A rhenium complex with diamine ligand containing oxadiazole group and fluorine atom: Synthesis, characterization, photoluminescence and electroluminescence performances

In this paper, a diamine ligand of 2-(4-fluorophenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (FPYOZ), which owned both enlarged conjugation chain with electron-pulling group and fluorine atom, was synthesized. Its corresponding Re(I) complex was also synthesized and studied in detail, including single crystal analysis, electronic structure, photophysical performance, thermal stability and electrochemical property. Single crystal analysis suggested that there was a coordination ability difference between the N atom from pyridine ring and the one from oxadiazole moiety. Theoretical calculation on the complex suggested that the onset electronic transition owned a mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer. Upon photoexcitation of 375 nm, this complex showed a yellow emission peaking at 537 nm with excited state lifetime of 8.35 μs. Cyclic voltammetry result suggested that this complex owned HOMO and LUMO energy levels of −5.37 eV and −3.04 eV. The decomposition temperature of this complex was as high as 300 °C, as revealed by thermogravimetric analysis data. The optimal electroluminescence device using this complex as the emitting dopant showed an electroluminescence peaking at 562 nm, with a maximum luminance of 6250 cd/m2 and a maximum current efficiency of 7.3 cd/A.

► A diamine ligand with large conjugation chain and F atom was synthesized. ► Photophysical performance of its Re(I) complex was fully characterized and studied. ► This complex owned good thermal stability and well-suited levels for EL application. ► A maximum brightness of 6250 cd/m2 was achieved, with maximum efficiency of 7.3 cd/A.