Rapid metal ions shuttling through 1,3-alternate Thiacalix[4]crown tubes |
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Authors: | Lee Jae Kwang Kim Sung Kuk Bartsch Richard A Vicens Jacques Miyano Sotaro Kim Jong Seung |
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Institution: | Department of Chemistry, Konyang University, Nonsan 320-711, Korea. |
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Abstract: | Several new thiacalix4]monocrown and thiacalix4]biscrown compounds were synthesized. Their metal ion extractabilities are found to be lower than those of conventional calix4]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 thiacalix4]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 thiacalix4]biscrown tube. Since the metal ions are less tightly complexed by the polyether units in thiacalix4]biscrowns than in conventional calix4]biscrowns, more facile metal ion exchange between the two polyether units takes place in the former. |
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