The coordination ability of the hexaphosphinoylated p-tert-butylcalix[6]arene toward actinides is established, as well as its good separation ability of the actinide ions and Th(IV) over trivalent rare earths such as La(III), Eu(III), and Y(III). Spectrophotometric titration of uranyl with in yields and for the 1:1 and 1:2 () 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 1 and 3 fulfill their just with , 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 (), 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 ligand to the uranyl ion is demonstrated to be relevant in compound 1 with . The uranyl complex emission reveals a biexponential decay with from 210 to 220 μs and from 490 to 650 μs for compounds 1 and 3, respectively. The liquid-liquid extraction results demonstrate the good extraction capability of toward actinides but not for rare earths at room temperature. The extracted species keeps the 1(cation)/1(calixarene) ratio for the , , and ions. A good capacity of toward ions using aqueous phase 2 containing even up to 0.3 M thorium nitrate and an organic phase of in chloroform is found. The spectroscopic properties of the isolated uranyl complexes and the extraction studies reveal a uranophilic nature of . The molecular modeling results are in good agreement with the experimental findings.
Anne-Sophie Chauvin, Julien Alexandre Andres
Christian Ludwig, Rudolf Paul Wilhelm Jozef Struis, Ajay Bhagwan Patil, Mohamed Tarik