AIE Properties Research Articles

Theoretical study on the mechanism of hot excitons combined with aggregation-induced emission in efficient red fluorescent molecules.

Fluorescent emitters with the hot exciton mechanism combined with aggregation induced emission (AIE) character show prospective applications in organic light emitting diodes (OLEDs). However, theoretical studies on amorphous states are limited. In this work, a theoretical study is performed on the photophysical properties of the reported compound 4-(7-(10-ethyl-10H-phenothiazin-3-yl)benzo[c][1,2,5]thiadiazol-4-yl)-N,N-diphenylaniline (PBTPA), which possesses a hot exciton mechanism and AIE. The aggregation states of this molecule in a film are given by molecular dynamics (MD) simulations, and then the photophysical properties are studied by using the QM/MM method with the consideration of the solid-state effect (SSE). The results explain the hot exciton and AIE mechanism of the molecule. First, there is a hot exciton channel between the S1 and T2 state of the PBTPA. Second, the conformational changes of PBTPA between the ground state and the excited state are restricted in the aggregate state. Last, in the low frequency region, the rotation motion is suppressed, and then the reorganization energy and Huang-Rhys (HR) factor in the aggregate state are much smaller. Therefore, the molecules show strong fluorescence efficiency in the aggregated state.

Visual organophosphate vapor sensing by dibenzylidine derivatives exhibiting intramolecular charge transfer and aggregation induced emission

Three DBA derivatives containing different electron donor and acceptor units display both ICT and AIE properties. The intriguing optical features of the molecules have been employed for selective, high sensitivity detection of organophosphate vapors.

Thermally Activated Delayed Fluorescence Dendrimers with Aie Property and Functional Dendrons for High-Efficiency Solution-Processed White Oleds

Thermally Activated Delayed Fluorescence Dendrimers with Aie Property and Functional Dendrons for High-Efficiency Solution-Processed White Oleds

1]Benzothieno[3,2-b][1]benzothiophene-based dyes: effect of the ancillary moiety on mechanochromism and aggregation-induced emission.

It is an established fact that [1]benzothieno[3,2-b][1]benzothiophene (BTBT) is a champion molecule for high-mobility OFET devices. Recently, it has also been utilized in dye-sensitized solar cells (DSSCs) and organic photovoltaics (OPVs) as an alternative to fullerene (non-fullerene acceptor). Considering the advantageous features of BTBT, we herein report its aggregation-induced emission (AIE) and mechanofluorochromic (MFC) behaviour for the first time. We have designed and synthesized two new BTBT derivatives: [1]benzothieno[3,2-b][1]benzothiophene-tetraphenylethylene (BTBT-TPE) and [1]benzothieno[3,2-b][1]benzothiophene-phenyl-N,N-dimethylamine (BTBT-NMe). The donor-π-acceptor-π-donor-integrated BTBT-TPE showed AIE whereas BTBT-NMe showed aggregation-caused quenching (ACQ), as evident by their quantum yield and lifetime results. BTBT-NMe was found to possess great interaction, resulting in the halochromic (protonation) effect. The theoretical calculation of the electronic distribution and energy investigation were consistent with the experimental outcomes. The electron contribution of the HOMO is high for BTBT-NMe at the donor, which can be attributed to the weaker donating nature of TPE compared to that of the NMe group. Overall, the results indicate the potential of the mechanical stimuli and aggregation response of the studied compounds for further investigation.

Ligand-regulated three-photon AIE properties of manganese(II) complexes for photodynamic therapy.

Owing to the advantages of deeper penetration depth and lower biological damage, multi-photon AIE probes are widely used in the field of multi-photon therapy. We have developed a series of carbazole terpyridine manganese(II) complexes (MD1-MD3) that are promising as aggregation-induced emission (AIE) photosensitizers (PSs). MD1-MD3 exhibit excellent three-photon AIE properties in DMSO/H2O solution. We modulated the AIE properties of the Mn(II) complexes by introducing halogen atoms (Br/I). The three-photon fluorescence intensity of the complexes upon introducing halogen atoms is strong under the conditions of fw = 99% and 60%, respectively. Based on halogen-substituted carbazole ligands, MD3 can be applied as a multi-photon absorption photosensitizer which can produce 1O2 and O2˙-. MD3 damages the mitochondrial morphology, leads to a decrease in mitochondrial membrane potential, and then triggers the apoptosis of cancer cells. Furthermore, MD3 is successfully applied as a photosensitizer in tumor theranostics in vivo. This work provides a new idea for ligand modulation of multiphoton AIE ground state transition metal complexes to make them multiphoton therapeutic agents.

