Sulfonate ligand-induced formation of alkali metal–cucurbit[5]uril-based assemblies

Abstract

Herein, we report the use of 1,5-naphthalene disulfonic acid (H₂NDS) as a structure-directing agent to construct cucurbit[5]uril-based supramolecular assemblies. In order to demonstrate the directing role played by H₂NDS. {Q[5]·3[H₃O]·3Cl·11H₂O} (1) and {Q[5]·H₂NDS·13H₂O} (2) were separately synthesized by recrystallization of Q[5] from HCl solution in both the absence and the presence of H₂NDS. Following the addition of alkali metal cations to the Q[5]–H₂NDS system, four novel assemblies with the formulae {[Na₂(H₂O)₂(Q[5])(NDS)_0.5]·(NDS)_0.5·7H₂O} (3), {[K₂(H₂O)₃(Q[5])]·(NDS)·4H₂O} (4), {[Rb₂(H₂O)₄(Q[5])]·(NDS)·4H₂O} (5) and {[CsK(H₂O)₅(Q[5])]·(NDS)·4H₂O} (6) were obtained. Single-crystal X-ray diffraction studies revealed that all of these metal-containing assemblies have similar general structures to that of 2, with the main differences being the coordination modes of the metal cations in 3–6. Furthermore, relevant experiments revealed that compound 2 can highly selectively detect NFX (norfloxacin) molecules as a ratio type fluorescent probe and also is able to capture acridine red (AR), crystal violet (CV) and methylene blue (MB) from aqueous media and the resulting dye-loaded samples can function as solid fluorescent materials.