Photolytic water oxidation catalyzed by a molecular carbene iridium complex
By Petronilho, Ana; Rahman, Mahfujur; Woods, James A.; Al-Sayyed, Haris; Muller-Bunz, Helge; Don MacElroy, J. M.; Bernhard, Stefan & Albrecht, Martin
Published in Dalton Trans.
The Royal Society of Chemistry
2012
Abstract
The complex IrCl2(Cp*)(trz) (trz = triazolylidene), 2, was prepared from readily available 1, 3-dimethyl-4-phenyl-1, 2, 3-triazolium salt. Under basic conditions, the C-bound phenyl group readily cyclometalates, while under acidic conditions, cyclometalation is reversed. The sensitivity of the Caryl-Ir bond but not the Ctrz-Ir bond towards acidolysis provided a basis for using 2 as a catalyst in CeIV-mediated water oxidation. The catalytic activity is characterized by a robust catalytic cycle, affording excellent turnover numbers (TON > 20 000). Under cerium-free conditions and in the presence of hematite as a photoelectrode, light-induced activity was observed. The photoelectrochemical reaction is strongly pH-dependent, which requires pH adjustments when running multiple cycle experiments to regenerate the catalytic activity. Analogous chelating complexes display better stability and higher catalytic activity than the monodentate complex 2.