Enhanced Zn2+ ion-sensing behavior of a benzothiazole derivative on encapsulation by β-cyclodextrin

Abstract

We report, in this paper, a benzothiazole derivative which shows selective binding of zinc ions among a pool of metal ions and the enhanced selectivity of the same metal ion by the derivative in its β-cyclodextrin bound form. The Zn²⁺ ion binding is studied using UV-visible absorption and fluorescence spectroscopy. The stoichiometry and binding mode of the benzothiazole derivative-β-cyclodextrin complex are determined using 1D and 2D NMR spectroscopic analysis. The cyclodextrin molecule slides over the benzothiazole derivative and resides above the aminomethyl group linking the benzothiazole and dihydroxyphenyl moieties. The site of binding of the Zn²⁺ ion with the compound remains the same both in the compound's free and cyclodextrin-complexed forms. Molecular modeling studies were also carried out in order to obtain more details about the cyclodextrin-compound and Zn²⁺-compound interactions, and their results are in close agreement with obtained experimental data.