A Water‐Soluble Copper–Polypyridine Complex as a Homogeneous Catalyst for both Photo‐Induced and Electrocatalytic O₂ Evolution

Abstract

The water-soluble polypyridine copper complex [Cu(F3TPA)(ClO4)2] [1; F3TPA=tris(2-fluoro-6-pyridylmethyl)amine] catalyzes water oxidation in a pH 8.5 borate buffer at a relatively low overpotential of 610 mV. Assisted by photosensitizer and an electron acceptor, 1 also exhibits activity as a homogeneous catalyst for photo-induced O2 evolution with a maximum turnover frequency (TOF) of (1.58 ± 0.03) × 10(-1) s(-1) and a maximum turnover number (TON) of 11.61 ± 0.23. In comparison, the reference [Cu(TPA)(ClO4)2] [TPA=tris(2-pyridylmethyl)amine] displayed almost no activity under either set of conditions, implying the crucial role of the ligand in determining the behavior of the catalyst. Experimental evidence indicate the molecular catalytic nature of 1, leading to a potentially practical strategy to apply the copper complex in a photoelectrochemical device for water oxidation.

A Bio‐inspired Cu4O4 Cubane: Effective Molecular Catalysts for Electrocatalytic Water Oxidation in Aqueous Solution

“…Despite not fully elucidating these factors, there have been numerous advances in molecular catalyst design for water oxidation. [11][12][13] Their superior biomimetic reactivity [14] with oxygen, and the unique covalent metal-oxo bonding in Cu 2 (m-O) 2 core are expected to be advantage for oxygen evolution. [10] Owing to inexpensive and easily accessible to different oxidation state,c opper-based molecular water oxidation catalysts have been documented with the focus on mono-and bi-nuclear copper complexes.…”

“…Recrystallization of [(L Gly -Cu) 4 ] from acetonitrile/water solution gave rise to dark green blockshaped crystals.T he X-ray crystal structure revealed that [(L Gly -Cu) 4 ]( L Gly :3 -methoxy-salicylidene-glycine) featured au nique tetrameric cubane-like structure.A ss hown in Figure 1, each Cu atom is coordinated with one Na tom and five Oatoms.T aking Cu1 as arepresentative,the N1, O2, and O3 atoms from one horizontal ligand and the O2' atom from another vertical ligand are sited in the equatorial plane,while the O2'' and O1' atoms are arranged in an apical fashion. Thet urnover frequency (TOF) is determined to be 267 s À1 for [(L Gly -Cu) 4 ]at1.70 Vand 105 s À1 for [(L Glu -Cu) 4 ]at 1.56 V. Theexceptional catalytic efficiency, higher than those of mono-or binuclear ones (0.4-100 s À1 ) [11][12][13] enable us to believe that the Cu 4 O 4 cubane core is promising for the catalytic oxygen evolution. Indeed, the assynthesized cubane complexes ([(L Gly -Cu) 4 ]and [(L Glu -Cu) 4 ]) exhibit superior oxygen evolution ability in aqueous solution (pH 12).…”

“…[19] Thefitted slope is equal to ÀRT/anFand RT/(1Àa)nF for the cathodic peak (E p,c )and the anodic peak (E p,a ), where a (transfer coefficient) and n can be deduced as 0.5 and 2respectively (see details in the Supporting Information). [11][12][13] Thel inear scan voltammograms (LSVs) for [(L Gly -Cu) 4 ]a nd [(L Glu -Cu) 4 ]w ere further obtained at tindoped indium oxide (ITO) electrodes.T he greatly enhanced catalytic current suggested water oxidation occurrence (Supporting Information, Figure S9). Thep rofile of the differential pulse voltammetry (DPV) of [(L Gly -Cu) 4 ]w as dramatically changed by replacing the solvent from acetonitrile to PBS aqueous solution (pH 12; Supporting Information, Figures S7, S8).…”

“…Thep rofile of the differential pulse voltammetry (DPV) of [(L Gly -Cu) 4 ]w as dramatically changed by replacing the solvent from acetonitrile to PBS aqueous solution (pH 12; Supporting Information, Figures S7, S8). [11][12][13] To verify the oxygen evolution, controlled-potential electrolysis (CPE) of 0.25 mm [(L Gly -Cu) 4 ]i n0 .2 m PBS (pH 12.0) was performed in ag as-tight custom-designed cell at 1.50 Vw ith aI TO electrode (1.00 cm 2 ;S upporting Information, Figure S11). [11][12][13] Thel inear scan voltammograms (LSVs) for [(L Gly -Cu) 4 ]a nd [(L Glu -Cu) 4 ]w ere further obtained at tindoped indium oxide (ITO) electrodes.T he greatly enhanced catalytic current suggested water oxidation occurrence (Supporting Information, Figure S9).…”

Preparation and characterization of Cu (II) supported on poly(8‐hydroxyquinoline‐p‐styrene sulphonate) and its application as catalyst for the synthesis of hexahydroquinolines

“…Transition metal complexes are widely used to catalyze the organic reactions . Chelation reaction of polymers with metal ions provides useful properties depending on the structure of metal‐chelate, including high temperature and flame resistant, low leaching the metal ion to the reaction mixture, and recyclability of the metal loaded polymers .…”