The influence of different substituent groups and Tr-conjugation degree on the optical and electronic properties of six Ir(III) complexes has been theoretically studied. The injection abilities of holes and electrons into these complexes have been evaluated with the ionization potential and electron affinity. The lowest energy absorption wavelengths calculated for these complexes are in good agreement with the available experimental values. The lowest energy emissions of these complexes are localized at 569, 584, 634, 554, 569, and 851 nm, respectively. The study could provide good information for designing the potential phosphorescent material for use in the organic light-emitting diodes. (C) 2015 Elsevier B.V. All rights reserved.