Enhanced cocatalyst-free photocatalytic H2 evolution by the synergistic AIE and FRET for an Ir-complex conjugated porphyrin

A new Ir-complex conjugated porphyrin exhibits AIE property for the Ir-complex unit, inhibition of ACQ of the porphyrin unit and efficient energy transfer from the Ir-complex to the porphyrin, therefore, enhanced photocatalytic H2 evolution.

18α-Glycyrrhetinic acid aggregation-induced emission probes for visual fluorescence detection of explosive as well multi-functional applications

Two novel compounds with good AIE properties were synthesized. As fluorescent probes, these compounds could effectively and quickly detect the explosive FOX-7.

Tetraphenylethene functionalized quinoxaline derivative exhibiting aggregation-induced emission and multi-stimuli responsive fluorescent switching

A new tetraphenylethene functionalized quinoxaline derivative TPVSQ has been synthesized using classical Knoevenagel condensation reaction. Spectral study and quantum chemical calculation indicated that it possessed D-π-A molecular structure. TPVSQ exhibited typical ICT (intramolecular charge transfer) transition and AIE property. Interestingly, TPVSQ also showed multi-stimuli responsive behavior. The emission spectra of TPVSQ could be switched in response to not only mechanical grinding and solvent fuming but also the protonation effect. The responsive mechanism has been studied and explained. The current work provided a strategy for the molecular design of new multi-stimuli responsive materials.

Fluorescence probe with AIE properties for ratiometric/turn off detecting of water in organic solvents and solid state

ABSTRACT Efficient detection of trace water was important before use in water-sensitive reactions. Herein, a fluorescence sensor 1,4-bis((E)-(2-(benzo[d]thiazol-2-yl)hydrazineylidene)methyl)benzene (DHB) was designed and synthesised by a simple one-step reaction using 2-hydrazinobenzothiazole and terephthalaldehyde as raw materials. DHB showed aggregation-induced emission characteristics in solid state and 1,4-dioxane/H2O mixture. In addition, the fluorescent colour changes in IPA and fluorescence quenching in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), dimethyl sulphoxide (DMSO), glycerine (GI), and 1,3-propanediol (1,3-PDO) were obviously observed with increasing water content, making DHB a highly sensitive fluorescent sensor for water detection with a detection limit of 0.174% for IPA, 0.040% for DMSO, 0.067% for DMF, 0.039% for DMA, 0.069% for 1,3-PDO, and 0.013% for GI, respectively. Further, DHB displayed fluorescence colorimetric response to water in solid state. 1H NMR titration indicated that the sensing mechanism for the detection of trace water was form hydrogen bonds between H2O molecule and amino group of DHB.

Inside Back Cover: Aggregation‐induced emission of copper nanoclusters

Copper nanoclusters have recently emerged as promising luminophores, and their AIE properties have promoted a plenty of potential applications. This review summarizes the recent research progress on design of ligands, and the ways on how to induce aggregation of the Cu nanoclusters. Special emphasis is put onthe current understanding of emission mechanisms of Cu nanoclusters experiencing AIE. (Aggregate. 2021;2:e112)

ACQ-to-AIE conversion by regio-isomerization of rofecoxib analogues for developing new multi-functional aggregation-induced emission luminogens

The development of aggregation induced emission luminogens (AIEgens) has attracted increasing attention in recent years as the potential of their application in various areas, including data storage and bioimaging has been realised. However, most of the AIEgens have large conjugation systems which were obtained via lengthy synthetic processes. Herein, we have successfully developed a new pair of far-red fluorescent molecules (λmax = 652 nm, 688 nm), ROF1 and ROF2, which were designed and derivatized from rofecoxib by one-step reaction. Specifically, ROF1 with a para-piperidine shows a classical aggregation caused quenching (ACQ) effect. In contrast, by shifting the piperidine group from para-to ortho-position, the ROF2 exhibits typical AIE behavior. Based on the analyses of single-crystal X-ray data, the AIE property of ROF2 could be ascribed to the highly twisted molecular conformation and loose packing modes caused by the ortho-position of piperidine. These findings allow us to have a better understanding of the impact of the substituent position on the AIE properties. Moreover, the fluorescence of ROF2 was sensitive to multi-stimulus, such as grinding, immersing (solvating), heating and altering pH value, which enabled its potential application in data storage, security ink and pH sensing. In biological experiments, ROF2 could selectively image lipid droplets (LDs) in living HeLa cells. In summary, the regio-isomerization effect used in this article successfully developed a promising AIEgen, ROF2, and provided a principle for the design of new AIEgens.

