Supramolecular coordination assemblies of a symmetrical octamethyl-substituted cucurbituril with alkali metal ions based on the outer-surface interactions of cucurbit[n]urils

Abstract

Interactions of alkali cations (A+ = Na+, K+, Rb+, Cs+) with a symmetrical octamethyl-substituted cucurbituril (OMeQ[6]) have been investigated in the presence of different structure-directing agents. Single-crystal X-ray diffraction analysis has revealed that the interaction results in the formation of coordination complexes of OMeQ[6] with K+ and Cs+ cations in OMeQ[6]–ACl–HCl systems, whereas no complexes were obtained from systems containing Na+ and Rb+ in the presence of polychloride cadmium anions such as [Cd2Cl8]4−, [CdCl4]2−, or [Cd2Cl7]3− as structure-directing agents; in the presence of p-hydroxybenzoic acid (Hyb) as a structure-directing agent, the interaction results in the formation of coordination complexes of OMeQ[6] with Na+ and Cs+ cations in OMeQ[6]–ACl–H2O systems. More importantly, in the presence of these different structure-directing agents, OMeQ[6] or OMeQ[6]/A+ complexes can form different supramolecular assemblies based on the outer surface interaction of Q[n].