Nonconventional macromolecular luminogens with aggregation-induced emission characteristics

Nonconventional luminogens without classic conjugated structures have drawn increasing interests owing to their fundamental importance and promising applications. These luminogens generally bear such subgroups as tertiary amine, C = C, C≡N, C = O, OH, ether, and imide. The emission mechanism, however, remains under debate. Different assumptions like oxidation or acidification of tertiary amines, aggregation of C = O groups, as well as clustering and electron cloud overlap are proposed. Unlike concentration quenching and aggregation-caused quenching (ACQ) that are normally observed in traditional luminogens, many of these unorthodox luminogens exhibit unique aggregation-induced emission (AIE) characteristics, regardless of their molecular architectures. This review summarizes varying unorthodox luminogens with AIE features, aiming to outline the recent advances in this exciting area, with focus on the macromolecular systems. In light of the reported results, clustering-triggered emission mechanism, namely clustering of diverse subgroups with subsequent electron cloud overlap and conformation rigidification can well rationalize the photophysical behaviors of most systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 560–574     

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.     

Preparation and self-assembly of amphiphilic polymer with aggregation-induced emission characteristics

An amphiphilic polymer bearing tetraphenylethene (TPE) moiety was synthesized by convenient reactions. The polymer exhibits unique aggregation-induced emission (AIE) characteristics and can self-assemble to size-tunable particles in DMF/water mixtures. The polymer nanoparticles can be used for cell imaging, which provides a potential stable fluorescent tool to monitor the distribution of drugs and bioconjugates in living cells.     

压致变色聚集诱导发光材料

聚集诱导发光化合物分子具有特殊的螺旋桨形扭曲构象结构, 导致其很难在结晶状态下进行紧密堆砌, 使得其结晶结构容易在外力的作用发生改变, 致使其分子能级水平和发光光谱发生变化, 产生压致发光变色现象. 因此, 聚集诱导发光化合物是压致发光变色材料的一个重要来源. 压致变色聚集诱导发光材料是一类重要的压致发光变色材料, 其既具有压致发光变色的性能, 又具有聚集诱导发光的性能. 它是一类智能材料, 在应力传感、商标防伪和发光器件等领域具有重要的潜在应用, 近年来受到人们极大的关注. 本文分类介绍了近年来压致变色聚集诱导发光材料的研究进展.     

α-吡喃酮衍生物的合成及聚集荧光增强性质研究

设计合成了具有4个苯基取代的α-吡喃酮衍生物,研究了该化合物在溶液中的稳态光物理过程,以及在四氢呋喃/水混合溶剂中的聚集行为和发光性质.该化合物在良溶剂中几乎没有发光,而形成聚集体后发出明亮的蓝绿色荧光,荧光量子产率达17%,比溶液中增强了253倍.根据化合物的结构和低温荧光实验结果推断,聚集荧光增强主要是聚集体中分子...     

Facile synthesis of poly(aroxycarbonyltriazole)s with aggregation-induced emission characteristics by metal-free click polymerization

Regioseletive 1,3-dipolar polycycloadditions of 4,4'-isopropylidenediphenyl dipropiolate (1) and tetraphenylethene (TPE)-containing diazides (2) are carried out in polar solvents such as DMF/toluene at a moderate temperature of 100℃ for 6 h,producing poly(aroxycarbonyltriazole)s (PACTs) P3 with high molecular weights (Mw up to 23900) and regioregularities (F1,4 up to ～90%) in high yields (up to ～99%).These metal-free click polymerizations can propagate smoothly in an open atmosphere without protection from ...     

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.     

