Studies on the Inclusion Behavior of Amphiphilic p-Sulfonatocalix[4]arene with Ascorbic Acid by Spectrofluorometric Titrations

Abstract

The aqueous solution of tetrabutyl ether derivatives of p-sulfonatocalix[4]arene (SC4Bu) and ascorbic acid (AA) complex has been studied based on fluorescence and <sup>1</sup>H NMR spectroscopic results. It was found that the fluorescence intensity of SC4Bu quenched regularly upon the addition of AA. A 1:1 stoichiometry for the complexation was established and was verified by Job’s plot. The temperature-dependent inclusion constants were calculated, form which Δ H and ΔS values were calculated. Meanwhile the proposed interaction mechanism of the inclusion complex was discussed based on <sup>1</sup>H NMR results. The various factors (ionic strength, and surfactants) effecting the inclusion process were examined in detail

Investigation into Drug Solubilisation Potential of Sulfonated Calix[4]Resorcinarenes

“…In particular, there is an established evidence base confirming that water-soluble calix[n]arenes which possess sulfonate groups in the 4-position on the upper rim are capable of solubilising drug molecules which otherwise possess poor solubility in aqueous media [9][10][11][12][13][14][15][16][17][18][19][20][21]. However, few investigations into the properties and utility of simple calix[4]resorcinarenes which bear sulfonate groups in the 2-position on the upper rim have been reported.…”

Simple Calix[n]arenes and Calix[4]resorcinarenes as Drug Solubilizing Agents

“…A derivative of para-sulfonatocalix [4]arene bearing tetrabutyloxy groups in place of the hydroxyl groups on the lower rim was shown to form a stoichiometric complex with ascorbic acid in water [54]. Interestingly the association constant, determined by fluorescence spectroscopy, increased dramatically as the temperature of the solution increased, indicating that entropy plays a significant role in determining the degree of complexation.…”

“…Interestingly the association constant, determined by fluorescence spectroscopy, increased dramatically as the temperature of the solution increased, indicating that entropy plays a significant role in determining the degree of complexation. NMR studies demonstrated that the ascorbic acid molecule was complexed such that the hydroxylated chain was embedded within the hydrophobic cavity, leaving the unsaturated lactone moiety projected out of the cavity facilitating the formation of a hydrogen-bonded network with the sulfonate functional groups [54].…”