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

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]middot3[H3O]middot3Clmiddot11H(2)O} (1) and {Q[5]middotH(2)NDSmiddot13H(2)O} (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 {[Na-2(H2O)2(Q[5])(NDS)(0.5)]middot(NDS)(0.5)middot7H(2)O} (3), {[K-2(H2O)3(Q[5])]middot(NDS)middot4H(2)O} (4), {[Rb-2(H-2-O)(4)(Q[5])]middot(NDS)middot4H(2)O} (5) and {[CsK(H2O)5(Q[5])]middot(NDS)middot4H(2)O} (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.