[01.2] PHYSICAL CHEMISTRY CHEMICAL PHYSICS 3: 1317-1325 2001
Lanthanide cation binding to a phosphoryl-calixarene: the importance of solvent and counterions investigated by molecular dynamics and quantum mechanical simulations
Marc Baaden, Michel Burgard 1, Christian Boehme 2, Georges Wipff2,*
Molecular dynamics simulations on the 1:1 M3+ lanthanide (La3+, Eu3+ and Yb3+) inclusion? complex of a t-butyl-calixarene L substituted at the narrow rim by four CH2-P(O)Ph2 arms demonstrate the role of hydration and counterions on the cation binding mode and shielding. In dry chloroform and in the absence of counterions, the cation is endo?, fully encapsulated within the pseudo-cavity delineated by the four phosphoryl arms and the four phenolic oxygens. This endo? bidentate binding mode is supported by full ab initio quantum mechanical optimization of the calixarene M3+ complexes. In biphasic solution, the complexes are shown to be surface active and to adsorb at an oil?/water interface with the cationic site pointing towards water and the hydrophobic t-butyl groups in oil?. The cation is not encapsulated, but adopts an exo ? position, coordinated to the four PO oxygens of L, to water molecules, and to counterions. This complex is too hydrophilic to be extracted from the interface to an organic phase. The unexpected binding mode has important implications concerning the mechanism of liquid-liquid ion extraction and the microscopic state of the extracted complex in the organic phase.
|Article 2001.2 (PCCP 3, 1317)|
Correspondence should be addressed to Prof. G. Wipff.
- Univ Strasbourg 1, Lab Chim Minerale & Chim Phys Ind, ECPM, UMR CNRS 7512, F-67087 Strasbourg, France.
- Univ Strasbourg 1, CNRS, UMR 7551, Inst Chim, 4 Rue B Pascal, F-67000 Strasbourg, France.
To the memory of our colleague Jean-Pierre Brunette.
3 times cited on 2/2/2005 (Ref. ISI Web Of Science)