A phosphorescent rhenium emitter with minimal fluorescent component induced by heavy atom: synthetic procedure,...

In this paper, a Br-containing diamine ligand of 2-(4-bromophenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (referred to as BrPO) and its corresponding Re(I) complex of Re(CO)3(BrPO)Br are synthesized and studied in detail, including molecular structure, photophysical feature, thermal stability and electrochemical property. Experimental data suggest that Re(CO)3(BrPO)Br takes a octahedral coordination environment, and the π-π attraction between BrPO ligands makes complex molecules take a highly-ordered arrangement. Re(CO)3(BrPO)Br is found to be a yellow emitter peaking at 565 nm with emission yield of 0.11 and excited state lifetime of 4.21 μs. The emission comes from triplet excited state of ML&LLCT, where ML&LLCT means metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer as suggested by theoretical calculation. The fluorescent component in the emissive center is minimized by the heavy-atom turbulence effect. Re(CO)3(BrPO)Br owns a high thermal decomposition of 280°C, with HOMO of -5.45eV and LUMO of -3.12 eV. The optimal electroluminescent device using Re(CO)3(BrPO)Br as the emitting dopant gives a maximum brightness of 5906 cd/m(2) and a maximum current efficiency of 5.6 cd/A.