Complexation study and spectrofluorometric determination of the binding constant for diquat and p-sulfonatocalix[4]arene

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• 作者：Siné ; ad M. Mc Dermott ; ^{sinead.mcdermott@nuim.ie} ; Denise A. Rooney ; Carmel B. Breslin
• 关键词：Diquat ; p-Sulfonatocalix[4]arene ; Ionic strength ; Complexation constant
• 刊名：Tetrahedron
• 出版年：2012
• 期刊代码：107_00404020
• 类别：ch
• 出版时间：20 May, 2012
• 卷：68
• 期：20
• 页码：3815-3821
• 文件大小：559 K

摘要

The interactions between diquat (DQ) and p-sulfonatocalix[4]arene (C4S) were studied in an aqueous solution as a function of the ionic strength. Evidence for the formation of a complex between DQ and C4S was obtained using fluorescence measurements, while the stoichiometry of the complex was confirmed as 1:1 for DQ/C4S using UV-vis spectroscopy. The ionic strength had no influence on the stoichiometry of the complex, but exerted a significant influence on the complexation constant, K_c, decreasing with an increase in the ionic strength. The thermodynamic complexation constant, K_c鈥? was computed as 5.25卤1.11脳10⁷ using the extended Debye-H眉ckel law. The rate constants for the heterogeneous electron transfer for the reduction of DQ at an electrode surface were evaluated as 0.150卤0.010 cm s^鈭? in the absence of C4S and 0.065卤0.010 cm s^鈭? when C4S was added to the solution in a 1:1 ratio.