Azobenzene‐Based Macrocyclic Arenes: Synthesis, Crystal Structures, and Light‐Controlled Molecular Encapsulation and Release

Abstract

Azobenzene (azo)‐based macrocycles are highly fascinating in supramolecular chemistry because of their light‐responsiveness. In this work, a series of azo‐based macrocyclic arenes 1, 2, 3, and 4, distinguished by the substituted positions of azo groups, is rationally designed and synthesized via a fragment‐cyclization method. From the crystal and computed structures of 1, 2, and 3, we observe that the cavity size of these azo‐macrocycles decreases gradually upon E→Z photoisomerization. Moreover, light‐controlled host–guest complexations between azo‐macrocycle 1 and guest molecules (7,7,8,8‐tetracyanoquinodimethane, terephthalonitrile) are successfully achieved. This work provides a simple and effective method to prepare azo‐macrocycles, and the light‐responsive molecular‐encapsulation systems in this work may further advance the design and applications of novel photo‐responsive host–guest systems.

Dynamic Nucleophilic Aromatic Substitution of Tetrazines

“…Controlled release of guest by light is very attractive because it is a clean and switchable process which has been reported in several supramolecular systems. [ 91 , 92 , 93 , 94 , 95 ]…”

“…On one hand, we decided to prove that S N Tz allows for the easy synthesis of photo cleavable receptors. Controlled release of guest by light is very attractive because it is a clean and switchable process which has been reported in several supramolecular systems [91–95] …”

Dynamic Nucleophilic Aromatic Substitution of Tetrazines

“…Those properties together with its dynamic nature make S N Tz ap otentially valuable tool for the synthesis of functional systems.W ith all this in mind, we decided to test some of its possible applications through two examples.Onone hand, we decided to prove that S N Tz allows for the easy synthesis of photo cleavable receptors.Controlled release of guest by light is very attractive because it is ac lean and switchable process which has been reported in several supramolecular systems. [91][92][93][94][95] Owing to the abovementioned intrinsical properties of S,S-tetrazines,t hey could be employed to create receptors with the ability to release their guest after disassembly triggered by light. Actually,tetrazine-bearing crown ether 15 was synthesized in two steps in 44 %yield, and it displays an association constant of 1.1 10 2 M À1 with neurotransmitter acetylcholine hexafluorophosphate (ACh PF 6 )inacetonitrile (Figure 6b).…”

Crown Ether Functionalized Potassium‐Responsive Anionocages for Cascaded Guest Delivery

“…In biological systems,t he activity of many proteins and enzymes is regulated by binding an effector molecule, [1] which plays ac ritical role in various biological processes,s uch as signal transduction, [2] oxygen transport, [3] and enzyme catalysis. [4] Chemists have been inspired to synthesize stimuliresponsive receptors [5] forc ontrolled guest capture/release under the regulations of such effectors as ions, [6] pH, [7] light, [8] or voltage. [9] Advances in this area have promoted progress of various fields,i ncluding molecular machines, [10] supramolecular catalysis [11] and drug deliveries.…”