Investigation on the photophysical properties of a series of promising phosphorescent iridium (III) complexes with modified cyclometalating ligands

Abstract

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were applied to investigate the electronic structures and photophysical properties of a series of phosphorescent iridium (III) complexes, [(C∧N)2Ir(N∧N)]+(PF6)−, in which C∧N = 4-aryl-1-benzyl-1H-1, 2, 3-triazoles. Herein, aryl = phenyl, biphenyl, three-phenyl aromatic for complexes 1a, 2a, 3a (N∧N = 2, 2′-bipyridine) and aryl = 4′, 6′-difluorophenyl, 6′-fluoro-biphenyl, 6′-fluoro-three-phenyl aromatic for complexes 1b, 2b, 3b (N∧N = 4, 4′-di-tert-butyl-2, 2′-bipyridine), respectively. The geometric/electronic configurations, absorption/emission properties and phosphorescent performances have been outlined for each of the complexes. Based on the two simplifications presented in this paper and the available experimental data, the phosphorescent radiative rates for complexes 1a-3b were approximately obtained to be: 1.20 × 106 s−1, 1.68 × 105 s−1, 2.19 × 107 s−1, 3.85 × 106 s−1, 1.85 × 107 s−1 and 1.50 × 107 s−1, respectively. In view of the electroluminescent applications in OLED, our present research work is of great importance for the design and synthesis of organo-transition metal complexes with improved phosphorescent performances.