Neutral Cyclometalated Ir(III) Complexes with Pyridylpyrrole Ligand for Photocatalytic Hydrogen Generation from Water

To explore structure-activity relationships with respect to lightharvesting behavior, a family of neutral iridium complexes [Ir(ppy)(2)(L-R)] 1-4 (where ppy = 2-phenylpyridine, and (N) over capN = 2-(1H-pyrrol-2-yl)pyridine and its functionalized derivatives) were designed and synthesized. The structural modifications in metal complexes are accomplished through the attributions of electron-donating CH3 in 2, OCH3 in 3, and electron-withdrawing CF3 in 4. The structural analysis displays that the pyridylpyrrole acts as one-negative charged bidentated ligand to chelate the iridium center. The electrochemical and photophysical properties of these complexes were systematically studied. The neutral 1-4 as well as the ionic structurally analogous [Ir(ppy)(2)(bpy)](PF6) (5) were utilized as PSs in photocatalytic hydrogen generation from water with [Co(bpy)(3)](PF6)(2) as catalyst and triethanolamine (TEOA) as electron sacrificial agent in the presence of salt LiCl. Complex 1 maintains activity for more than 144 h under irradiation, and the total turnover number is up to 1768. The electrochemical properties and the quenching reaction indicate the H-2 generation by neutral complexes 1-4 is involved exclusively in the oxidative quenching process.

Automated summary

A series of neutral iridium complexes were designed and synthesized to investigate the structure-activity relationships with respect to lightharvesting behavior, showing that structural modifications in metal complexes can affect their properties. The pyridylpyrrole ligand acts as a one-negative charged bidentated ligand to chelate the iridium center. Among them, complex 1 maintained activity for more than 144 hours under irradiation.