Flexible imidazolium macrocycles: building blocks for anion-induced self-assembly

Abstract

This feature article summarises recent contributions of the authors in the area of anion-induced supramolecular self-assembly. It is based on the chemistry of a set of tetracationic imidazolium macrocycles, specifically the so-called 'Texas-sized' molecular box, cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,4-dimethylenebenzene) (1), and its congeners, cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,2-dimethylenebenzene) (2), cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,3-dimethylenebenzene) (3), and cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](2,6-dimethylenepyridine) (4). These systems collectively have been demonstrated as being versatile building blocks that interact with organic carboxylate or sulfonate anions, as well as substrates (e.g., neutral molecules or metal cations). Most work to date has been carried out with 1, a system that has been found to support the construction of a number of stimuli responsive self-assembled ensembles. This macrocycle and others of the 'Texas-sized' box family also show the potential to react as carbene precursors and to undergo post-synthetic modification (PSM) to produce new functional macrocycles, such as trans- and cis-cyclo[2]((Z)-N-(2-((6-(1H-imidazol-1-yl)pyridin-2-yl)amino)vinyl)formamide)[2](1,4-bismethylbenzene) (5 and 6, respectively). On the basis of the work reviewed in this Feature article, we propose that the imidazolium macrocycles 1-4 can be considered as useful tools for the construction of ensembles with environmentally responsive features, including control over self-assembly and an ability to undergo precursor-specific PSM.

Phosphate–phosphate oligomerization drives higher order co-assemblies with stacks of cyanostar macrocycles

“… 8 As such, these species represent a new motif capable of supporting self-assembly. 9 , 10 While commonplace in the solid state, 6 – 8 , 11 – 23 and anticipated in theory as triply or doubly hydrogen-bonded dimers, 24 , 25 phosphate oligomerization is rare in solution. Like charges in anion–anion species display long-range repulsions, not attractions.…”

“Texas-Sized” Molecular Boxes: From Chemistry to Applications

“…It was found that most aromatic anions with “widths” less than 5.8 Å thread through the cavity of macrocycle 1 to form pseudorotaxanes. For ease of reference, this was termed the “insert” binding mode ( Figure 1 ) [ 38 , 47 , 48 , 50 ]. Meanwhile, in the case of larger conjugated aromatic anions, it was found that TxSB 1 can serve as “molecular tweezers”, giving rise to sandwich-like complexes.…”

“…This image is a modification of one that first appeared in ref. [ 50 ] and is reproduced with permission. Copyright 2015 The Royal Society of Chemistry.…”

Complete and Versatile Post‐Synthetic Modification on Iron‐Triazole Spin Crossover Complexes: A Relevant Material Elaboration Method

“…In recent years the post-synthetic modification (PSM) method has attracted more attention as an efficient tool to perform a chemical transformation on previously synthesized materials such as metal-organic frameworks (MOFs), [1][2][3][4] covalent organic frameworks (COFs), [5] quantum dots, [6] carbon dot, [7] biomolecules, [8][9][10][11] polymers, [12] supramolecular assemblies. [13,14] The term "post-synthetic modification" was first introduced by Cohen and Wang [15] in the PSM of MOFs as an analogy to protein post-translational modification (PTM). [16] Post-synthetic method can be defined as a chemical modification on a fabricated material rather than using the molecule precursors.…”