Ultrabright AIE of Ir(III) complexes achieving expeditious monitoring of oxygen and high-definition development of latent fingerprints

AIEgens have been widely applied in the fields involving solid and aggregation states. However, the preparation of AIEgens with high brightness to obtain the optimum AIE performance remains a challenge. In this article, a finely structural design strategy for the creation of ultrabright AIEgens has been reported based on Ir(III) complexes. By stepwise heightening the motion activity of substituents, the AIE property of Ir(III) complexes can be activated with dramatically improved photoluminescence quantum yields in solid state. The dipole moment vector of substituents and the triplet lifetime of Ir(III) complexes were applied to verify the motion activity of substituents theoretically and experimentally. In addition, by the combination of AIE-active Ir(III) complex IrppyDPBA and air permeable, optically transparent ethylcellulose, a hypersensitive luminescent oxygen sensing film with ultrafast quenching/recovery cycles in 6.1 s was developed. And the high-brightness AIE significantly improved the oxygen sensitivity of Ir(III) complexes. Furthermore, the expeditious and high-definition development of latent fingerprints on the substrates of tinfoil, plastic, steel, and glass was demonstrated by the high-brightness AIE of IrppyDPBA in 3 min. The fingerprint photographs developed by IrppyDPBA were intact and legible enough to allow display and analyze down to level 3 details. Noteworthily, the synergistic enhancement of the AIE property and the RTP nature of Ir(III) complexes on LFP development was for the first time demonstrated.

Polyurea Modified with 4‐Dihydropyrimidone‐2‐ketone Rings by Biginelli Reaction and its Boostered AIE Characteristic

AbstractIn the synthesis of traditional AIE‐active polymers with conjugate or multi‐benzene system, the troublesome process is still faced such as consuming time, high temperature, catalysis, no water or vacuum, and so on. In this study, the polydihydropyrimidone derivatives (PDPMDs) with AIE properties are facilely synthesized by the introduction of 4‐dihydropyrimidone rings onto non‐AIE‐active intermediate polyureas (PUs) in Biginelli reaction. It is found that the unsymmetrical L‐lysine ethyl diisocyanate and butylenediamine played a very important role in the smooth preparation and fluorescence enhancement of PDPMDs. Compared with the intermediate PUs, the fluorescence of PDPMDs is significantly enhanced (35‐fold increase), which is mainly due to the intramolecular aggregation of dihydropyrimidone rings on PUs chains. At the same time, with the increase of the content of dihydropyrimidone rings, the fluorescence intensity of PDPMDs also increases, and the emission wavelength shows an obvious red shift. The fluorescence of PDPMDs also showed obvious dependence on excitation wavelength, which further reveals the clusterization‐triggering emission (CTE) mechanism. In summary, the strategy of endowing AIE properties to non‐AIE active polymer by introducing heterocycles into the backbone through multi‐component reaction provides useful guidance for AIE functionalization of other non‐AIE materials.

A novel near-infrared viscosity probe based on synergistic effect of AIE property and molecular rotors for mitophagy imaging during liver injury

Mitophagy, a specialized form of autophagy, holds the key to cellular metabolism and physiology. Viscosity is a significant marker for visualization of the mitophagy process in real-time. Hence, development of well-performing viscosity probe is beneficial to study mitophagy-related dynamic physiological and pathological processes. Here, a new strategy was proposed by combination of AIE property and molecular rotors to design novel viscosity probe. The probe named TPA-Py was obtained by Knoevenagel condensation reaction of AIE unit and pyridine salt, which giving the probe excellent near-infrared emission, good water-solubility and mitochondrial targeting ability. Most importantly, TPA-Py owns two rotatable parts of triphenylamine and double bond, enabling the probe to equip with AIE property and sensitive recognition units for viscosity. With the environmental viscosity increasing, the rotation of the molecular rotor and the AIE unit is restricted effectively, the probe displayed strong fluorescence. Then, TPA-Py was successfully employed for monitoring the mitophagy process in A549 cells by imaging viscosity alterations. As mitophagy constitutes an important consideration in the pathogenesis of drug-induced liver injury, TPA-Py was also applied to explore the variation of viscosity in production and remediation pathways of APAP-induced liver injury. These results demonstrated that TPA-Py was a highly sensitive viscosity probe which holds great potential of biological applications.

Palladium-Catalyzed Three-Component Cascade Reaction of Nitriles: Synthesis of 2-Arylquinoline-4-carboxylates.

A new method for converting easy availability starting materials 2-(2-oxoindolin-3-yl)acetonitrile, arylboronic acids, and alcohols into 2-arylquinoline-4-carboxylates is reported. The procedure involves a three-component addition/ring expansion/esterification reaction in the presence of Pd(II) catalyst with high functional group tolerance under mild conditions. In addition, the photophysical properties of the resulting product were investigated and exhibited excellent polarity-sensitive fluorescence properties and AIE property.

Photo-Switchable Aggregation-Induced Emission of Bisthienylethene-Dipyrimido[2,1-b][1,3]benzothiazole Triad.

