Coordination and supramolecular assemblies of meta-hexamethyl-substituted cucurbit[6]uril with alkali metal ions

Coordination assemblies have been investigated by reactions between alkali metal salts and a meta-hexanomethyl-substituted cucurbit[6]uril (m-HMeQ[6]) in aqueous solutions. X-ray diffraction analysis revealed that each m-HMeQ[6] coordinates with three alkali metal ions, K+, Rb+ or Cs+ and forms a 1:2, m-HMeQ[6]:Malkali+ complex. This complex forms a one-dimensional supramolecular chain through hydrogen bonding. The m-HMeQ[6]/Malkali+ complex-based chains often form honeycomb-like frameworks in which each channel is filled with counter anions and water molecules. The driving forces resulting in the formation of such supramolecular assemblies could be attributed to the outer-surface interaction of Q[n]s.

X-ray crystal structure: (a) overall view of m-HMeQ[6]/Rb+ complex-based honeycomb-like supramolecular assembly, (b) channel in the assembly is filled with Cl− anions and water molecules, and details of interactions of (c) m-HMeQ[6] molecule with Cl− anions, and (d) six neighboring m-HMeQ[6] molecules in a honeycomb cell.Figure optionsDownload as PowerPoint slide