含磷酰杂菲苯甲酸对苯二酯的聚集诱导发光增强性能及其在检测过渡金属离子中的应用

有机化合物因成膜以后荧光淬灭而使其应用受到很大限制, 所以研究、开发能在聚集状态下呈现优异发光性能的新材料就尤为重要. 由于分子间π-π和极性共同相互作用, 使得磷酰杂菲环的转动受到限制, 从而使苯甲酸-2-[6-氧化-6-氢-二苯基(c,e)＜1,2＞氧杂磷酰基]-1,4-二羟基苯二酯(OP)在达到一定规整聚集程度时, 荧光强度成倍增加, 具有了聚集诱导发光增强(AIEE)性质. 实验结果表明: 浓度低于1×10^－6 mol•L^－1 的OP会失去AIEE性质; 浓度为1×10^－4 mol•L^－1的Hg^2＋, Fe^2＋和 Fe^3＋会分别淬灭浓度为1×10^－5 mol•L^－1 OP荧光强度的26%, 34%, 74%, 而Pb^2＋, Zn^2＋, Cd^2＋, Co^2＋, Mn^2＋, Cu^2＋, Ni^2＋, Ag^＋等离子的淬灭效率却很低, 这一性质表明该化合物可以用作过渡金属离子的特异性检测材料.     

Theoretical study on the aggregation-induced emission mechanism of anthryl-tetraphenylethene

Since the concept of aggregation-induced emission (AIE) was proposed by Benzhong Tang's research group in 2001, the exploration of the mechanism of AIE and the development of new high-performance AIE materials have been the focus and goal of this field. On the basis of a large number of experiment results, AIE mechanism has been well explained by lots of works, such as restricted intramolecular motion (RIM), J-aggregate et al. As tetraphenylethlene (TPE) molecules are stacked, the rotation of the benzene ring rotor is blocked, and the energy attenuation is released in the form of radiation, showing the AIE effect. In order to further explore the AIE effect of TPE, we performed electronic structure, spectrum simulation, and AIE mechanism calculations of the anthryl-tetraphenylethene (TPE-an) monomer and dimer in the gas phase, tetrahydrofuran (THF), and aqueous solutions at the B3LYP/6-31G** level. The calculation results show that TPE-an molecule is in a propeller-like configuration, and its fluorescence intensity is weak; compared with the monomer, the fluorescence intensity of the dimer increases by 87% in aqueous solution; the fluorescence intensity in the gas phase, THF solution, and aqueous solution gradually enhances with the increase of the degree of aggregation, which are consistent with the experimental results. The enhancement of fluorescence intensity is caused by the change of molecular structure caused by aggregation. This detailed AIE luminescence mechanism will provide theoretical guidance for AIE material design.     

聚集诱导发光

聚集诱导发光(AIE)是唐本忠院士于2001年提出的一个科学概念,是指一类在溶液中不发光或者发光微弱的分子聚集后发光显著增强的现象。高效固态发光的AIE材料有望从根本上解决有机发光材料面临的聚集导致发光猝灭难题,具有重大的实际应用价值。从分子内旋转受限到分子内运动受限,从聚集诱导发光到聚集体科学,AIE领域已经取得了许多原创性的成果。在本综述中,我们从AIE材料的分类、机理、概念衍生、性能、应用和挑战等方面讨论了AIE领域最近取得的显著进展。希望本综述能激发更多关于分子聚集体的研究,并推动材料、化学和生物医学等学科的进一步交叉融合和更大发展。     

三种席夫碱聚集荧光增强性质及构效关系的研究

通过水杨醛和苯二胺反应合成了三种具有聚集荧光增强性质的分子,运用1H-NMR对其结构进行了表征。在乙醇-水混合溶液中采用荧光光谱法进行了聚集荧光增强性质的测试,结果表明,三种分子均具有聚集荧光增强性质,构效关系不同,对分子识别能力也不同。在水溶液中,水杨醛能够与对苯二胺原位形成具有聚集荧光增强性质的席夫碱,实现了对苯二胺原位识别;而N,N'-二水杨醛缩间苯二胺却表现出对金属Zn2+选择性检测。     

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.     

