Synthesis and characterization of heteroleptic iridium(III) complexes incorporating 5-arylazo-8-hydroxyquinoline as coligands: DFT/TDDFT studies on the electronic structures and spectral properties

The orange coloured complexes of general formula [Ir(2-pypy)₂(hq)] have been prepared in exceptional yield by reaction of [Ir(2-pypy)₂(Cl)]₂ with Hhq under argon atmosphere in 1: 1 mixture of ethanol and dichloromethane in alkaline condition. Here hq- is deprotonated form of 5-phenylazo-8-hydroxyquinoline (Hhq¹), 5-(2-naphthylazo)-8-hydroxyquinoline (Hhq²) and 5-(2-fluorineazo)-8-hydroxyquinoline (Hhq³). The elemental analysis, ESI mass spectroscopic measurements, IR spectroscopy and ¹H NMR spectroscopy guarantee the formation of desired complexes. The ground and excited-state geometries, absorption, and phosphorescence properties of three Ir^III complexes were investigated by DFT and TDDFT methods. The natural transition orbital (NTO) and spin density analysis reveals the nature of excitations. The lowest lying triplet excited is connected with the ³IL and ³ML excited state is consistent with the emission like transition.