title: A Uranyl Peroxide Dimer in the Gas Phase.
abstract: The gas-phase uranyl peroxide dimer, [(UO2)2(O2)(L)2]2+where L = 2,2'-trifluoroethylazanediyl)bis(N,N'-dimethylacetamide), was synthesized by electrospray ionization of a solution of UO22+and L. Collision-induced dissociation of this dimer resulted in endothermic O atom elimination to give [(UO2)2(O)(L)2]2+, which was found to spontaneously react with water via exothermic hydrolytic chemisorption to yield [(UO2)2(OH)2(L)2]2+. Density functional theory computations of the energies for the gas-phase reactions are in accord with observations. The structures of the observed uranyl dimer were computed, with that of the peroxide of particular interest, as a basis to evaluate the formation of condensed phase uranyl peroxides with bent structures. The computed dihedral angle in [(UO2)2(O2)(L)2]2+is 145°, indicating a substantial deviation from the planar structure with a dihedral angle of 180°. Energies needed to induce bending in the most elementary gas-phase uranyl peroxide complex, [(UO2)2(O2)]2+, were computed. It was found that bending from the lowest-energy planar structure to dihedral angles up to 140° required energies of <10 kJ/mol. The gas-phase results demonstrate the inherent stability of the uranyl peroxide moiety and support the notion that the uranyl-peroxide-uranyl structural unit is intrinsically planar, with only minor energy perturbations needed to form the bent structures found in studtite and uranyl peroxide nanostructures.
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Phuong D
authors.initials: PD
authors.lastname: Dau
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Phuong V
authors.initials: PV
authors.lastname: Dau
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Linfeng
authors.initials: L
authors.lastname: Rao
authors.affiliation: European Commission, Joint Research Centre, P.O. Box 2340, 76125 Karlsruhe, Germany.
authors.forename: Attila
authors.identifier: http://orcid.org/0000-0001-8169-3547
authors.initials: A
authors.lastname: Kovács
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: John K
authors.identifier: http://orcid.org/0000-0003-2107-5418
authors.initials: JK
authors.lastname: Gibson