Jean-Claude Bunzli - Lanthanide complexes with a p-tert-butylcalix[4]arene fitted with phosphinoyl pendant arms

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  Le Saulnier,L., Varbanov,S., Scopelliti,R., Elhabiri,M.,   Bunzli,J.C.G. Journal of the Chemical Society-Dalton   Transactions 1999 (22) 3919-3925

  Abstract: The lower-rim substituted   calix[4]arene,   5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(dimethylphosphinoylmethoxy)cal ix[4]arene   (L) has been synthesized and characterised by the single-crystal   structure of its acetonitrile adduct, L . 2MeCN (monoclinic,   space group P2(1)/c). The ligand adopts a cone conformation and a   Delta enantiomeric form with the four phosphinoyl arms in a delta   delta delta delta configuration. The cone conformation is   maintained in organic solution where L displays a time-averaged   C-4 symmetry. Trivalent lanthanum ions interact with L in   acetonitrile to yield both 1:1 (log beta (1);=11.4 +/- 1.5) and   1:2 (log beta(2)=19.6 +/- 1.8) complexes; two forms of the 1:1   complex are identified depending on the water content of the   solutions. A photophysical study of both the ligand- and   metal-centred luminescence of complexes of La, Eu and Tb points   to L having a moderate quantum yield (ca. 10%, ligand-centred   luminescence) and being a poor sensitiser of europium and terbium   ions. It confirms the presence of differently solvated 1:1 (and   1:2) complexes, depending on the solvent composition. The   lifetimes of the metal-centred luminescence of the unhydrated 1:1   and 1:2 complexes are long, in the range 1.4-2.4 ms for Eu and   1.7-7.3 ms for Tb, which indicates that the lanthanide(III) ions   are well encapsulated in the cavity formed by the donor groups of   the calix[4]arene molecule(s)

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