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The supramolecular complex formation between erichrome blue black R and P-sulfonated calixarenes:Aspectrofluorimetric study on their inclusion interaction

Cheng-Xuan Hao, Hong Tian, Hai-Long Liu, Li-Ming Du, Qing-Hua Zhao, Xiao-Hui Guo, Yun-Long Fu

The fluorescent characteristic of chrome blue black R(EBBR) and its ability of binding to p-sulfonated calix[n]arene (SCnA, n=4,6,8) as a guest moleculehave been studied by fluorescence methods and a variety of techniques. According to the fluorescence spectra, it was found that EBBR might have different conformations under different conditions of acidity, whichwas validated byUV spectrophotometer. The stability constantswere determined at different temperatures and different pH by spectrofluorometry titrations, the thermodynamic parameters of the obtained complex were evaluated and the impact of both kinds of molecules during the inclusion were measured quantitatively. The results show that the binding constants increase when the size of calixarene cavity becomes enlargedÿindicating that the larger host cavity can accommodate the guest molecule better. The impact of ionic strength on the system were further investigated. In addition, 1H NMR studies were carried out to explore the mechanisms of their interaction. It showed that EBBR partly penetrated into the cavity of p-sulfonated calix[n]arene. We found that the assumptions about steric hindrance between the sulfonic acid groups are established by molecular simulation of clathrate. The data calculated by molecular simulation is consistent with the findings obtained by fluorescence and 1H NMR.