Theoretical study of geometric, optical, nonlinear optical, UV–Vis spectra and phosphorescence properties of iridium(III) complexes based on 5-nitro-2-(2′,4′-difluorophenyl)pyridyl

In this work, we studied the structural, optical, nonlinear optical properties , absorption spectra and phosphorescence properties of four cyclometalated heteroleptic iridium complexes [Ir(dFNppy)2(PPh3)L] with dFNppy = 5-nitro-2-(2′,4′-difluorophenylpyridyl, PPh3 = triphenylphosphine, L = Cl− (1), NCS− (2), NCO− (3) and N3− (4) using DFT and TD-DFT methods. The electronic and geometrical structures of the S0 and T1 have been studied and compared. Experimental absorption bands were assigned on the basis of natural transition orbitales, and a good agreement with experience has been obtained. Phosphorescence wavelengths of the four complexes were calculated with vertical and adiabatic methods. Further, linear optical properties (mean polarizability $$\left\langle \alpha \right\rangle$$, anisotropy polarizability $$\left| \alpha \right|$$), the static first hyperpolarizabilities electric-field-induced second harmonic generation $$\beta_{//} \left( { - 2\omega ;\omega ,\omega } \right)$$ and the hyper-Rayleigh scattering (HRS) first hyperpolarizability $$\beta_{\text{HRS}} \left( { - 2\omega ;\omega ,\omega } \right)$$), and the depolarization ratio DR of these complexes are calculated by DFT with PBE0 functional in order to understand nonlinear optical properties. Higher polarizability $$(\alpha )$$ and first hyperpolarizabilities $$(\beta )$$ of these complexes are obtained. It is also observed an inverse correlation between the predicted β value and the HOMO–LUMO energy difference (Δe).