Naphthalene diimide based near-infrared luminogens with aggregation-induced emission characteristics for biological imaging and high mobility ambipolar transistors

Organic conjugated materials combining high conductivity with strong solid-state emission are highly desired for organic electronic applications, yet still rather rare. Herein, a novel luminogen(TEN) comprised by linking naphthalene diimides and triphenyl ethylene with vinyl bridges is reported. TEN exhibits aggregation-induced emission(AIE) behavior of a strong nearinfrared fluorescence over 700 nm and the efficiency above 60.5% in the solid state, while also shows promising application in vivo bio-imaging with good permeability and extremely low background. Single crystal of TEN reveals intra-and intermolecular C–H···O hydrogen bonds, contributing to an inclined molecular stacking along the a-axis of the cell, creating a 1 D charge carrier transporting channel under a short π-π interaction distance of 3.42 ?, which might benefit the solid emission and charge transport ability simultaneously. Solution processed bottom contact, top gate organic field effect transistors based on TEN reveal a high ambipolar charge transport ability with the hole mobility up to 0.13 cm~2 V~(-1) s~(-1) and electron mobility up to0.010 cm~2 V~(-1) s~(-1). Further atomic force microscopy and X-ray diffraction analysis on TEN thin film confirm the existence of the1 D π-π stacking channel, suggesting the stacking geometry revealed in crystal crucial for facilitating high charge carrier mobility while preserving the strong solid emission at the same time.     

1-（（12-Bromododecyl）oxy）-4-（（4-（4-pentylcyclohexyl） phenyl）ethynyl） benzene：Liquid crystal with aggregation-induced emission characteristics

The luminescent liquid crystals （LLCs） are expected to solve the conflicts between the aggregation caused quenching and the requirement of aggregation or self-organization for LCs. Herein, we developed a new strategy of applying aggregation-induced emission （AIE） phenomenon to the molecular design of LCs towards LLCs. In this report, a calamitic liquid crystal based on tolane with AIE characteristics was successfully synthesized and the chemical structure was characterized by 1H, 13C NMR, and matrix-assisted laser desorption/ionization time-of-flight （MALDI-TOF） high-resolution mass spectra. The fluorescence behavior was studied by fluorescence spectroscopy and the liquid crystal phase behaviors were investigated by differential scanning calorimetry （DSC）, polarized optical microscopy （POM）. The crystal structure was obtained by X-ray diffraction crystallography with P1 space group. Results demonstrated that the sample was AIE active and the LC phases sequence during cooling was nematic, smectic C and smectic B phase.     

1,1‐Diphenylvinylsulfide as a Functional AIEgen Derived from the Aggregation‐Caused‐Quenching Molecule 1,1‐Diphenylethene through Simple Thioetherification

An efficient and readily scalable thioetherification between 1,1‐diphenylethene (DPE) and sodium arylsulfinate was developed for the synthesis of 1,1‐diphenylvinylsulfide (DPVS) with the yield up to 99 %. The photophysical properties of DPVS show that the introduction of arylsulfenyl groups onto the parent molecule DPE makes DPVS a novel type of aggregation‐induced emission (AIE) luminogen (AIEgen) with large Stoke's shift (up to 188 nm). These DPVS possess AIE properties due to restriction of intramolecular motions (RIM), as demonstrated by crystal structure analysis. Importantly, the AIE performance of DPVS can be applied to sense the nitroaromatic explosive picric acid in aqueous systems through a “turn‐off” response.     

Detection of the critical micelle concentration of cationic and anionic surfactants based on aggregation-induced emission property of hexaphenylsilole derivatives

We report a fluorescence “turn-on” method to detect the critical micelle concentration (CMC) of surfactants. This method works well for both cationic and anionic surfactants. It employs an unprecedented mechanism (aggregation-induced emission, or AIE) to determine the CMC values, and the results are consistent with the data obtained by the classical techniques. In addition, this method renders the convenient detection of the CMC values. Any large and professional instruments are unnecessary, instead, a portable UV lamp and an ultrasonic generator are enough to carry out the detection in an ordinary laboratory. Considering that micelles are interesting entities and have found applications in many important fields such as emulsion polymerization, template of nanosized materials synthesis, controllable drug delivery and macromolecular self-assembling. Our experimental results may offer a facile, sensitive and promising method to detect the formation of micelles constructed by the new amphiphilic molecules and macromolecules. Supported by the National Natural Science Foundation of China (Grant Nos. 50573065 & 50873086) and the Natural Science Foundation of Zhejiang Province (Grant No. Z406018)     

Host–guest interaction-mediated fabrication of aggregation-induced emission supramolecular hydrogel for use as aqueous light-harvesting systems

