A novel Re(I) complex for electroluminescence application: synthesis, theoretical studies, photophysical and electroluminescent properties

In this paper, we report a novel phosphorescent Re(I) complex of Re(CO)₃(ETCP)Br, where ETCP=1-ethyl-2-naphthalen -1-yl-1H-1,3,7,8-tetraaza-cyclopental]phenanthrene, including its photophysical properties, geometric/electronic structures, electrochemical and thermal properties. Experimental data suggest that Re(CO)₃(ETCP)Br is a promising yellow emitter peaking at 540--nm with short excited state lifetime of ∼0.06 μs. Re(I) center localizes in a distorted octahedral field in Re(CO)₃(ETCP)Br and the emissive state of Re(CO)₃(ETCP)Br has metal-to-ligand-charge-transfer character, leading to the room-temperature phosphorescence. Further analysis reveals that Re(CO)₃(ETCP)Br has HOMO and LUMO energy levels at −6.03 V and −3.56 V, respectively, as well as its high thermal decomposition temperature of 377 °C. Using Re(CO)₃(ETCP)Br as a dopant, an electroluminescence peaking at 565-nm is realized, with a maximum luminance of 5900 cd/m² and a maximum current efficiency of 11.3 cd/A.