Chlorine Anion Encapsulation by Molecular Capsules Based on Cucurbit[5]uril and Decamethylcucurbit[5]uril

Yun-Qian Zhang,Sai-Feng Xue,Qian-Jiang Zhu,Zhu Tao

doi:10.3390/12071325

Abstract

Three barrel-shaped artificial molecular capsules 1-3, based on normal cucurbit[5]uril (Q[5]) and decamethylcucurbit[5]uril (Me10Q[5]), were synthesized and structurally characterized by single-crystal X-ray diffraction. Encapsulation of a chlorine anion in the cavity of a Q[5] or Me10Q[5] to form closed a molecular capsule with the coordinated metal ions or coordinated metal ions and water molecules in the crystal structures of these compounds is common. The three complexes [Pr2(C30H30N20O10)Cl3(H2O)13]3+ 3 Cl- x 5 H2O (1), [Sr2(C40H50N20O10)(H2O)4Cl]3+ 3 Cl- x 2 (HCl) 19 H2O (2) and [K(C40H50N20O10)(H2O)Cl] x [Zn(H2O)2Cl2] x [ZnCl4]2- x 2 (H3O)+ x 8 H2O (3) all crystallize as isolated molecular capsules.

Highlights

In past several decades, the coordination chemistry of cations has become well developed, while the chemistry of anion encapsulation is still in its infancy [1]
Calix[n]pyrroles and their derivatives, some imidazole derivatives and cryptands were used as receptors for halide anions through hydrogen bonds [8,9,10,11,12], and mercury was used as a Lewis-acidic center in a number of halide anion receptors [13]
To investigate the capability of Q[n] inclusion anions and their potential applications, we have designed and synthesized three complexes of Q[5] and Me10Q[5] in which chlorine anions are encapsulated, and we described this synthesis and their crystal structures

Summary

Introduction

The coordination chemistry of cations has become well developed, while the chemistry of anion encapsulation is still in its infancy [1]. The earliest macrocyclic receptor for anions, which coordinates to halide anions by a combination of electrostatic interactions and hydrogen bonds, was synthesized by Park and Simmons in 1968 [7]. The novel structure and the capability of forming complexes with molecules and ions make the cucurbit[n]uril family attractive, as synthetic receptors and as building blocks for supramolecular assemblies such as rotaxanes, catenanes, and molecular machines[24,25,26,27,28,29,30]. To investigate the capability of Q[n] inclusion anions and their potential applications, we have designed and synthesized three complexes of Q[5] and Me10Q[5] in which chlorine anions are encapsulated, and we described this synthesis and their crystal structures

Results and Discussion

Synthesis

Crystal Structure Determination

C40H78N20O23KZn2Cl7