Catalytic water oxidation mediated by copper‐triazolylpyridine complexes

Water oxidation reaction (WOR) is a rather sluggish process in the water splitting that hampers the extraction of hydrogen gas from water in a large scale. It is highly desirable to develop low‐cost WOR catalysts to increase the efficacy. Herein two Cu(II) complexes [Cu (DTEL) 2 ] n (ClO 4 ) 2n ( 1 ) and [Cu(DTE) 2 (ClO 4 ) 2 ] ( 2 ) of two triazolylpyridines, 1‐(2‐hydroxy)‐4‐(2‐pyridyl)1,2,3‐triazole (DTEL) and 1‐(2‐acetoxymethyl)‐4‐(2‐pyridyl)1,2,3‐triazole (DTE), have been synthesized and characterized. The X‐ray diffraction analysis revealed that the copper centers of 1 and 2 adopted the octahedral coordination geometry with four N atoms from two DTEL or DTE ligands in the equatorial plane. The two axial sites were weakly ligated by the hydroxyl group of DTEL or perchlorate. Both complexes 1 and 2 were homogenous molecular catalysts boosting the WOR in pH 9.0 phosphate buffer solution with the overpotentials being 568 and 478 mV, rate constants (k cat ) of 0.1 and 0.39 s −1 , and Faradaic efficiencies of 90% and 93%, respectively. The pendant substituent on the two triazolylpyridine ligands DTEL and DTE apparently influenced the catalysis. A mechanism for the catalytic WOR mediated by 1 and 2 was suggested on the basis of the experimental data. This work illustrated that triazolylpyridines were promising scaffolds for forming metal complexes working as WOR catalysts.