Visual recognition of ortho-xylene based on its host-guest crystalline self-assembly with α-cyclodextrin

Weilin Qi; Xuejiao Wang; Zeyu Liu; Kaerdun Liu; Yifan Long; Wanwan Zhi; Cheng Ma; Yun Yan; Jianbin Huang

doi:10.1016/j.jcis.2021.03.024

Visual recognition of ortho-xylene based on its host-guest crystalline self-assembly with α-cyclodextrin

J Colloid Interface Sci. 2021 Sep:597:325-333. doi: 10.1016/j.jcis.2021.03.024. Epub 2021 Mar 15.

Authors

Weilin Qi¹, Xuejiao Wang², Zeyu Liu¹, Kaerdun Liu¹, Yifan Long³, Wanwan Zhi¹, Cheng Ma¹, Yun Yan⁴, Jianbin Huang⁵

Affiliations

¹ Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, PR China.
² Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, PR China; Fujian Provincial University Engineering Research Center of Industrial Biocatalysis, Fujian Normal University, Fuzhou 350007, PR China.
³ Department of Chemistry, University College London, London WC1E 6BT, UK.
⁴ Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, PR China. Electronic address: yunyan@pku.edu.cn.
⁵ Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, PR China. Electronic address: jbhuang@pku.edu.cn.

PMID: 33887560
DOI: 10.1016/j.jcis.2021.03.024

Abstract

Hypothesis: Distinguishing substituted aromatic isomers is a challenging task because of the great similarity of their physicochemical properties. Considering xylene isomers have drastically different geometrical shapes, we predict this would show great impact on the self-assembling behavior of various xylene isomer@cyclodextrin inclusion complex.

Experiments: Through host-guest crystalline self-assembly, among three isomers, only ortho-xylene is capable to form hydrogels with α-cyclodextrin. ROESY NMR, molecular simulations and circular dichroism spectra suggest that the ortho selectivity comes from the difference in the conformation of host-guest building block. The larger volume, and steric hinderance of the ortho isomer make it most possibly decrease their tendency to adopt more mobile orientations in cyclodextrin-based complex as meta and para isomers do, resulting in gel formation.

Findings: Herein, we report a novel, facile and environmentally-friendly protocol on the recognition of ortho benzene isomers using α-cyclodextrin through host-guest crystalline self-assembly. Visual recognition of ortho-xylene is achieved through amplifying the structural difference of xylene isomers at molecular scale into macroscopic scale. We believe this work unveils subtle rules to control macroscopic assemblies at the molecular level and highlights the potential of using macrocyclic compounds to improve the quality and reduce the energy bill for separation in petrochemical industry.

Keywords: Hydrogel; Macroscopic recognition; Supramolecular crystalline self-assembly; Xylene isomers; α-Cyclodextrin.