title: Rapid metal ions shuttling through 1,3-alternate Thiacalix[4]crown tubes.
abstract: Several new thiacalix[4]monocrown and thiacalix[4]biscrown compounds were synthesized. Their metal ion extractabilities are found to be lower than those of conventional calix[4]crowns. By use of X-ray crystal structures and (1)H NMR spectroscopy, this result is explained by weaker electrostatic interactions of the polyether ring oxygen atoms with the metal ions and diminished pi-metal ion interactions between the metal ions and the aromatic rings of the thiacalix[4]crowns. Temperature-dependent (1)H NMR spectroscopic measurements reveal coalescence temperatures T(c)(intra) and T(c)(inter) for metal ion exchange. In one case, this exchange was rationalized as metal ion shuttling through a thiacalix[4]biscrown tube. Since the metal ions are less tightly complexed by the polyether units in thiacalix[4]biscrowns than in conventional calix[4]biscrowns, more facile metal ion exchange between the two polyether units takes place in the former.
authors.affiliation: Department of Chemistry, Konyang University, Nonsan 320-711, Korea.
authors.forename: Jae Kwang
authors.initials: JK
authors.lastname: Lee
authors.forename: Sung Kuk
authors.initials: SK
authors.lastname: Kim
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bartsch
authors.forename: Jacques
authors.initials: J
authors.lastname: Vicens
authors.forename: Sotaro
authors.initials: S
authors.lastname: Miyano
authors.forename: Jong Seung
authors.initials: JS
authors.lastname: Kim