Supramolecular Assemblies with Aggregation-Induced Emission Properties for Sensing and Detection

The fabrication of new supramolecular materials for real-time detection of analytes including ions, organic pollutants, gases, biomolecules, and drugs is of pivotal importance in industrial manufacture, clinical treatment, and environmental remediation. Incorporating fluorescent molecules with distinct aggregation-induced emission (AIE) effects into supramolecular assemblies has received much attention over the past two decades, owing to the remarkable performance of the AIE-active supramolecular materials in sensing and detection. In this minireview, we summarize the recent progress of superior detection systems on the basis of supramolecular assemblies accompanied with AIE features. We envision that this minireview will be helpful and timely for relevant researchers to stimulate new thinking for constructing new AIE-based supramolecular materials with advanced architectures for effective sensing and detection.     

Vesicles displaying aggregation-induced emission: Fabrication and applications

Vesicles displaying aggregation induced emission are very promising in fields related to biology. In this review, we summarized recent progresses in the creation of such vesicles and their applications. The following contents are included: 1) the general background of AIE vesicles; 2) creation of AIE vesicles with synthetic covalent compounds; 3) creation of AIE vesicles with supramolecular chemistry; 4) the application of AIE vesicles in real-time imaging, visualized drug delivery, cell communication and fission-fusion process, and light-harvesting. Finally, we envision AIE vesicles may have profound impact on medical science, biological science and material science.     

New tetraphenylpyridinium-based luminogens with aggregation-induced emission characteristics

The research on aggregation-induced emission (AIE) has drawn increasing interests in the past decade. With the efforts scientists paid, a variety of AIE systems have been developed, among which the tetraphenylethelene and silole derivatives are the most studied. Development of new AIE systems could further enrich the AIE molecules and promote the development of AIE area. In this communication, we prepared a new AIE system based on 1,2,4,6-tetraphenylpyridinium ions according to the restriction of intramolecular rotation mechanism. These molecules could be facilely synthesized via one-step and one-pot reaction. The ionic AIE-active molecules could find wide application in sensing and optoelectronic areas.     

Progress and trends in self-assembly driven fluorescent organic nanoparticles: A brief overview

Organic nanoparticles have recently attracted increasing attention in diverse field of applications in materials, sensing, biomedicine and others due to their extraordinary physico-optical properties and facile synthesis. These π-conjugated small organic molecules exhibit aggregation induced emission (AIE) property, photo/physical stability, good cytocompatibility as well as biodegradability and easy surface modulation ability. In this mini-review, we have summarized the progress and trends in the area of development of organic nanoparticles from π-conjugated small organic molecule. Some typical as well as few unconventional examples of AIE active systems are discussed and also focussed on their structure-property relationship to exhibit unique photophysical characteristics. To decipher the mechanistic aspect of AIE phenomenon, systematic structural design strategies are also discussed. Finally, development of optoelectronic devices, sensors, bioimaging probes, therapeutic agents, and AIE-active luminogens are exemplified with high tech innovations.     

A fluorescent supramolecular crosslinked polymer gel formed by crown ether based host-guest interactions and aggregation induced emission

Based on the combination of B21C7/dialkylammonium salt host-guest interactions and tetraphenylethylene(TPE)-based aggregation-induced emission(AIE) effect, a fluorescent supramolecular crosslinked polymer gel was successfully prepared. Compared with the solution of TPE-containing small molecules, this gel exhibited remarkable fluorescence enhancement due to the AIE effect of TPE units. The "gelation induced fluorescence emission" phenomenon can be explained by the hindered intramolecular rotation of phenyl rings of TPE. Because of the reversibility and stimuli-responsiveness of the B21C7/dialkylammonium salt host-guest interactions, the transition between the fluorescent supramolecular crosslinked polymer gel and the disassembled sol with very weak fluorescence can be realized by adding p H and thermal stimuli. This novel material contributes to the development of supramolecular chemistry, polymer science and fluorescent materials and offers a new method to construct functional supramolecular materials.     

