Theoretical study on the electronic structures and phosphorescent properties of a series of iridium(III) complexes with N^C^N-coordinating terdentate ligands

The geometry structures, electronic structures, absorption, and phosphorescent properties of a series of iridium(III) complexes with the structure Ir(N^C^N)(N^C)Cl, (N^C^N represents a terdentate coordination with different substituent groups C₂H₅ (1), NH₂ (2), CH₃ (3), H (4), CN (5), NO₂ (6), and CF₃ (7), N^C is 2-phenylpyridine) have been investigated using the density functional theory and time-dependent density functional theory. Calculations of ionisation potential and electron affinity were used to evaluate the injection abilities of holes and electrons into these complexes. The lowest energy absorption wavelength calculated is in good agreement with the experimental value. The lowest energy emissions of complexes 1-7 are localised at 552, 559, 549, 517, 627, 788, and 574 nm, respectively, at CAM-B3LYP level. For complexes 1 and 3, the calculated results showed a lower ΔE_S1-T1 and larger ³MLCT contributions and higher μ_s1 values, which could result in the larger k_r value than those of other complexes. It is anticipated that the theoretical studies can provide useful information for designing and synthesising the candidated phosphorescent material for use in the organic light-emitting diodes.