Chiral one- to three-dimensional uranyl-organic assemblies from (1R,3S)-(+)-camphoric acid

Four complexes were obtained from reaction of uranyl nitrate with (1R, 3S)-(+)-camphoric acid under solvo-/hydrothermal conditions with either acetonitrile or N-methyl-2-pyrrolidone (NMP) as the organic component. All complexes crystallize in chiral space groups and are enantiopure species. Complexes [(UO2)(4)(L)(3)(OH)(2)(H2O)(4)]center dot 3H(2)O (1) and [(UO2)(8)K-8(L)(12)(H2O)(12)]center dot H2O (2) were obtained in water-acetonitrile in the presence of LiOH or KOH in excess beyond or equal to that simply required to neutralize the acid, respectively. Whereas 1 is a 1D coordination polymer including hydroxide ions resulting from hydrolysis of the uranyl aqua-ion, 2 contains octanuclear uranyl camphorate cages analogous, but for their crystallographic symmetry, to those previously published; these cages are assembled into a 3D framework by bridging potassium ions. The two complexes obtained in water-NMP, [UO2(L)(NMP)] (3) and [(UO2)(2)Cu(L)(3)(NMP)(2)] (4), are devoid both of water molecules and any solvent-derived anions, and they crystallize as 2D assemblies. The sheets in 4, with a thickness of similar to 14 angstrom, display a central layer of copper(II) ions surrounded by two layers of uranyl ions. These and previous results suggest that solvo-/hydrothermal conditions using NMP provide a new means of avoiding the formation of uranyl-containing oligomeric or 1D polymeric hydrolysis products which are frequent and often unpredictable outcomes in the synthesis of uranyl-organic assemblies under aqueous conditions, especially in the presence of cosolvents which in themselves are susceptible to hydrolysis. The emission spectrum of compound 3 under excitation at 350 nm displays the usual vibronic fine structure in the similar to 460-600 nm range, while uranyl luminescence is quenched by Cu(II) cations in complex 4.