title: Selectivity of calix[4]arene-bis(benzocrown-6) in the complexation and transport of francium ion.
abstract: It is shown for the first time that a representative member of the "cesium-selective" calix[4]arene-crown-6 family exhibits a high affinity for Fr+ ion. In the investigation, the transport of 221Fr+ and Cs+ ions by calix[4]arene-bis(benzocrown-6) from an aqueous sodium nitrate solution into the water-immiscible diluent 1,2-dichloroethane was measured and compared to address the question of selectivity of the calix-crown-6 cavity toward alkali metal ions of increasing size. Selective separation of 221Fr+ from its parent 225Ac and from the matrix Na+ ions was demonstrated. Higher distribution ratios were obtained than those for the Cs+ ion. The extraction equilibria were determined for the case of the Cs+ ion, and the same equilibria were shown to be applicable to the case of Fr+ with inclusion of additional competitive effects.
authors.affiliation: Division of Chemical Sciences, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6119, USA.
authors.forename: Tamara J
authors.initials: TJ
authors.lastname: Haverlock
authors.forename: Saed
authors.initials: S
authors.lastname: Mirzadeh
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Moyer