Cyclodextrins as molecular scaffolds for anion and cation recognition.

摘要

The synthesis of inner-sphere and outer-sphere ligands using cyclodextrin as a molecular scaffold are detailed. The outer-sphere effect of counter-ions on crystal packing of metal-ligand complexes and the crystallographic structure of a cyclodextrin inclusion complex are also addressed.; Amine-functionalized cyclodextrins have been synthesized for use in the outersphere binding of uranyl carbonate, [UO2(CO3) 3]4-. The binding constants of the outersphere ligands with uranyl carbonate were determined by 1H NMR titrations. NMR and IR spectroscopy were used to evaluate the molecular interactions of each with uranyl carbonate.; The outer-sphere effects of various counter-ions, A, on the hydration and packing of M2+ nitrilotriacetate (NTA) complexes of the form A[M2+(NTA)]•(H2O)x is compared, where A = Li+, Na+, K+ and M 2+ = Co, Cu, Zn. The counter-ion plays the dominant role in the crystal packing; the metal radius plays only a limited structural role. Variations in unit cell size are directly related to the size of the complex counter-ions and the concomitant outer-sphere interactions with the [M(NTA)]- anion.; Carboxylic acid-functionalized beta-cyclodextrin derivatives have been synthesized for use in the inner-sphere binding of the lanthanides. The binding constants of these ligands with the lanthanides were determined by potentiometric titrations. The denticity of the ligands was determined by time resolved laser fluorescence spectroscopy. These ligands have a high affinity for the lanthanides with log K values ranging from 18 to 116.; A 2:1 complex between beta-cyclodextrin and N-methyl anthranilic acid has been studied in the solid state. The cyclodextrin forms a head-to-head channel-type structure with the N-methyl anthranilic acid lying between the beta-cyclodextrin in a sandwich fashion, which is held in place by an extensive hydrogen-bonding network between the cyclodextrins and the N-methyl anthranilic acid.