p-sulfonatocalix[7]arene: synthesis, protolysis, and binding ability

摘要

Water-soluble p-sulfonatocalix[7]arene 1 has been synthesized in good yield through standard procedures and its conformational preferences have been investigated by Monte Carlo conformational searches. The acid-base properties of 1 were investigated by means of potentiometric titration, obtaining pK(a) values in agreement with those reported for other p-sulfonatocalix[n]arene homologs. The binding ability of I toward organic quaternary ammonium cations such as Diquat (2), Paraquat (3), and Chlormequat (4) was investigated by means of H-1 NMR titrations in D2O at pD=7.3, DOSY NMR measurements, and 2D RCESY NMR spectroscopy. Spectrofluorimetry proved to be a useful method for the determination of trace amounts of 2 and 3 in aqueous solution by using Acridine Orange bound to 1 as a chemical indicator. (C) 2008 Elsevier Ltd. All rights reserved.