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.

Graphical abstractThe electronic structures and optoelectronic properties of several cyclometalated cationic iridium(III) complexes: [Ir(C^N)2(N^N)]+ are investigated theoretically. The quantum efficiencies for all complexes have been explained by our calculated results. The assumed complex 6 might be a potential candidate for blue-emitting material.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We explained the different phosphorescent efficiency in different media. ► The emission of Ir(ppz)2(dpq) is red-shifted and blue-shifted by adding different substitutes ► Ir(dfptz)2(dpq) is a potential blue emitter.