ABSTRACT

Aqueous light-harvesting systems in hydrogels formed by specific noncovalent interactions exhibit both solution and solid-state performance. In this work, the copolymerisation of acrylamide (AM), 4-(1,2,2-triphenylvinyl) phenyl acrylate (vTPE), and guest units 1-benzyl-3vinylimidazolium (G) was carried out with initiator to form P(AM-vTPE-G). Then, supramolecular hydrogels were fabricated by dynamic host–guest interactions the guest unit and host molecule cucurbit[8]uril (CB[8]). The aggregated tetraphenylethylene (TPE) moieties in the polymer chains aggregate together, possessed high fluorescence enhancement during the cross-linking process. Meanwhile, emission characteristics of the obtained aqueous light-harvesting systems were further examined by using the donor (supramolecular hydrogel) and acceptor (Eosin Y disodium salt) system. The process provides a novel method for the production of fluorescence and self–healing supramolecular hydrogel with various potential applications.     

Luminescent core–shell nanoparticles with crosslinked aggregation-induced emission core structures: Emission both in solution and solid states

Luminescent core–shell nanoparticles (NPs) with crosslinked aggregation-induced emission (AIE) core structures, which exhibited excellent emission independent of the dispersion state of the NPs, have been developed by a facile one-pot method based on the self-assembly of an amphiphilic block copolymer poly(PEGMA)-b-poly(DB3VT). Core–shell micelles with a poly(DB3VT) core were formed from poly(PEGMA)-b-poly(DB3VT) in tetrahydrofuran (THF)/H₂O condition, and the crosslinked AIE-based structure was selectively incorporated into the core by the Suzuki coupling reaction between poly(DB3VT) blocks and tetraphenylethylene (TPE)-based coupling monomers at the same time. This method afforded a uniform NP with a crosslinked TPE-based AIE core structure. The obtained NP exhibited excellent emission both in diluted solution and solid states. This result indicated that the formed TPE-based AIE core structure was always aggregated regardless of NP dispersion owing to the crosslinking as we expected. The crosslinked TPE-based AIE core structure, which was related to the emission property, was readily tuned by the selection and combination of coupling monomers in the Suzuki coupling reaction. By incorporating electron-deficient units into the core, the emission color could be successfully tuned from yellow-green to orange and red while maintaining the emission property independent of the state of the NP dispersion. These results demonstrated that NPs with the crosslinked AIE core structures are a promising luminescent material design motif to realize emission independent on molecular dispersion.     

Piezofluorochromism of triphenylamine-based triphenylacrylonitrile derivative with intramolecular charge transfer and aggregation-induced emission characteristics

New triphenylacrylonitrile derivative (DPPA) with triphenylamine moiety as electron donor group has been synthesized. Its emission wavelengths were strongly affected by solvent polarity, indicating intramolecular charge transfer (ICT) transitions. It was found that DPPA was almost non-emissive in tetrahydrofuran (THF), and the emission could be intensified obviously when a great amount of H₂O was added, illustrating aggregation induced emission property. It is interesting that the pristine crystal of DPPA emitted green light, and the ground made its emitting color to change into orange, which could be recovered under fumed with dichloromethane (DCM) vapor. The piezofluorochromic behavior might be switched reversibly under the stimulus of external force because of crystalline-amorphous phase transformation, which could be confirmed from the results of PXRD patterns and DSC curves in different solid states. This work might open a new strategy to provide a broad perspective for the development of AIE PFC materials.     

Biothiol-specific fluorescent probes with aggregation-induced emission characteristics

Biothiols are important species in physiological processes such as regulating protein structures, redox homeostasis and cell signalling. Alternation in the biothiol levels is associated with various pathological processes, therefore non-invasive fluorescent probes with high specificity to biothiols are highly desirable research utilities. Meanwhile, fluorescent probes with aggregation-induced emission properties (AIEgens) possess unique photophysical properties that allow modulation of the sensing process through controlling the aggregation-disaggregation or the intramolecular rotational motions of the fluorophores. Herein we review the recent progress in the development of biothiol-specific AIEgens. In particular, the molecular design principles to target different types of biothiols and the corresponding sensing mechanisms are discussed, along with the potential of the future design and development of multi-functional bioprobes.