Functional Materials with Pillarene Struts

Abstract

Conspectus Pillar­[n]­arenes (pillarenes for short) are a relatively new generation of macrocyclic host compounds with rigid cylinder architectures containing several hydroquinone units that are bridged by methylene (−CH2−) at their para positions. The investigation of pillarenes has expanded from the sole domain of supramolecular chemistry to invoke immense interest among scientists striving to exploit intelligent materials or functional systems, with regard to their fascinating attributes such as symmetric structures, tailorable functionalization, and unique host–guest properties. Over the past few years, researchers have focused on the construction of prominent supramolecular architectures such as supramolecular switches, supramolecular polymers, and self-assembled amphiphilic systems on the basis of host–guest chemistry in collaboration with other noncovalent interactions. One of the most attractive characteristics of these supramolecular assemblies relies on the tunable mechanical motions via switching of the most conformationally and thermally stable structures in a dynamic and reversible manner, which could be affected by the external conditions and enable the reciprocal effect with surrounding environments. Consequently, macrocyclic arenes are the key components of stimuli-responsive supramolecular assemblies, serving as important candidates in the construction of advanced supramolecular materials, including organic functional systems and organic–inorganic hybrid systems. In this Account, we present a relatively elaborate summary of the significant and typical intelligent systems containing pillarenes and their extended versions with a focus on our own contributions to this field during the past decade. Finally, in the last section of the review, challenges and perspectives are given.

Aggregation Mode, Host‐Guest Chemistry in Water, and Extraction Capability of an Uncharged, Water‐Soluble, Liquid Pillar[5]arene Derivative

“…Pillararenes, first synthesized by Ogoshi in 2008, [33] have cylindrical structures and have become widely used building blocks for supramolecular chemistry in the last decade [34–36] . Pillararenes have been used for sensing and separation, as platforms for new materials, as drug delivery systems, and more [37–48] . This occurred, partially, since both organic‐ and more importantly water‐soluble pillararenes, having good host‐guest capabilities, can be constructed relatively easily [34–48] .…”

“…[ 34 , 35 , 36 ] Pillararenes have been used for sensing and separation, as platforms for new materials, as drug delivery systems, and more. [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] This occurred, partially, since both organic‐ and more importantly water‐soluble pillararenes, having good host‐guest capabilities, can be constructed relatively easily. [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] Most of the water‐soluble pillararenes prepared to date have been constructed by substituting the pillararene core with charged moieties.…”

“…[ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] This occurred, partially, since both organic‐ and more importantly water‐soluble pillararenes, having good host‐guest capabilities, can be constructed relatively easily. [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] Most of the water‐soluble pillararenes prepared to date have been constructed by substituting the pillararene core with charged moieties. Indeed, uncharged water‐soluble pillararene species are scarce, and those that are liquid at room temperature are even more rare.…”

A Fluorescent Linear Conjugated Polymer Constructed from Pillararene and Anthracene

“…Supramolecular assemblies have been widely reported to assist in constructing CP-based artificial light-harvesting systems [ 18 ]. With the rapid development of supramolecular chemistry, various macrocyclic compounds with rigid structures have been designed and synthesized [ 19 , 20 , 21 , 22 , 23 ]. Benefiting from their facile synthesis, high yield, rigid cavity structures, and easy modification, pillararenes and their derivatives, as a relatively new class of synthetic macrocycles, have been widely applied for the design of high-performance fluorescent supramolecular polymeric materials [ 24 , 25 , 26 , 27 , 28 ], guaranteeing a variety of applications in fluorescence imaging [ 29 , 30 ], substance detection [ 31 , 32 ], electroluminescence materials [ 33 , 34 , 35 , 36 , 37 , 38 ], and fluorescence sensor [ 39 , 40 , 41 , 42 ].…”

Supramolecular Amphiphiles Based on Pillar[5]arene and Meroterpenoids: Synthesis, Self-Association and Interaction with Floxuridine

“…[ 13 ] have a tendency to form “host-guest” complexes [ 14 ]. At the same time they have a number of attractive characteristics, such as synthetic accessibility, planar chirality, a tubular spatial structure that forms an electron-donor cavity, and, as a consequence, the ability to accommodate fragments of “guests” in the macrocyclic ring [ 15 ]. Pillar[n]arenes tend to form complexes with positively charged molecules or molecules containing electron withdrawing groups [ 16 ].…”