“Aggregation-induced emission” of transition metal compounds: Design,mechanistic insights,and applications

In the last decades, compounds with ‘Aggregation-Induced Emission’ (AIE), which are weakly or non-emissive at all in solution but exhibit a strong luminescence in aggregated states, have emerged as an extraordinary breakthrough in the field of luminescent materials, allowing to circumvent ‘Aggregation Caused Quenching’ (ACQ), which in many cases prevents the development of efficient solid-state materials for optoelectronic applications.Since the discovery of AIE, many AIE-active materials have been developed, most of them composed of organic molecules, and thus fluorescent in nature. Although a wide range of applications such as bioimaging, sensing, multi-stimuli responsive materials, and optoelectronic devices have been proposed for this new class of materials, triplet harvesting phosphorescent materials have much longer lifetimes as compared to their singlet harvesting analogues, and for this particular reason, the development of AIE-active phosphorescent materials seems to be a promising strategy from the applications point of view. In this respect, the synthesis of new AIE-active systems including heavy metals that would facilitate the population of low-lying excited triplet states via spin-orbit coupling (SOC), for which the strength increases as the fourth power of atomic number, i.e. Z⁴, is highly desirable. This review covers the design and synthetic strategies used to obtain the AIEgens reported in the literature that contain either d-block metals such as Cu(I), Zn(II), Re(I), Ru(II), Pd(II), Ir(III), Pt(II), Au(I), and Os(IV), describing the mechanisms proposed to explain their AIE. New emerging high-tech applications such as OLEDs, chemical sensors or bioimaging probes proposed for these materials are also discussed in a separate section.     

Divergent and Stereoselective Synthesis of Tetraarylethylenes from Vinylboronates

The synthesis of a new tetraborylethylene (TBE) is reported, and its application in the preparation of [4+0]-tetraarylethenes (TAEs) is elucidated. TAEs have widespread applications in material science and supramolecular chemistry due to their aggregation-induced emission (AIE) properties. The divergent and stereoselective synthesis of [3+1]-, [2+2]-, and [2+1+1]-TAEs via multiple couplings of vinylboronates with aryl bromides is demonstrated. These couplings feature a broad substrate scope and excellent functional group compatibility due to mild reaction conditions. Facile access to various tetraarylethenes is provided. This strategy represents an important complement to the conventional methods employed for the synthesis of TAEs, and would be a valuable tool for synthesizing TAE-based molecules useful in functional materials, biological imaging and chemical sensing.     

Progress of 3-aminopyridine-based amide,urea, imine and azo derivatives in supramolecular gelation

Supramolecular gels derived from low molecular weight gelators are considered to be fascinating soft and smart materials. Gelators of this class form gel networks involving noncovalent interactions and show various applications in many areas. The structural softness and the arrangement of the gelator molecules in the aggregated state have the collaborative effect to intensify the properties of the molecules for their potential applications in material chemistry. Of the various properties, stimulus responsibility is a desired property of supramolecular gel that finds profound application in sensing. In this review, a comprehensive summary of the work on 3-aminopyridine-based amide, urea, imine and azo gelators of different architectures indicating their different uses in supramolecular chemistry has been focused.     

具有聚集诱导发光性质的近红外荧光染料

聚集诱导发光(AIE)现象的发现为解决传统有机荧光分子在高浓度和聚集形态下存在的荧光猝灭问题提供了最佳方案,并实现了在光电器件、化学传感、生物成像和靶向治疗等众多领域的广泛应用.随着对AIE 发光机理研究的不断深入,AIE 分子体系得到了极大的扩展.其中,一类具有给体-受体结构的AIE分子能够显著降低分子能隙,使发光分...     

Self‐Assembly of Aggregation‐Induced‐Emission Molecules

The last decade has witnessed rapid developments in aggregation‐induced emission (AIE). In contrast to traditional aggregation, which causes luminescence quenching (ACQ), AIE is a reverse phenomenon that allows robust luminescence to be retained in aggregated and solid states. This makes it possible to fabricate various highly efficient luminescent materials, which opens new paradigms in a number of fields, such as imaging, sensing, medical therapy, light harvesting, light‐emitting devices, and organic electronic devices. Of the various important features of AIE molecules, their self‐assembly behavior is very attractive because the formation of a well‐defined emissive nanostructure may lead to advanced applications in diverse fields. However, due to the nonplanar topology of AIEgens, it is not easy for them to self‐assemble into well‐defined structures. To date, some strategies have been proposed to achieve the self‐assembly of AIEgens. Herein, we summarize the most recent approaches for the self‐assembly of AIE molecules. These approaches can be sorted into two classes: 1) covalent molecular design and 2) noncovalent supramolecular interactions. We hope this will inspire more excellent work in the field of AIE.     

