Theoretical insight into the photophysical properties of six phosphorescent heteroleptic iridium(III) complexes with different monodentate ligands

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations have been employed to study the geometrical structures, electronic structures and photophysical properties of six heteroleptic iridium(III) complexes. The key aim is to investigate the effect of substituent groups with different conjugation length and different electron-donating/withdrawing ability on photophysical properties for these studied complexes. The lowest energy absorption wavelengths are located at 416 nm for 1, 426 nm for 2, 458 nm for 3, 470 nm for 4, 459 nm for 5 and 439 nm for 6, respectively. The lowest energy emissions of complexes 1 6 are localized at 559, 722, 890, 914, 648 and 768 nm, respectively, simulated in tetrahydrofuran medium at VSXC level. Furthermore, ionization potential (IP), electron affinities (EA) and reorganization energy (lambda(hole)(/electron)) have also been studied to evaluate the charge transfer and balance properties between hole and electron. It could be useful to design and synthesize potential phosphorescent organic light-emitting diodes (OLEDs) materials. (C) 2018 Elsevier Ltd. All rights reserved.