Metal-Organic Coordination Polymers Formed from γ-Cyclodextrin and Divalent Metal Ions

The chemistry of metal-organic frameworks based on cyclodextrins and alkali metals has been extensively investigated in recent years, but coordination polymers with non-alkali metals have been rarely reported. Here, we describe the synthesis and X-ray crystallographic characterization of a series of coordination polymers, [Ba(H2O)(3)(gamma-CD)]Cl-2 center dot 6H(2)O (gamma-CD-Ba1), [Ba(H2O)(gamma-CD)]Cl-2 center dot 8H(2)O (gamma-CD-Ba2), [Sr(H2O)(gamma-CD)](NO3)(2)center dot 9H(2)O (gamma-CD-Sr), [Ca(gamma-CD)(2)]Cl-2 center dot 2CH(3)OH center dot 16H(2)O (gamma-CD-Ca), and [Pb(H2O)(gamma-CD)](NO3)(2)center dot 11H(2)O (gamma-CD-Pb), which were obtained by reacting gamma-cyclodextrin with alkaline earth metal ions and Pb2+. The coordination polymers formed from gamma-cyclodextrin and Ca2+ and Ba2+ are obtained for the first time. The only compound in the studied series, gamma-CD-Ba1, has a 3D structure. The other compounds have layered structures. In the structure of gamma-CD-Ca, the coordination and number of gamma-cyclodextrin molecules connected to the Ca2+ are different from those determined for a series of isostructural 2D coordination polymers, namely, gamma-CD-Ba2, gamma-CD-Sr and gamma-CD-Pb. The metal-organic coordination polymer gamma-CD-Pb exhibits photoluminescence in the near UV-region (lambda(max) = 345 nm).