Photoluminescence and electroluminescence of cationic PtAu2 heterotrinuclear complexes with aromatic acetylides.

Cationic PtAu2 heterotrinuclear complexes [PtAu2(dpmp)2(C[triple bond, length as m-dash]CR)2]2+ (dpmp = bis(diphenylphosphinomethyl)phenylphosphine, R = aryl) of aromatic acetylides were prepared. The PtAu2 structures are supported through doubly bridging dpmp and stabilized by a significant Pt-Au interaction. They are highly phosphorescent in fluid CH2Cl2 solution (Φem = 23.5%-78.9%), the solid state (Φem = 15.4%-70.2%), the PMMA film (Φem = 39.9%-71.7%) and the doping film of 61% TCTA : 31% OXD-7 : 8% PtAu2 complex (Φem = 16.9%-67.9%). The phosphorescence arises mainly from 3[π (C[triple bond, length as m-dash]CR) → π* (dpmp)] 3LLCT and 3[π (C[triple bond, length as m-dash]CR) → s/p (PtAu2)] 3LMCT triplet excited states for carbazole-acetylide complexes, whereas other complexes display a 3LLCT character mixed with noticeable PtAu2 centered 3[d → s/p] parentage. Utilizing a mixed host composed of hole-transporting TCTA and electron-transporting OXD-7 doped with 8% PtAu2 species as a light-emitting layer and CuSCN as a hole-transporting layer through an orthogonal solution process, the devices exhibit highly efficient electrophosphorescence with the highest current efficiency (CEmax) of 51.7 cd A-1 and external quantum efficiency (EQEmax) of 14.5%. The efficiency roll-off is small in the practical brightness range of 500-5000 cd m-2. The PtAu2 complexes with carbazole-acetylides display a higher electroluminescence efficiency ascribed to their better hole-transporting character as well as more facile energy transfer from mixed host materials.