A Robust Visible-Light-Harvesting Cyclometalated Ir(III) Diimine Sensitizer for Homogeneous Photocatalytic Hydrogen Production

A cyclometalated Ir(III) diimine complex [Ir(NBI)2(phen)]PF6, NBI = 1,8-naphthalenebenzimidizole and phen = 1,10-phenanthroline, exhibits excellent photostability as a sensitizer in a three-component homogeneous aqueous photocatalytic hydrogen producing system. Here, [Co(dmgH)2(py)Cl] serves as the hydrogen evolving catalyst, and N,N-dimethyl-p-toluidine (DMT) serves as a sacrificial single electron donor. The [Ir(NBI)2(phen)]PF6 photosensitizer remained active over the course of 90 h of visible-light-induced (λex = 452 nm, 540 mW) H2 production photocatalysis, yielding a turnover number (H2/photosensitizer) of 575 occurring near neutral pH conditions. The proton source was verified as being derived from aqueous protons by detecting the headspace gas composition through mass spectrometry in experiments using deuterated water. Mercury metal was used as a selective poisoning test, intended to sequester any metal-based nanomaterial(s) produced in side reactions and provide evidence that the current photocata...