Coordination of fully substituted cyclopentano cucurbit[5]uril with alkali cation in the presence of tetrachloridezicate anion

• Study the coordination of CyP5Q[5] and alkali metal ions in the presence of [ZnCl4]2− anions by means of X-ray crystallography.
• The [ZnCl4]2− anion is involved in the coordination with Rb+ and Cs+ cations, resulting in the formation of supramolecular chains.
• Investigation to the analysis of the absorption capacities for CyP5Q[5] based supramolecular assemblies.

Coordination of fully substituted cyclopentano cucurbit[5]uril (CyP5Q[5]) with an alkali cation (A+) in the presence of tetrachloridezicate anions was investigated. Single-crystal X-ray diffraction analysis revealed that the CyP5Q[5]–Na+ and K+–[ZnCl4]2−–HCl interaction systems yielded an A+/Cl−@CyP5Q[5]/A+-type molecular capsule, and that a chloride anion was included in the cavity of the CyP5Q[5] molecule. [ZnCl4]2− anions were not involved in direct coordination with the A+/Cl−@CyP5Q[5]/A+ capsule. The CyP5Q[5]–Rb+ and Cs+–[ZnCl4]2−–HCl interaction systems yielded an A+/CyP5Q[5]/A+-type molecular capsule shell, and no chloride anions were included in the cavity of the CyP5Q[5] molecule. [ZnCl4]2− anions directly interacted with coordinated Rb+ or Cs+ cations through electrostatic interaction, and [ZnCl4]2− anions in particular played the role of linkers, resulting in the formation of a linear supramolecular assembly ⋯[ZnCl4]2−–A+/Cl−@CyP5Q[5]/A+–[ZnCl4]2−–A+/Cl−@CyP5Q[5]/A+⋯. Close inspection revealed that the obtained CyP5Q[5]/A+-based supramolecular assemblies (A = Na, K, Rb, Cs) presented different porous conformation and could show different absorption properties.

It is worth noting that the adjacent Na+/Cl@CyP5Q[5]/Na+ capsule are further linked by H-bond in compound 1, leading to the formation of a 1D linear chain structure. Interestingly, the [ZnCl4]2− anions were helix arranged around the 1D linear chain with Zn1–Zn1 distances ranging from 12.104(7) to 13.916(6) Å (Fig. 5), while the [ZnCl4]2− anions play the important role of bridging in compound 4 (Fig. 4a). This phenomenon can be explained by the interaction between [ZnCl4]2− anions and CyP5Q[5] molecules Vs the metal ions.Figure optionsDownload as PowerPoint slide