Visible‐Light‐Driven Hydrogen Production and Polymerization using Triarylboron‐Functionalized Iridium(III) Complexes

• Published in: Chemistry, an Asian journal Vol. 13; no. 13; pp. 1699 - 1709
• Main Authors: Yang, Ling‐Xia, Yang, Wan‐Fa, Yuan, Yong‐Jun, Su, Yi‐Bing, Zhou, Miao‐Miao, Liu, Xiao‐Le, Chen, Guang‐Hui, Chen, Xin, Yu, Zhen‐Tao, Zou, Zhi‐Gang
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 04.07.2018
• Subjects: Chemistry; Dichloromethane; hydrogen; Hydrogen production; Iridium; Iridium compounds; Molecular chains; photocatalysis; Photochemical reactions; Photopolymerization; Polymerization; Polymethyl methacrylate; sensitizers; iridium; polymerization; hydrogen; photocatalysis; sensitizers
• ISSN: 1861-4728; 1861-471X
• DOI: 10.1002/asia.201800455

The development of novel iridium(III) complexes has continued as an important area of research owing 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)]+ {p‐B‐ppy=2‐(4‐dimesitylborylphenyl)pyridine; N^N=dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz) (1), dipyrido[3,2‐d:2′,3′‐f]quinoxaline (dpq) (2), and 1,10‐phenanthroline (phen) (3)}, were prepared and fully characterized electrochemically, photophysically, and computationally. Altering the conjugated length of the N^N ligands allowed us to tailor the photophysical properties of these complexes, especially their luminescence wavelength, which could be adjusted from λ=583 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. The results showed that all of them were active in both photochemical reactions. High activity for the photosensitizer (over 1158 turnover numbers with 1) was observed, and the system generated hydrogen even after 20 h. Additionally, poly(methyl methacrylate) with a relatively narrow molecular‐weight distribution was obtained if an initiator (i.e., ethyl α‐bromophenylacetate) was used. The living character of the photoinduced polymerization was confirmed on the basis of successful chain‐extension experiments. Photo op: Three heteroleptic dimesitylboron (Mes2B)‐containing iridium(III) complexes are evaluated as visible‐light‐absorbing sensitizers for the photogeneration of hydrogen from water and as photocatalysts for the photopolymerization of methyl methacrylate (MMA) to poly(methyl methacrylate) (PMMA). WRC=water reduction catalyst, SR=sacrificial reductant, EBP=ethyl α‐bromophenylacetate, PS=photosensitizer.