Recent Advances of AIE-Active Conjugated Polymers: Synthesis and Application

Conjugated polymers (CPs) have long been recognized as an important class of materials. The highly conjugated backbone of the CPs will facilitate the rapid exciton migration and result in amplification of fluorescence signals. However, CPs are likely to aggregate and form excimers in solid states, directly leading to the fluorescence quenching, namely aggregation-caused quenching (ACQ), hence inhibiting their prospective utilizations in a large degree. Since the effect of aggregation-induced emission (AIE) is opposite to that of notorious ACQ, the AIE has raised great attention from scientists. CPs with AIE or aggregation-enhanced emission (AEE) features may help to solve the ACQ problem and meanwhile impart polymers with new properties and practical applications. In this review, we summarize the recent progress on the preparation of CPs with AIE or AEE characteristics, where AIE-active luminogens are located at polymer backbones or pendants. Their potential applications including fluorescent sensors, biological probes, and active layers for the fabrication of light-emitting diodes are also described.     

New sensing mechanisms for design of fluorescent chemosensors emerging in recent years

During the past decade, fluorescent chemosensors have become an important research field of supramolecular chemistry and have attracted great attention because of their simplicity, high selectivity and sensitivity in fluorescent assays. In the design of new fluorescent chemosensors, exploration of new sensing mechanisms between recognition and signal reporting units is of continuing interest. Based on different photophysical processes, conventional sensing mechanisms including photo-induced electron transfer (PET), intramolecular charge transfer (ICT), metal-ligand charge transfer (MLCT), twisted intramolecular charge transfer (TICT), electronic energy transfer (EET), fluorescence resonance energy transfer (FRET), and excimer/exciplex formation have been investigated and reviewed extensively in the literature. This tutorial review will mainly focus on new fluorescent sensing mechanisms that have emerged in the past five years, such as aggregation-induced emission (AIE) and C=N isomerization, which can be ascribed to fluorescence changes via conformational restriction. In addition, excited-state intramolecular proton transfer (ESIPT) has not been well reviewed yet, although a number of chemosensors based on the ESIPT mechanism have been reported. Thus, ESIPT-based chemosensors have been also summarized in this review.     

AIE-active polymers for explosive detection

Super-sensitive and ultra-selective detection of explosives plays a crucial role in anti-terrorism operations, homeland security, civilian safety and environment protection. Among the developed fluorescent probes, the polymers with aggregation-induced emission (AIE) characteristics have drawn much attention due to their bright emission in the aggregate and solid states. However, no review has summarized the development of AIE-active polymers for explosive detection. Herein, we reviewed the recent progress on using AIE-active polymers to detect explosives with super-amplification quenching effect. Moreover, the challenges and opportunities in this area were also briefly discussed.     

超分子有机膦大环化合物研究进展

有机膦大环化合物是伴随着大环化学的出现而发展起来的．它们不仅具有多变的结构而且非常稳定;不仅能够包结客体分子,还可以与许多过渡金属形成稳定的配位化合物,在主客体化学以及金属有机催化领域中受到人们的广泛关注．由于其独特的性质,有机膦大环化合物在超分子化学的发展中具有重要的地位．本文主要介绍了近些年有机膦大环化合物研究的新进展及其在超分子化学中的应用．     

Supramolecular nano drug delivery systems mediated via host-guest chemistry of cucurbit[n]uril (n = 6 and 7)

As a novel family of macrocyclic molecules,cucurbit[n]urils(CB[n]s) have emerged as promising building blocks of supramolecular nano drug delivery systems(SNDDS) in recent years.Direct encapsulation of amphiphilic guests by CB[6] and CB[7] can modulate their amphiphilicity,resulting in formation of supramolecular amphiphiles that self-assemble into supramolecular nanoparticles for drug delivery.Additionally,CB[n]'s host-guest chemistry on the surface of mesoporous nanoparticles makes CB[n] an ideal blocking agent to control drug release from delivery vehicles.These SNDDS possess intrinsic stimuli responsiveness towards external guest or host,which can further incorporate re s ponsiveness to a variety of other stimuli including pH,thermal,redox,photo and enzyme,to realize multiple stimuli-responsive drug release.Moreover,the recent breakthrough in direct functionalization of CB[n]s has provided a feasible method for preparing superior CB[6] and CB[7] derivatives that can be employed to build multifunctional SNDDS with unoccupied macrocycles located on surface,which could be decorated with various functional "tags" through host-guest chemistry.In this review,we summarized the recent progress of CB[6] and CB[7] based SNDDS through formation of supramolecular amphiphiles,supramolecular nanovalves as well as supramolecularly tailorable surface,which we hope to further promote the development of CB[n]s family as building blocks for advanced SNDDS.     

