Jean-Claude Bunzli - Uranyl complexes formed with a para-t-butylcalix[4]arene bearing phosphinoyl pendant arms on the lower rim. Solid and solution studies

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      Ramirez,F.D., Varbanov,S., Bunzli,J.C.G., Rivas-Silva,J.F.,   Ocana-Bribiesca,M.A., Cortes-Jacome,M.A., Toledo-Antonio,J.A.   Radiochimica Acta 2012 100 (6)   359-369

      Abstract: The current interest in functionalized   calixarenes with phosphorylated pendant arms resides in their   coordination ability towards f elements and capability towards   actinide/rare earth separation. Uranyl cation forms 1: 1 and 1: 2   (M : L) complexes with a tetra-phosphinoylated   p-tert-butylcalix[4]arene, B(4)bL(4):   UO2(NO3)(2)(B(4)bL(4))(n)center dot xH(2)O (n = 1, x = 2, 1; n =   2, x = 6, 2). Spectroscopic data point to the inner coordination   sphere of 1 containing one monodentate nitrate anion, one water   molecule and the four phosphinoylated arms bound to UO22+ while   in 2, uranyl is only coordinated to calixarene ligands. In both   cases the U(VI) ion is 8-coordinate. Uranyl complexes display   enhanced metal-centred luminescence due to energy transfer from   the calixarene ligands; the luminescence decays are   bi-exponential with associated lifetimes in the ranges 220 mu s   < tau(s) <250 mu s and 630 mu s < tau(L) < 640 mu s,   pointing to the presence of two species with differently   coordinated calixarene, as substantiated by a XPS study of   U(4f(5/2, 7/2)), O(1s) and P(2p) levels on solid state samples.   The extraction study of UO22+ cation and trivalent rare-earth (Y,   La, Eu) ions from acidic nitrate media by B(4)bL(4) in chloroform   shows the uranyl cation being much more extracted than rare   earths

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