Jean-Claude Bunzli - Physicochemical properties and theoretical modeling of actinide complexes with a para-tert-butylcalix[6]arene bearing phosphinoyl pendants. Extraction capability of the calixarene toward f elements

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      Ramirez,F.D., Varbanov,S., Padilla,J., Bunzli,J.C.G. Journal   of Physical Chemistry B 2008 112  (35) 10976-4

      Abstract: The coordination ability of the   hexaphosphinoylated p-tert-butylcalix[6]arene B(6)bL(6) toward   actinides is established, as well as its good separation ability   of the actinide ions UO(2)(2+) and Th(IV) over trivalent rare   earths such as La(III), Eu(III), and Y(III). Spectrophotometric   titration of uranyl with B(6)bL(6) in CH(3)CN yields log   beta(11)= 7.1 and log beta(12) = 12.5 for the 1: 1 and 1:2   (UO(2)(2+)/B(6)bL(6)) species, respectively. Actinide complexes   with 1: 1 and 1:2 (M/L) stoichiometries are isolated and   characterized by elemental analysis, IR, and UV-vis. Compounds I   and 3 fulfill their CN = 8 just with B6bL6, while compounds 2 and   4 require coordinated nitrates and/or water molecules. The   luminescence spectra of the uranyl complexes and the parameters   such as FWMH, vibronic spacing (v(sp)), and the U-O bond length,   as well as the luminescence lifetimes, permit the understanding   of the coordination chemistry of these actinide calixarene   complexes. Energy transfer from the B(6)bL(6) ligand to the   uranyl ion is demonstrated to be relevant in compound 1 with   Q(abs) = 2.0%. The uranyl complex emission reveals a   biexponential decay with tau(s) from 210 to 220 mu s and tau(L)   from 490 to 650 mu s for compounds 1 and 3, respectively. The   liquid-liquid extraction results demonstrate the good extraction   capability of B(6)bL(6) toward actinides but not for rare earths   at room temperature. The extracted species keeps the I   (cation)/1(calixarene) ratio for the UO(2)(2+), Th(4+), and   Eu(3+) ions. A good capacity of B(6)bL(6) 6 toward Th(4+) ions   using aqueous phase 2 containing even up to 0.3 M thorium nitrate   and an organic phase of 2.47 x 10(-4) M B(6)bL(6) in chloroform   is found. The spectroscopic properties of the isolated uranyl   complexes and the extraction studies reveal a uranophilic nature   of B(6)bL(6). The molecular modeling results are in good   agreement with the experimental findings

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