1. 贵州大学大环化学及超分子化学重点实验室，贵州 贵阳 550025 2. 贵州大学西南药用生物资源教育部工程研究中心，贵州 贵阳 550025 3. 贵州省天然产物重点实验室，贵州 贵阳 550009 4. Commonwealth Scientific and Industrial Research Organization (CSIRO), Manufacturing Flagship, P.O. Box 218, Lindfield, NSW, 2070 Australia
Interaction of Cucurbit[8]uril with β-Indoleacetic Acid and Methylviologen
SONG Gui-xian1, TANG Qing2, HUANG Ying2*, ZHANG Jian-xin3, TAO Zhu1, XUE Sai-feng1, ZHU Qian-jiang1, WEI Gang4*
1. Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou University, Guiyang 550025, China 2. The Engineering and Research Center for Southwest Bio-Pharmaceutical Resourcesl Ministry of Education of Guizhou University, Guiyang 550025, China 3. Key Laboratory of Chemistry for Natural Products of Guizhou Province, Guiyang 550009, China 4. Commonwealth Scientific and Industrial Research Organization (CSIRO), Manufacturing Flagship, P.O. Box 218, Lindfield, NSW 2070, Australia
Abstract：The interaction between Q[8] with β-indoleacetic acid and the methylviologen was studied in aqueous solution with electronic absorption spectroscopy (UV-Vis), fluorescence spectroscopy, 1H NMR spectroscopy and isothermal titration calorimetry (ITC) in details. The authors explored the mode of action, action site and thermodynamic properties of the host-guest system. The electronic absorption and fluorescence spectroscopy data showed that the Q[8]/IAA system and Q[8]/MV2+ system informed 1∶1 inclusion complexes in aqueous solution. ITC results showed that the changes of Gibbs free energy and enthalpy are all negative, it suggested that complex formation was spontaneous and exothermic reaction. Moreover, ITC results for the Q[8] and IAA with MV2+ indicate that the association constants of the Q[8]-IAA and Q[8]-MV2+ complexes were (3.22±0.96)×105 L·mol-1 and (3.90±0.91)×106 L·mol-1, respectively. Therefore, the interaction between Q[8] and IAA with the MV2+ was a competitive process. This likely occurs because the MV2+ and IAA molecules attempt to occupy the Q[8] cavity, which reduces the fluorescence and absorption spectra intensity of Q[8]-IAA because of the formation of a new inclusion complex between Q[8] and IAA with MV2+. In addition, with the addition of MV2+ to a Q[8]/IAA complex, 1H NMR results showed that the indole moieties of β-indoleacetic acid and bipyridyl group of methylviologen can be incorporated into Q[8] cavities because of electronic transfer MV2+ with PQ in a Q[8] cavity with ternary complexes. These results provides the potential applications for the supramolecular self-assembly in cucurbit[n]urils field.
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