Synthesis, molecular and supramolecular structure, spectroscopy and electrochemistry of a dialkoxo-bridged diuranyl(VI) compound

The synthesis, molecular and supramolecular structure, spectroscopy and electrochemistry of a dialkoxo-bridged diuranyl(VI) compound [(UO2)(2)(L)(2)(dimethylformamide)(2)] (1) derived from the Schiff base ligand H2L, obtained on condensation of 3-methoxysalicylaldehyde with 2-aminoethanol, have been described. The compound has been characterized by IR, UV-Vis, NMR and mass spectra, as well as by single crystal X-ray structure determination. The title compound crystallizes in the monoclinic P2(1)/n space group with the following unit cell parameters a = 10.5713(2) angstrom, b = 11.9895(2) angstrom, c = 12.9372(2) angstrom, beta = 102.773(3)degrees and Z = 2. The structure of 1 reveals that it is a dialkoxo-bridged dinuclear compound of uranium(VI) containing two deprotonated ligands, [L](2-), two dimethylformamide (dmf) molecules and two UO22+ centers. The coordination geometry around the uranium(VI) center is distorted pentagonal bipyramidal; two uranyl oxygens occupy the axial positions, while the basal pentagonal plane is defined by a phenoxo oxygen, two bridging alkoxo oxygens, one imine nitrogen, and one dmf oxygen. Three C-H center dot center dot center dot O type hydrogen bonds involving one uranyl oxygen, two dmf hydrogens and,the imine hydrogen link the dinuclear units into a two-dimensional network. The ESI-MS spectrum of 1 in dimethylsulfoxide exhibits two peaks at m/z = 464.17 and 927.26, which are assignable to [(UO2)(2)L2H](+) (60%) and [(UO2)(2)LH](+) (100%) cations, respectively. Cyclic voltammetric measurements of I reveal that the uranium(VI) center is reduced quasireversibly at E-1/2 = -1112 mV with Delta E-p = 97 mV. (C) 2008 Elsevier Ltd. All rights reserved.