title: Amavadin and Homologues as Mediators of Water Oxidation.
abstract: The vanadium(IV) N-hydroxyiminodicarboxylate complexes [V(HIDPA)2](2-) and [V(HIDA)2](2-), close models of the amavadin (a natural product from Amanita fungi lacking the V=O group but exhibiting a rare NO-bound oxyiminate moiety), are shown to be the first recognized complexes of the early transition metals (up to periodic Group 7) that mediate the oxidation of water. The reactions were analyzed by visible spectrophotometry, mass spectrometry, and measurement of evolved dioxygen using Ce(4+) as sacrificial oxidant. A mechanism proposed on the basis of DFT calculations involves the reversible oxidation to the mononuclear V(V)-{OṄ<} center, where the redox active oxyimino group plays a key role and metal oxidation state variation is only one unit. The more similar model of the metallobiomolecule, [V(HIDPA)2](2-), displays a lower oxidation rate than [V(HIDA)2](2-) but does not undergo appreciable degradation, in contrast to the latter.
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001, Lisboa, Portugal.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Domarus
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001, Lisboa, Portugal.
authors.forename: Maxim L
authors.identifier: http://orcid.org/0000-0001-5729-6189
authors.initials: ML
authors.lastname: Kuznetsov
authors.affiliation: Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066, Bobadela LRS, Portugal.
authors.forename: Joaquim
authors.identifier: http://orcid.org/0000-0001-7580-057X
authors.initials: J
authors.lastname: Marçalo
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001, Lisboa, Portugal. pombeiro@tecnico.ulisboa.pt.
authors.forename: Armando J L
authors.identifier: http://orcid.org/0000-0001-8323-888X
authors.initials: AJ
authors.lastname: Pombeiro
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001, Lisboa, Portugal. pcd1950@tecnico.ulisboa.pt.
authors.forename: José Armando L
authors.identifier: http://orcid.org/0000-0001-9708-1043
authors.initials: JA
authors.lastname: da Silva
keywords: N-hydroxyiminodicarboxylate complexes; amavadin; ligand effects; vanadium; water oxidation