A bisthienylethene-dipyrimido[2,1-b][1,3]benzothiazole (BTE-2PBT) triad has been designed and synthesized based on our recent discovery of PBTs as atypical propeller-shaped novel AIEgens. The triad not only maintains the photochromic properties of BTE moiety in solution, film, and solid state but also exhibits remarkable AIE properties. Moreover, the fluorescence of BTE-2PBT PMMA film could be modulated with high contrast by alternate UV and visible light irradiation. Photoerasing, rewriting, and non-destructive readout of fluorescent images on BTE-2PBT PMMA film well demonstrate its potential application as optical memory media.

Molecular Structural Evolution of Near-Infrared Cationic Aggregation-Induced Emission Luminogens: Preclinical Antimicrobial Pathogens Activities and Tissues Regeneration

Molecular Structural Evolution of Near-Infrared Cationic Aggregation-Induced Emission Luminogens: Preclinical Antimicrobial Pathogens Activities and Tissues Regeneration

BOPHY-Based Aggregation-Induced-Emission Nanoparticle Photosensitizers for Photodynamic Therapy

Photosensitizers for photodynamic therapy (PDT) of cancer have been widely investigated over the past decades. However, the notorious aggregation-caused quenching (ACQ) effect limits their further biological applications. In this work, we have designed and reported a photosensitizer BOPHY-2TPA. The formed photosensitizer BOPHY-2TPA was a donor–acceptor–donor (D–A–D) structure with the BOPHY as an acceptor core and two triphenylamine (TPAs) as the electron donor units. The BOPHY-2TPA exhibited a large Stokes shift and excellent photoinduced 1O2 generation capabilities. Besides, the twisted structure of TPAs endowed the BOPHY-2TPA with intrinsic AIE properties, which effectively avoided the ACQ effect. Because of these prominent features, the BOPHY-2TPA aggregates encapsulated with biocompatible Pluronic P123 in aqueous solution showed high PDT antitumor efficiency.

Imidazole-based solid-state fluorophores with combined ESIPT and AIE features as self-absorption-free non-doped emitters for electroluminescent devices

Excited-state intramolecular proton transfer (ESIPT) fluorophores with an eye-catching aspect of a large Stokes shift in optical properties have been exceptionally considered as prime candidates for numerous applications. Nevertheless, as non-doped emitters for electroluminescent devices, the device performance is still far behind the traditional fluorescence emitters. Herein, two imidazole-based ESIPT-aggregate induced emission (AIE) fluorophores (HITPE and HPITPE) are designed and synthesized by covalently linked the ESIPT cores of 2-(2-hydroxyphenyl)-1,4,5-triphenylimidazole (HI) and 2-(2-hydroxylphenyl)-1-phenylphenanthroimidazole (HPI) with AIE-active luminogen of tetraphenylethene (TPE) at 5-position of the 2-hydroxyphenyl unit. The ESIPT, AIE, and photophysical properties are theoretically and experimentally studied. Both molecules display ESIPT and AIE characters with intense sky-blue/green-blue color emissions from a pure keto form in the solid-state and photoluminescence quantum yields of 57–64%. They possess high thermal and electrochemical stabilities. They are successfully fabricated as non-doped emitters in organic light-emitting diodes (OLED), and all devices exhibit strong keto-form emissions with low turn-on voltages (3.0–3.2 V). Especially, HPITPE-based OLED achieves a high luminance of 10680 cd m−2, LE value of 3.67 cd A−1, and external quantum efficiency (EQE) of 3.26% with a slight efficiency roll-off. Importantly, this represents an advance in the development of ESIPT molecules as a non-doped emitter for fluorescent OLEDs.

Making Aggregation-Induced Emission Luminogen More Valuable by Gold: Enhancing Anticancer Efficacy by Suppressing Thioredoxin Reductase Activity.

Gold complexes have been recognized as potential anticancer agents against various kinds of diseases due to their inherent suppressions of antioxidant thioredoxin reductase (TrxR) activity. Herein, a powerful aggregation-induced emission luminogen (AIEgen), TBP-Au, was designed and synthesized by integrating an anticancer Au(I) moiety with an AIE-active photosensitizer (TBP), in which both the production and consumption routes of reactive oxygen species (ROS) were elaborately considered simultaneously to boost the anticancer efficacy. It has been demonstrated that TBP-Au could realize superior two-photon fluorescence imaging in tumor tissues with high resolution and deep penetration as well as long-term imaging in live animals due to its AIE property. In addition, the introduction of a special Au(I) moiety could tune the organelle specificity and efficiently facilitate the ROS-determined photodynamic therapy (PDT). More impressively, TBP-Au could efficiently eliminate cancer cells under light irradiation through the preconceived synergetic approaches from the PDT and the effective suppression of TrxR, demonstrating that TBP-Au holds great potential for precise cancer theranostics.