Theoretical study on photophysical properties of cyclometalated cationic iridium(III) complexes containing dipyrido[3,2-f:2′,3′-h]quinoxaline ligand

We report a theoretical analysis of a family of cyclometalated cationic iridium(III) complexes: [Ir(C^N)2(N^N)]+ [N^N = dipyrido[3,2-f:2′,3′-h]quinoxaline(dpq), HC^N = 1-phenylpyrazole(Hppz) (1); HC^N = 7,8-benzoquinoline(Hbzq) (2); HC^N = 2-phenylquinoline(Hpq) (3); HC^N = 1-(2,4-diflourophenyl) pyrazole(Hdfppz) (4), HC^N = 1-(2,4-dimethylphenyl) pyrazole(Hdmppz) (5), HC^N = 1-(2,4-diflourophenyl)-1,2,4-triazole(Hdfptz) (6)] by using density functional theory (DFT) method to investigate their optoelectronic properties and understand the phosphorescent efficiency mechanism. Complexes 1–3 exhibit green to yellow luminescence. The different quantum efficiencies of 1–3 in methanol (MeOH), acetonitrile (CH3CN), and dichloromethane (CH2Cl2) solvents have been explained by calculated results. Complexes 4 and 5 show different trend in the absorption and emission spectra comparing with 1 due to the added different substituent on the phenyl of ppzH. The emission wavelength of the assumed complex 6 bearing the triazole in C^N ligand is blue-shifted to the blue region. We suggest complex 6 might be a potential candidate as blue-emitting material.