Theoretical study of geometric structures and electronic absorption spectra of Iridium(III) complexes based on 2-phenyl-5-nitropyridyl with different ancillary ligands

Abstract

In this paper, the influence of different ancillary ligands on geometric structures, frontier molecular orbitals character, gap energy and electronic absorption spectra of [Ir(5-NO2-ppy)2(PPh3)(L)] (L=Cl−, NCO−, NCS− and N−3) has been theoretically studied by density functional theory and time-dependent density functional theory calculations with B3LYP and PBE0 hybrid functionals. Calculated geometric parameters of studied complexes are in good agreement with the available experimental values. The theoretical absorption spectra reproduce the main properties of the experimental spectra. Both energy gaps and absorption spectra depend on the composition of HOMO Orbital, π-donor orbitals reduce the energy gaps and red shift the absorption spectra while π-acceptor orbitals increase the energy gaps and blue shift the absorption spectra. All the spectra are characterized by mixed MLCT/LLCT states in the visible energy domain.