Cucurbit[6]uril-based multifunctional supramolecular assemblies: synthesis, removal of Ba(ii) and fluorescence sensing of Fe(iii)

Abstract

A novel cucurbit[6]uril-based (Q[6]) supramolecular assembly {(NH₄)₂·Q[6]·(HDTNB)₂·2H₂O} (1) with a three-dimensional (3D) framework structure was successfully constructed via outer-surface interactions between Q[6] and a flexible aromatic compound, 5,5′-dithiobis-(2-nitrobenzoic acid) (H₂DTNB), as a structure-directing agent. It is interesting to find that assembly 1 can selectively capture Ba(II) cations among the common alkaline-earth metal ions of Mg(II), Ca(II), Sr(II) and Ba(II), resulting in the formation of an isomorphic 3D assembly {Ba(H₂O)₂Q[6]}·(HDTNB)₂ (2). Furthermore, both assemblies 1 and 2 exhibit the selective sensing of Fe(III) ions through fluorescence quenching, which has rarely been reported for Q[n]-based supramolecular assemblies.