Abstract
It has been a challenging topic and perpetual task to design and synthesize covalent macrocycles with characteristic self-assembling behaviors and excellent host-guest properties in supramolecular chemistry. Herein, we present a family of macrocyclic diphenylamine[n]arenes (DPA[n]s, n = 3–7) consisting of methyldiphenylamine units through a facile one-pot synthesis strategy. Unlike many other reported macrocyclic arenes, the resultant non-planar DPA[n]s feature intrinsic π-π stacking interactions, interesting self-assembling behaviors and ethene/ethyne capture properties. Specifically, strong multiple intermolecular edge-to-face aromatic interactions in DPA[3] have been systematically investigated both in solid and solution states. The intriguing findings on the intermolecular edge-to-face stacking interaction mode in the macrocycle would further highlight the importance of noncovalent π-π interaction in supramolecular self-assembly. This study will also shed light on the macrocyclic and supramolecular chemistry and, we expect, will provide a direction for design and synthesis of covalent macrocycles in this area.
Highlights
It has been a challenging topic and perpetual task to design and synthesize covalent macrocycles with characteristic self-assembling behaviors and excellent host-guest properties in supramolecular chemistry
The idea of deliberately choosing methyldiphenylamine as building block is based on the following considerations: (a) the electron rich nature of N-substituted diphenylamine ensures that the dynamic Friedel-Crafts (FC) alkylation reaction can only occur at the para position, which is useful for the macrocycle formation; (b) the macrocycles with methylene and nitrogen bridges will display the well-tuned cavity and intrinsic conformation, which may produce interesting solidstate packing motif and self-assembling behavior; (c) lone pairs on nitrogen can participate in resonance and increase the electron density of DPA[n]s and enhance the binding affinity towards the guest molecules
The substrate N-methyldiphenylamine containing nitrogen atom facilitates the FC alkylation reaction that proceeds at the paraposition, which is useful for the macrocycle formation
Summary
It has been a challenging topic and perpetual task to design and synthesize covalent macrocycles with characteristic self-assembling behaviors and excellent host-guest properties in supramolecular chemistry. Unlike many other reported macrocyclic arenes, the resultant non-planar DPA[n]s feature intrinsic π-π stacking interactions, interesting self-assembling behaviors and ethene/ethyne capture properties. Design and synthesis of macrocycles featuring characteristic host-guest properties and self-assembling behaviors are always one of the cutting-edge research topics in the supramolecular chemistry. It is of high interest to efficiently prepare macrocycles possessing characteristic self-assembling behaviors, excellent host-guest properties, as well as some intriguing intermolecular non-covalent interactions. To the best of our knowledge, there are few macrocyclic arenes capable of self-assembling into columns via the purely intermolecular edge-to-face aromatic interactions. DPA[3] capable of hosting both ethene and ethyne gases, which is directly confirmed by X-ray crystallography in this work, represents a very rare host material in the area of gas storage and separation
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