Visible Light-driven Hydrogen Production And Polymerization Using Triarylboron-functionalized Iridium(?) Complexes

The development of novel iridium(?)complexes has continued as an important area of research due to their highly tunable photophysical properties and versatile applications.In this report,three heteroleptic dimesitylboron-containing iridium(III)complexes,[Ir(p-B-ppy)2(N^N)]+(1-3;p-B-ppy=2-(4-dimesitylboryl-phenyl)-pyridine);N^N =dipyrido[3,2-a:2',3'-c]phenazine(dppz)for 1,dipyrido[3,2-d:2',3'-f]quinoxaline(dpq)for 2 and 1,10-phenanthroline(phen)for 3)were prepared and fully characterized electrochemically,photophysically,and computationally.Altering the conjugated length of N^N ligands allowed us to tailor the photophysical properties of these complexes,especially their luminescence wavelength,which can be adjusted from 583 nm to 631 nm in CH2Cl2.All three complexes were evaluated as visible-light-absorbing sensitizers for the photogeneration of hydrogen from water and as photocatalysts for the photopolymerization of methyl methacrylate(MMA).The results showed that all of them were active in both photochemical reactions.A high activity for the photosensitizer(PS,over 1158 turnover numbers(TONs)with 1)was observed,and the system generated hydrogen even after 20 h.Additionally,poly(methyl methacrylate)(PMMA)with a relatively narrow molecular weight distribution was obtained when an initiator(ethyl a-bromophenylacetate,EBP)was used.The living character of the photoinduced polymerization was confirmed on the basis of successful chain-extension experiments.