Two Novel Schiff Base Manganese Complexes as Bifunctional Electrocatalysts for CO Reduction and Water Oxidation.

One mononuclear Mn(III) complex Mn(HO)(MeCN) () and one hetero-binuclear complex (CuMn(HO))(Cu)·CHOH () have been synthesized with the Schiff base ligand (H = N,N'-bis(3-methoxysalicylidene)-1,2-phenylenediamine). Single crystal X-ray structural analysis manifests that the Mn(III) ion in has an octahedral coordination structure, whereas the Mn(II) ion in possesses a trigonal bipyramidal configuration and the Cu(II) ion in is four-coordinated with a square-planar geometry. Electrochimerical catalytic investigation demonstrates that the two complexes can electrochemically catalyze water oxidation and CO reduction simultaneously. The coordination environments of the Mn(III), Mn(II), and Cu(II) ions in and were provided by the Schiff base ligand () and labile solvent molecules. The coordinately unsaturated environment of the Cu(II) center in can perfectly facilitate the catalytic performance of . Complexes and display that the over potentials for water oxidation are 728 mV and 216 mV, faradaic efficiencies (FEs) are 88% and 92%, respectively, as well as the turnover frequency (TOF) values for the catalytic reduction of CO to CO are 0.38 s at -1.65 V and 15.97 s at -1.60 V, respectively. Complex shows much better catalytic performance for both water oxidation and CO reduction than that of complex , which could be owing to a structural reason which is attributed to the synergistic catalytic action of the neighboring Mn(III) and Cu(II) active sites in . Complexes and are the first two compounds coordinated with Schiff base ligand for both water oxidation and CO reduction. The finding in this work can offer significant inspiration for the future development of electrocatalysis in this area.