title: A Mononuclear Uranium(IV) Single-Molecule Magnet with an Azobenzene Radical Ligand.
abstract: A tetravalent uranium compound with a radical azobenzene ligand, namely, [{(SiMe2 NPh)3 -tacn}U(IV) (η(2) -N2 Ph2 (.) )] (2), was obtained by one-electron reduction of azobenzene by the trivalent uranium compound [U(III) {(SiMe2 NPh)3 -tacn}] (1). Compound 2 was characterized by single-crystal X-ray diffraction and (1) H NMR, IR, and UV/Vis/NIR spectroscopy. The magnetic properties of 2 and precursor 1 were studied by static magnetization and ac susceptibility measurements, which for the former revealed single-molecule magnet behaviour for the first time in a mononuclear U(IV) compound, whereas trivalent uranium compound 1 does not exhibit slow relaxation of the magnetization at low temperatures. A first approximation to the magnetic behaviour of these compounds was attempted by combining an effective electrostatic model with a phenomenological approach using the full single-ion Hamiltonian.
authors.affiliation: C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS (Portugal).
authors.forename: Maria A
authors.initials: MA
authors.lastname: Antunes
authors.affiliation: C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS (Portugal).
authors.forename: Joana T
authors.initials: JT
authors.lastname: Coutinho
authors.affiliation: C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS (Portugal).
authors.forename: Isabel C
authors.initials: IC
authors.lastname: Santos
authors.affiliation: C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS (Portugal).
authors.forename: Joaquim
authors.initials: J
authors.lastname: Marçalo
authors.affiliation: C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS (Portugal).
authors.forename: Manuel
authors.initials: M
authors.lastname: Almeida
authors.affiliation: Instituto de Ciencia Molecular, Universitat de València, C/Catedrático José Beltrán 2, 46980 Paterna (Spain).
authors.forename: José J
authors.initials: JJ
authors.lastname: Baldoví
authors.affiliation: C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS (Portugal). lpereira@ctn.ist.utl.pt.
authors.forename: Laura C J
authors.initials: LC
authors.lastname: Pereira
authors.affiliation: Instituto de Ciencia Molecular, Universitat de València, C/Catedrático José Beltrán 2, 46980 Paterna (Spain). alejandro.gaita@uv.es.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Gaita-Ariño
authors.affiliation: Instituto de Ciencia Molecular, Universitat de València, C/Catedrático José Beltrán 2, 46980 Paterna (Spain). eugenio.coronado@uv.es.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Coronado
keywords: N ligands; azo compounds; magnetic properties; radicals; uranium