Molecular binding behavior of a bispyridinium-containing bis(β-cyclodextrin) and its corresponding [2]rotaxane
Ying-Ming Zhang1, Ze Wang, Yong Chen
1Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300071, P. R. China. yuliu@nankai.edu.cn.
Abstract:
Bispyridinium-bridged bis(β-cyclodextrin) () and its corresponding [2]rotaxane () were synthesized by a 'click' reaction, in which two different types of macrocycles, cucurbit[7]uril and β-cyclodextrin, are employed as the wheel component and bulky stopper, respectively. Moreover, the molecular binding behaviors of hosts and with four bile salts, namely, the sodium salts of cholic acid (CA), deoxycholic acid (DCA), glycocholic acid (GCA), and taurocholic acid (TCA), were comparatively investigated by (1)H NMR spectroscopy and isothermal titration calorimetry experiments. The spectroscopic and microcalorimetric results can jointly demonstrate a cucurbituril-mediated binding process; that is, the introduction of cucurbit[7]uril has a pronounced impact on the electrostatic attraction and hydrogen-bonding interaction between the bispyridinium spacer in the host molecules and the hydrophilic terminal group in the guest molecules, ultimately giving a significant change in the thermodynamic origins of these supramolecular complexes.
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