Efficient Aggregation‐Induced Emission Manipulated by Polymer Host Materials

Abstract

luminogens with aggregation-induced emission (AIE) properties, referred to as AIEgens, first discovered by Tang and coworkers in 2001, exhibit enhanced emission in the aggregated state, [1] leading to the rapid development of AIE materials with diverse applications in ion detection, [2] explosive sensors, [3] cell imaging, [4] photodynamic therapy, [5] optoelectronic systems, [6] and light-harvesting systems. [7] A seminal approach to fabricate smart luminescent materials is the manipulation of AIEgens with supramolecular macrocycle-based host-guest chemistry, which could induce remarkable enhancement of fluorescence intensity of materials due to the host-guest interactions between macrocycles and AIEgens that restrict the intramolecular rotation of luminophores.[8] Pillar[n]arenes, as a new generation of synthetic macrocyclic hosts first reported by Ogoshi et al. in 2008, have proved captivating advantages including symmetrical and rigid structure, versatile functionality, [9] and good solubility. [10] Among the members of the pillar[n]arene family, pillar[5]arene and its derivatives, in which 1,4-disubstituted hydroquinones are connected by five methylene units in the 2,5-positions, exhibit the advantages of: 1) desirable host candidate to bind neutral molecules in organic solvents due to the electron-rich cavity; [11] 2) high yielding in the preparation process for further functionalization; [12] and 3) rigid structure donated stiff component in the fabrication of functional materials, and have showed great potential in sensors, [13] biomedical field, [14] catalysts, [15] separation and storage, [16] supramolecular gels, [17] and light-harvesting systems. [18] For instance, Huang and co-workers constructed an elegant host-guest inclusion complex from water-soluble pillar[6]arene and a tetraphenylethene (TPE) derivative that exhibited strong fluorescence in dilute solution. [19] Interestingly, fluorescent supramolecular assemblies that possess stimuli-responsive properties and dynamic features have been fabricated from AIEgen-containing building blocks, in particular with the aid of supramolecular macrocycles, such as crown ethers, [20] calix[n]arenes, [21] cyclodextrins, [22] cucurbit[n] urils, [23] and pillar[n]arenes, [21,24] instead of simple addition of poor solvents to induce the formation of disorganized aggregates. However, research on the cooperative manipulation of AIE by a polymer host material that contains many synthetic macrocycles installed on one single polymer chain has rarely Linear copolymer hosts bearing a number of pillar[5]arene dangling side chains are synthesized for the facile construction of highly emissive supramolecular polymer networks (SPNs) upon noncovalently cross-linking with a series of tetraphenyethylene (TPE)-based tetratopic guests terminated with different functional groups through supramolecular host-guest interactions. An extremely high fluorescence quantum yield (98.22%) of the SPNs materials is obtained in tetrahydrofuran (THF) by fine-tuning the parameters...

Nanomaterials with Supramolecular Assembly Based on AIE Luminogens for Theranostic Applications

“…For example, Yang and co-workers constructed a supramolecular polymer network with high emission and efficient AIE manipulation. [119] Ma et al constructed a fluorescence on/off switch with the photo-controllable feature, based on a pseudo[3]rotaxane consisting of an AIE-active pillar[5]arene and photo-responsive guest. [118] Pillar[n]arenes, especially their water-soluble derivatives, have been proved to possess low cytotoxicity and good biocompatibility, thereby indicating their ability to serve as appealing candidates for the construction of biosensors and biomedicines.…”

Aggregation‐induced emission systems involving supramolecular assembly

“…[24] Copyright 2018, Wiley-VCH VerlagGmbH&Co. KGaA, Weinheim and proved to possess even higher enhancement degree in the respect of fluorescence intensity and quantum yields. [25,26] Definitely other supramolecular macrocycles have also been used in the supramolecular assemblies for AIEgens and are able to present their unique features in the assembling processes. For instance, crown ethers can lead to assemblies by specifically chelating with K + at a 2:1 host guest binding stoichiometry and in a sandwich mode, thus weaving AIEgens into the structures, [27] while CAs can assemble several guest-bearing AIEgens concurrently and achieve emission enhancement, which is known as calixarene-induced aggregation.…”

Pillar[5]arene-based tunable luminescent materials via supramolecular assembly-induced Förster resonance energy transfer enhancement

“…[24][25][26][27][28][29] A variety of pillararene-based supramolecular assemblies have been reported, which have been extensively used across a plethora of fields including molecular switches and molecular machines, 30,31 metal-organic frameworks, 32 controlled drugdelivery systems, [33][34][35][36][37][38] artificial transmembrane channels, [39][40][41] sensors, [42][43][44][45][46][47][48] stimuli-responsive materials, [49][50][51][52][53][54][55] hybrid absorbents, [56][57][58][59] and biomedical applications, [60][61][62][63][64][65] including as virus inhibitors and antimicrobials. 64,65 Several pillararene-based fluorescent systems combined with tetraphenylethene (TPE) [66][67][68] and/or 9,10...…”