Long-lived cyclometallated iridium complexes: Synthesis, structure, DFT and photocatalytic aspects

Herein, we present synthesis, photophysical and photocatalytic aspects of four mononuclear luminescent iridium complexes ([1]+ - [4]+) incorporating cyclometallating benzimidazole-based (L1 and L2) and phenanthroline pyrazine-based (L3 - L5) ligands. Several analytical techniques were used for the characterization of the complexes. The structural elucidation of [2]+ and [3]+ using x-ray crystallography show a distorted Oh structure with nitrogen donors of cyclometallating ligands are in trans-direction. All the complexes are emitting in the orangered region and displayed moderately good quantum yield. The complexes have also shown moderately good luminescence lifetime (tau = 80-1900 ns) in different solvents. Importantly, the complex [3]+ exhibits comparative longer emission lifetime (tau = 1800 ns) in water at ambient condition. The complexes have shown moderately good photocatalytic efficacy towards azo dyes degradation in aqueous solution. The mechanistic investigation suggests that in the presence of light in aqueous medium the complexes induce the generation of (HO center dot/(O2 center dot ) species which is responsible for the photodecomposition of azo dyes.