Fluorescent Dynamic Covalent Polymers for DNA Complexation and Templated Assembly

Dynamic covalent polymers (DCPs) offer opportunities as adaptive materials of particular interest for targeting, sensing and delivery of biological molecules. In this view, combining cationic units and fluorescent units along DCP chains is attractive for achieving optical probes for the recognition and delivery of nucleic acids. Here, we report on the design of acylhydrazone-based DCPs combining cationic arginine units with π-conjugated fluorescent moieties based on thiophene-ethynyl-fluorene cores. Two types of fluorescent building blocks bearing neutral or cationic side groups on the fluorene moiety are considered in order to assess the role of the number of cationic units on complexation with DNA. The (chir)optical properties of the building blocks, the DCPs, and their complexes with several types of DNA are explored, providing details on the formation of supramolecular complexes and on their stability in aqueous solutions. The DNA-templated formation of DCPs is demonstrated, which provides new perspectives on the assembly of fluorescent DCP based on the nucleic acid structure.     

On sombor indices of tetraphenylethylene,terpyridine rosettes and QSPR analysis on fluorescence properties of several aromatic hetero-cyclic species

Aromatic heterocyclic compounds have received a lot of interest due to their various important medicinal and biological applications. The broad synthetic investigation and functional usefulness of heterocyclic molecules is driving a surge in research interest. They are found in more than 90% of innovative medications and bridge the gap between biology and chemistry, where so much scientific discovery and application happens. Heterocycles are also useful in a variety of domains, including pharmaceutical chemistry, biochemistry, and others. In this article, quantitative structure-property relationship (QSPR) models is developed using sombor indices to predict fluorescence properties of aromatic hetero-cyclic species based on their structural features. This allows researchers to estimate the fluorescence behavior of new molecules without performing experimental measurements. As an application, we have computed the sombor indices for self-assembled supramolecular graphs made of terpyridine (TPE) and tetraphenylethylene (TPY) molecules that are produced as rosette cycles. This form of rosettes graph is used in electrical sensors, light emitting diodes, bioimaging and photoelectric devices, and so on. Tetraphenylethylene can be used to make fluorescent probes for next-generation sensing applications with typical induced aggregative emission behavior.     

具有聚集诱导发光特性的四苯基乙烯研究进展

具有聚集诱导发光(aggregation-induced emission,AIE)性质的四苯基乙烯及其衍生物(tetraphenylethenes,TPEs)因其发光性能优良、合成简便、易多功能化而越来越受到关注.本文着重对最近几年TPEs的AIE性质研究进展进行综述.在阐述结构与AIE性质之间关系的同时,介绍了TPEs在生物、化学传感器及其它方面的应用, 并对TPEs的设计与应用给予展望.     

Aggregation-induced emission of siloles

Aggregation-induced emission (AIE) is a unique and significant photophysical phenomenon that differs greatly from the commonly acknowledged aggregation-caused emission quenching observed for many π-conjugated planar chromophores. The mechanistic decipherment of the AIE phenomenon is of high importance for the advance of new AIE systems and exploitation of their potential applications. Propeller-like 2,3,4,5-tetraphenylsiloles are archetypal AIE-active luminogens, and have been adopted as a core part in the design of numerous luminescent materials with diverse functionalities. In this review article, we elucidate the impacts of substituents on the AIE activity and shed light on the structure–property relationship of siloles, with the aim of promoting the judicious design of AIE-active functional materials in the future. Recent representative advances of new silole-based functional materials and their potential applications are reviewed as well.     

Chiral assembly of organic luminogens with aggregation-induced emission

Chirality is important to chemistry, biology and optoelectronic materials. The study on chirality has lasted for more than 170 years since its discovery. Recently, chiral materials with aggregation-induced emission (AIE) have attracted increasing interest because of their fascinating photophysical properties. In this review, we discussed the recent development of chiral materials with AIE properties, including their molecular structures, self-assembly and functions. Generally, the most effective strategy to design a chiral AIE luminogen (AIEgen) is to attach a chiral scaffold to an AIE-active fluorophore through covalent bonds. Moreover, some propeller-like or shell-like AIEgens without chiral units exhibit latent chirality upon mirror image symmetry breaking. The chirality of achiral AIEgens can also be induced by some optically active molecules through non-covalent interactions. The introduction of an AIE unit into chiral materials can enhance the efficiency of their circularly polarized luminescence (CPL) in the solid state and the dissymmetric factors of their helical architectures formed through self-assembly. Thus, highly efficient circularly polarized organic light-emitting diodes (CPOLEDs) with AIE characteristics are developed and show great potential in 3D displays. Chiral AIEgens are also widely utilized as “turn on” sensors for rapid enantioselective determination of chiral reagents. It is anticipated that the present review can entice readers to realize the importance of chirality and attract much more chemists to contribute their efforts to chirality and AIE study.

This review highlights the recent development of chiral materials with aggregation-induced emission properties, including their molecular structures, self-assembly and functions.