The Effects of the Solvents on the Macrocyclic Structures: From Rigid Pillararene to Flexible Crown Ether

Shuangshuang Wang,Haixin Shi,Yanzhen Yin,Xingtang Liang,Jian Gao

doi:10.21577/0103-5053.20210088

Abstract

The differences in the macrocyclic structures lead to different flexibilities, and yet the effect of solvents on the conformations is not clear so far. In this work, the conformations of four representational macrocyclic molecules (pillar[5]arene, p-tert-butyl calix[6]arene, benzylic amide macrocycle and dibenzo-18-crown-6) in three solvents with distinct polarity have been studied by all-atom molecular dynamics simulations. The structural features of the macrocycles in the solvents indicate that the conformations are related to the polarity of the solvents and the formation of hydrogen bonds. For the pillar[5]arene, the benzylic amide macrocycle and the dibenzo-18-crown-6, that cannot form intramolecular hydrogen bonds, the polarity of solvents is the major contributing factor in the conformations. The formation of intramolecular hydrogen bonds, in contrast, determinates the conformations of the calix[6]arene. Furthermore, the slight fluctuations of the structures will result in tremendous change of the intramolecular hydrogen bonds of the macrocycles and the intermolecular hydrogen bonds between the macrocycles and the solvents. The current theoretical studies that serve as a basis for the macrocyclic chemistry are valuable for the efficient structural design of the macrocyclic molecules.

Highlights

Since crown ether was discovered by C
The four molecules were constructed and energy-minimized, and immersed independently in three cubic solvent boxes using the solvate module of the visualization program VMD,26 with a headspace of at least 30 Å from each edge of the box to any atom of the macrocyclic molecules
The fluctuation range in water is greatest with 45o to 120o among the three solvents, while that in CHCl3 is minimal with 55o to 110o

Summary

Introduction

Since crown ether was discovered by C. J. Pedersen in 1967, lots of researches of macrocyclic chemistry have made rapid progress on it. From a historic point of view, macrocyclic molecules have had an enormous impact on the fields of chemistry, biology, and medicine.. From a historic point of view, macrocyclic molecules have had an enormous impact on the fields of chemistry, biology, and medicine.13-15 The architectures of these macrocyclic molecules have ordained that they are of varying degrees of flexibility and ability of forming hydrogen bonds (H-bonds). The structures of several macrocyclic molecules are shown in Scheme 1. These selected macrocyclic molecules have certain representativeness. The pillar[5]arenes (P[5]s) show unique pillar architectures and

Methods

Results

Conclusion