Improving the NLO response of bis-cyclometalated iridium(III) complexes by modifying ligands: A DFT study

Density functional theory (DFT) have been carried out to investigate the nine recently reported iridium (III) complexes which substituted various cyclometalated ligands (C<^>N) and aryl isocyanide ancillary ligands (CNAr). The aim of this paper is to study the substituents effect on geometrical structures, electronic and second-order nonlinear optical (NLO) properties, UV-vis absorption spectra. It is found that the first hyperpolarizabilities can be easily modulated by the introduction of different electron-withdrawing/donating ligands on C<^>N and CNAr. Complexes with 2-benzothienylpyidine (btp) C<^>N ligands or the substituents on CNAr are electron-withdrawing groups -NO2 possess larger first hyperpolarizabilities values compared to remaining complexes. Significantly, the changes of the first hyperpolarizability can be qualitatively explained by means of the charge transfer pattern. It is anticipative that the theoretical investigation of these iridium complexes will be helpful for designing high-performance and versatile NLO materials. (C) 2018 Elsevier B.V. All rights reserved.