Supramolecular properties of amphiphilic adamantylated azo dyes

Abstract

Despite environmental and health risks, azo dyes are still very popular colourising agents; therefore, methods for removing the dyes and/or related pollutants from wastewater have been developed. We have incorporated a lipophilic adamantane cage into two polar disulphonatonaphthalene-1-azobenzene dyes to prove the concept that modified dyes can be treated via host–guest supramolecular interactions using suitable cyclodextrin (CD) and cucurbit[n]uril (CBn) hosts. We conducted 1H NMR experiments to demonstrate that both dyes form specific inclusion complexes with an adamantane cage buried inside the CB7 or β-CD cavity. Using isothermal titration calorimetry, we determined association constants with β-CD and CB7 in the range of (0.7–1.3) × 106 and (1.4–3.4) × 108, respectively. As the dye@CB7 complexes were sparingly soluble in water, the dye can be efficiently removed from water by precipitation, even in the presence of β-CD. © 2021 Elsevier Ltd