Functional Polypyridine Co Complex as an Efficient Catalyst for Photo‐Induced Water Oxidation

Abstract

A novel mononuclear cobalt complex 1 was synthesized by treatment of CoCl 2 •6H 2 O with a COOMe functionalized TPA ligand (TPA＝tris(2-pyridylmethyl)amine). In a basic borate buffer, 1 acts as an efficient catalyst for water oxidation, which is confirmed by an extinct catalytic oxidant wave in electrochemistry. Visible light-driven water oxidation has been achieved by 1 with a TON of 127.7 and a TOF of 3.8 s 1 respectively in a homogeneous system. In comparison to the reference RC with naked TPA, the higher efficiency of 1 evidences COOMe on ligand can improve the catalytic efficiency, leading to an effective pathway towards construction of a robust and stable artificial photosynthesis system.

Molecular and heterogeneous water oxidation catalysts: recent progress and joint perspectives

“…For example, for the Fe-and Co-based mononuclear WOCs 6, 11, and 12, it was concluded that substituents with higher electronegativity favored higher catalytic activity. [74][75][76] Instead, this positive promotion was supported with electron-donating ligands for Ni-based mononuclear WOC 15, 77 which is consistent with the observations for the axial ligand R (R designates pyridine and its derivatives) on WOC 9. 52 Nevertheless, it has been widely proposed that the activity promotion originates from a lower energy barrier for O-O bond formation.…”

Bio-Inspired Molecular Catalysts for Water Oxidation

“…Complex 105, [Co(PY5OH)(Cl)] + , was inspired by studies of complex 104 and features free hydroxy groups (in lieu of methoxy), which allows for further functionalization [175,176]. [179]. In comparison, complex 107 with non-functionalized TPA showed reduced activity by roughly an order of magnitude (TON of 12.6 and TOF 0.3 s −1 ); the high efficiency of complex 106 was attributed to the moderately more electron-withdrawing nature of COOMefunctionalized TPA (or steric considerations), thought to increase the stability of 106 by precluding self-oxidation and dimerization [179].…”

“…[179]. In comparison, complex 107 with non-functionalized TPA showed reduced activity by roughly an order of magnitude (TON of 12.6 and TOF 0.3 s −1 ); the high efficiency of complex 106 was attributed to the moderately more electron-withdrawing nature of COOMefunctionalized TPA (or steric considerations), thought to increase the stability of 106 by precluding self-oxidation and dimerization [179]. Interestingly, both complexes 106 and 107 have chloride ligands, which enhanced the catalytic activity relative to complex 104.…”