Second-order nonlinear optical response of phenyl-substituted cationic BIS-cyclometalated iridium(III) complexes: Effect of different position

In this paper, a series of cationic iridium complexes [(2-phenylpyridine) 2 (2,2'-bipyridine)Ir](+) which substituted phenyl on different ligands position have been systematically investigated by density functional theory (DFT) method. Significantly, the first hyperpolarizability beta(tot) values can be enhanced by introducing phenyl on 2-phenylpyridine ligands R-1 or R-2, whereas substituting phenyl on 2,2'-bipyridine ligands R-3 result in a decreasing beta(tot )values. The beta(tot) values exhibit obvious connection with the corresponding HOMO and LUMO energy gap. Furthermore, the time-dependent (TD) DFT calculations suggest that the enhanced beta(tot) values are related to obvious charge transfer from 2-phenylpyridine ligands to 2,2'-bipyridine ligands. The investigation of frequency-dependent first hyperpolarizability beta (-omega; omega, 0) and beta (-2 omega; omega) shown less dispersion effect at the low-frequency region for all of the studied complexes. Overall, tuning phenyl on the different ligands position can be seen as an effective strategy to modulate the second-order nonlinear optical response for these iridium complexes, which is benefit to theoretical and experimental further investigation.