title: Redox Non-innocent Ligand Controls Water Oxidation Overpotential in a New Family of Mononuclear Cu-Based Efficient Catalysts.
abstract: A new family of tetra-anionic tetradentate amidate ligands, N1,N1'-(1,2-phenylene)bis(N2-methyloxalamide) (H4L1), and its derivatives containing electron-donating groups at the aromatic ring have been prepared and characterized, together with their corresponding anionic Cu(II) complexes, [(LY)Cu](2-). At pH 11.5, the latter undergoes a reversible metal-based III/II oxidation process at 0.56 V and a ligand-based pH-dependent electron-transfer process at 1.25 V, associated with a large electrocatalytic water oxidation wave (overpotential of 700 mV). Foot-of-the-wave analysis gives a catalytic rate constant of 3.6 s(-1) at pH 11.5 and 12 s(-1) at pH 12.5. As the electron-donating capacity at the aromatic ring increases, the overpotential is drastically reduced down to a record low of 170 mV. In addition, DFT calculations allow us to propose a complete catalytic cycle that uncovers an unprecedented pathway in which crucial O-O bond formation occurs in a two-step, one-electron process where the peroxo intermediate generated has no formal M-O bond but is strongly hydrogen bonded to the auxiliary ligand.
authors.affiliation: †Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 16, 43007 Tarragona, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Garrido-Barros
authors.affiliation: †Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 16, 43007 Tarragona, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Funes-Ardoiz
authors.affiliation: †Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 16, 43007 Tarragona, Spain.
authors.forename: Samuel
authors.initials: S
authors.lastname: Drouet
authors.affiliation: †Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 16, 43007 Tarragona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Benet-Buchholz
authors.affiliation: †Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 16, 43007 Tarragona, Spain.|‡Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
authors.forename: Feliu
authors.initials: F
authors.lastname: Maseras
authors.affiliation: †Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 16, 43007 Tarragona, Spain.|‡Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Llobet