Highly electrochemiluminescent Ru(II) complexes containing 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-one ligand

A series of new ruthenium(II) complexes containing 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-one (DTDP) ligand, such as [Ru(DTDP)n(L)3−n]2+ (L = 2,2′-bipyridyl (bpy), 4,4′-dimethyl-2,2′-bipyridyl (dmbpy), o-phenanthroline (o-phen), 5-chloro-o-phenanthroline (o-phen-Cl), 2,2′-bipyridine-4,4′-dicarboxaldehyde (bpy-(CHO)2), n = 1, 2, 3) were synthesized and examined as ECL materials. All the complexes were characterized in terms of electrochemical redox potential and relative ECL intensity, and were compared to the well-known tris(o-phenanthroline) ruthenium(II) complex. Most of the synthesized Ru(II) complexes containing the DTDP ligand exhibited more intense ECL emissions than [Ru(o-phen)3]2+. In particular, the ECL intensities of [Ru(DTDP)(o-phen)2]2+ and [Ru(DTDP)(bpy-(CHO)2)2]2+ were observed to be as high as 9-fold and 20-fold greater, respectively, than the ECL intensity of [Ru(o-phen)3]2+.