A new kind of peripheral carbazole substituted ruthenium(II) complexes for electrochemical deposition organic light-emitting diodes

A new kind of peripheral carbazole substituted ruthenium(II) complexes [Ru(bpy)(2)(tkdp-bpy)(AsF6)(2)] (4) (bpy bipyridine, tkdp-bpy 4,4'-(3,5-bis(6-(9H-carbazol-9-yl)hexyloxy)phenyl) methoxycarbonyl-2,2'- bipyridine) and [Ru(bpy)(2)(dkte-bpy)(ClO4)(2)] (5) (dkte-bpy = bis(4-(9H-carbazol-9-yl)butyl)-2,2'-bipyridine-4,4'-dicarboxylate) were synthesized and their photophysical, electrochemical, as well as electroluminescent (EL) properties were studied. They display intense deep red phosphorescent emission centered at 660 nm and 658 nm, respectively, both in solution and in the solid state at room temperature. The peripheral carbazole in the complexes acts as an electrochemical coupling unit providing the ability to carry out electrochemical deposition (ED) and to form an ED film on an ITO electrode under a positive potential. Highly luminescent ED films are obtained under a carefully controlled ED process, and used as emitting layers in organic light-emitting diodes (OLEDs). The diodes gives out strong pure red emission and a luminous efficiency of 3.9 cd/A. These are the first electropolymerized phosphorescent OLEDs to be reported.