2 for the preparation of various [Ru(L) 2 (BL)Ru(L) 2 ](PF 6 ) 4 -type dinuclear ruthenium complexes (where BL =  BL1 , BL2 and L = bpy, o -phen, DTDP). The electrochemical redox potentials, spectroscopic properties, and relative electrochemiluminescence intensity of BL1 and BL2 were characterized and compared to those of well-known tris(1,10-phenanthroline)rutheniun(II) [Ru( o -phen) 3 ](PF 6 ) 2 ] complex as a reference. Dinuclear Ru(II) complexes containing the conjugated bridging ligand ( BL2 ) showed much more intense electrochemiluminescent responses than dinuclear Ru(II) complexes with the non-conjugated bridging ligand ( BL1 ). Among the complexes with conjugated bridging ligands, [(DTDP) 2 Ru(bpy-CC-bpy)Ru(DTDP) 2 ](PF 6 ) 4 exhibited enhanced ECL intensities as high as 3.6 times greater than that of the reference, [Ru( o -phen) 3 ](PF 6 ) 2 .