Preparation, photophysical, and electrochemical properties of two polynuclear Ru(II) polypyridyl complexes containing imidazole-based ligands

摘要

A tripodal ligand L~1 and dipodal ligand L~2 containing imidazole rings have been synthesized by the reaction of l,10-phenanthroline-5,6-dione with 2,2'-bipyr-idine-4,4'-dicarbaldehyde and 4-methyl-2,2'-bipyridine-4'-carbaldehyde, respectively, in the presence of ammonium acetate. Both ligands have two kinds of nonequivalent coordinating sites: one involving the phenanthroline moiety and the other involving the 2,2'-bipyridine moiety. The Ru(H) complexes, [(bpy)6Ru3(L~1)](PF6)6 and [(bpy)4Ru2-(L~2)](PF6)4 (bpy = 2,2'-bipyridine), have been obtained by refluxing Ru(bpy)2Cl2·2H2O with each ligand in solution. The two complexes display MLCT absorptions at 465 and 480 nm, respectively, and emission at 665 and 675 nm, respectively, in CH3CN solution. Electrochemical studies of both complexes show one Ru(II)-centered oxidation at around 1.29 V and three ligand-centered reductions.