Pius Adelani - Comparison of Thorium(IV) and Uranium(VI) Carboxyphosphonates

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      Abstract:

      The hydrothermal reactions of thorium nitrate and uranyl acetate   with carboxyphenylphosphonic acid and HF result in the formation   of   ThF2(PO3C6H4CO2H)   and   UO2(PO3HC6H4CO2H)2·2H2O,   respectively.   ThF2(PO3C6H4CO2H)   adopts a pillared structure constructed from thorium oxyfluoride   layers built from [ThO4F4] units that are   bridged by carboxyphenylphosphonate to yield a three-dimensional   network.   UO2(PO3HC6H4CO2H)2·2H2O   forms one-dimensional chains of UO6 tetragonal   bipyramids that are bridged by the phosphonate moiety of the   ligand. The carboxylate portion of the structure links the chains   together into layers via a hydrogen-bonding network. The higher   effective charge and more isotropic coordination of the Th(IV)   centers versus the uranium centers contained within uranyl   cations allow for coordination by the protonated carboxylate   portions of the ligands to the thorium cations, which does not   occur with uranium in carboxyphosphonates.   UO2(PO3HC6H4CO2H)2·2H2O   displays vibronically coupled fluorescence and the potential for   energy transfer from the ligand to the charge-transfer bands of   the uranyl cations. The main fluorescence by the ligand is   quenched in   ThF2(PO3C6H4CO2H)

      Address (URL): http://pubs.acs.org/doi/full/10.1021/ic1006132