Syntheses, structures, and electrochemistry of a dinuclear compound and a mononuclear–mononuclear cocrystalline compound of uranyl(VI)

Abstract

AbstractSyntheses, structures, and electrochemistry of a dialkoxo‐bridged diuranyl(VI) compound [(UO2)2(L1)2(dimethylformamide)2] (1) and a mononuclear–mononuclear cocrystalline compound [(UO2)(L2)(H2O)⊂(H2O)]·[(UO2)(L2)(H2O)] (2) derived from Schiff base ligands are reported (H2L1 = Schiff base ligand obtained on condensation of 3‐ethoxysalicylaldehyde with 2‐aminoethanol; H2L2 = N,N ′‐o ‐phenylenebis(3‐ethoxysalicylaldimine)). The compounds 1 and 2 crystallize in the space groups P 21/c and P 1, respectively. Compound 1 is a dialkoxo‐bridged dinuclear compound of uranium(VI) containing two deprotonated ligands, [L]2–, two dimethylformamide (dmf) molecules and two UO22+ centers. Three C–H···O type hydrogen bonds involving one uranyl oxygen, two dmf hydrogens, and the imine hydrogen link the dinuclear units into a two‐dimensional network. Compound 2 is a cocrystal of two mononuclear units, [(UO2)(L2)(H2O)⊂(H2O)] (unit 1) and [(UO2)(L2)(H2O)] (unit 2). In unit 1, the non‐coordinated water molecule forms hydrogen bonds with oxygens of phenoxo, ethoxy, and coordinated water molecules resulting in the formation of an inclusion product. The overall supramolecular structure of compound 2 is one‐dimensional and consists of interlinked self‐assembled dimeric unit of unit 1 and unit 2. Cyclic voltammetric measurements reveal that the uranium(VI) center in [(UO2)2(L1)2(dimethylformamide)2] (1) is reduced quasireversibly at E1/2 = –773 mV with ΔEP = 121 mV, while the metal center in [(UO2)(L2)(H2O)⊂(H2O)]·[(UO2)(L2)(H2O)] (2) is reduced reversibly with E1/2 = –765 mV with ΔEP = 68 mV. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)