Innovative Synthetic Procedures for Luminogens Showing Aggregation-Induced Emission

Palladium-Catalyzed Triple Suzuki-Miyaura Reactions Using Cyclic (Vinyl Triflate)iodonium Salts

By using cyclic (vinyl triflate)iodonium salts, a novel triple Suzuki-Miyaura reaction was accomplished for the synthesis of polyaromatic ethylene derivatives in the presence of palladium catalysts. The reaction exhibits extensive compatibility with a wide range of readily available arylboronic acids, giving triaryl-substituted ethylenes in good yields.

Progress of NIR-II fluorescence imaging technology applied to disease diagnosis and treatment

Near-infrared two-region (NIR-II, 1000-1700 nm) fluorescence imaging has received widespread attention because of its high in vivo penetration depth, high imaging resolution, fast imaging speed and high efficiency, dynamic imaging, and high clinical translatability. This paper reviews the application of NIR-II imaging technology in disease diagnosis and treatment. The paper highlights the latest research progress of commonly used NIR-II imaging materials and the latest progress of multifunctional diagnostic platforms based on NIR-II imaging technology, and discusses the challenges and directions for the development and utilization of novel NIR-II imaging probes.

N-Vinylthio Phthalimides (N-VTPs): Modular Reagents for Vinylthio AIEgen Transfer

Novel sulfur reagents N-vinylthio phthalimides (N-VTPs) have been employed as modular reagents for vinylthiolation, enabling the construction of aggregation-induced emission (AIE)-active tetraaryldivinyl sulfides (TADVSs) and diarylvinyl sulfides (DAVSs). Notably, TADVSs with sulfur insertion to ethene stators are reported as AIE luminogens (AIEgens) for the first time, and the corresponding photophysical properties and aggregated confirmation have been detailed for the demonstration of the AIE effect. A water-soluble TADVS with a quinolinium salt was prepared for cell imaging.

Thiophene π-bridge-based second near-infrared luminogens with aggregation-induced emission for biomedical applications

In the past 5 years, aggregation-induced emission luminogens (AIEgens) with emission in the second near-infrared (NIR-II) optical window have aroused great interest in bioimaging and disease phototheranostics, benefiting from the merits of deep penetration depth, reduced light scatting, high spatial resolution, and minimal photodamage. To construct NIR-II AIEgens, thiophene derivatives are frequently adopted as π-bridge by virtue of their electron-rich feature and good modifiability. Herein, we summarize the recent progress of NIR-II AIEgens by employing thiophene derivatives as π-bridge mainly compassing unsubstituted thiophene, alkyl thiophene, 3,4-ethylenedioxythiophene, and benzo[c]thiophene, with a discussion on their structure-property relationships and biomedical applications. Finally, a brief conclusion and perspective on this fascinating area are offered.

An AIE Metal Iridium Complex: Photophysical Properties and Singlet Oxygen Generation Capacity

Photodynamic therapy (PDT) has garnered significant attention in the fields of cancer treatment and drug-resistant bacteria eradication due to its non-invasive nature and spatiotemporal controllability. Iridium complexes have captivated researchers owing to their tunable structure, exceptional optical properties, and substantial Stokes displacement. However, most of these complexes suffer from aggregation-induced quenching, leading to diminished luminous efficiency. In contrast to conventional photosensitizers, photosensitizers exhibiting aggregation-induced luminescence (AIE) properties retain the ability to generate a large number of reactive oxygen species when aggregated. To overcome these limitations, we designed and synthesized a novel iridium complex named Ir-TPA in this study. It incorporates quinoline triphenylamine cyclomethylated ligands that confer AIE characteristics for Ir-TPA. We systematically investigated the photophysical properties, AIE behavior, spectral features, and reactive oxygen generation capacity of Ir-TPA. The results demonstrate that Ir-TPA exhibits excellent optical properties with pronounced AIE phenomenon and robust capability for producing singlet oxygen species. This work not only introduces a new class of metal iridium complex photosensitizer with AIE attributes but also holds promise for achieving remarkable photodynamic therapeutic effects in future cellular experiments and biological studies.

Enhancing NIR-II Imaging and Photothermal Therapy for Improved Oral Cancer Theranostics by Combining TICT and Aggregation-Induced Emission

In the treatment process of cancers like oral cancer, it is necessary to employ extensive surgical resection to achieve cancer eradication. However, this often results in damage to crucial functions such as chewing and speaking, leading to a poorer prognosis and a reduced quality of life. To address this issue, a multifunctional theranostic agent named MBPN-T-BTD has been developed by precisely modulating the excitation state energy distribution in the radiative/nonradiative decay pathways using the characteristics of twisted intramolecular charge transfer and aggregation-induced emission. This agent outperforms clinically utilized indocyanine green (ICG) in various aspects, including the second near-infrared window (NIR-II, 1000-1700 nm) fluorescence (FL) and photothermal conversion efficiency (PCE). Its nanoparticle form (BTB NPs) can be effectively used for high-contrast delineation of lymph node mapping and tongue and floor of mouth cancers using NIR-II FL, enabling surgeons to achieve more precise and thorough tumor clearance. For tumors located in close proximity to vital organs such as the tongue, the exceptional PCE (71.96%) of BTB NPs allows for targeted photothermal ablation with minimal damage to peripheral healthy tissues. This contribution provides a safer and more effective paradigm for minimally invasive or noninvasive treatment of oral cancer, ensuring the preservation of normal organ functions and showing potential for improving the overall prognosis and quality of life for cancer patients.

Aggregation‐enabled alkene insertion into carbon–halogen bonds

Molecular aggregation affects the electronic interactions between molecules and has emerged as a powerful tool in material science. Aggregate effect finds wide applications in the research of new physical phenomena; however, its value for chemical reaction development has been far less explored. Herein, we report the development of aggregation‐enabled alkene insertion into carbon–halogen bonds. The spontaneous cleavage of C–X (X = Cl, Br, or I) bonds generates an intimate ion pair, which can be quickly captured by alkenes in an aggregated state. Additional catalysts or promoters are not necessary under such circumstances, and solvent quenching experiments indicate that the aggregated state is critical for achieving such sequences. The ionic insertion mode is supported by mechanistic studies, density functional theory calculations, and symmetry‐adapted perturbation theory analysis. Results also show that the non‐aggregated state may quench the transition state and terminate the insertion process.

Overview of nanozymes with phosphatase-like activity

Nanomaterials with intrinsic enzyme activity, referred to as nanozymes, have attracted substantial attention in recent years. Among them, phosphatase-mimicking nanozymes have become an increasingly important focus for future research, considering that phosphatase is not only one of key enzymes for phosphorous metabolism, which is essential for many biological processes (e.g., cellular regulation and signaling), but also one of extensively used biocatalytic labels in the enzyme-linked assays as well as a powerful tool enzyme in molecular biology laboratories. Nevertheless, compared with extensive oxidoreductase-mimicking nanozymes, there are a very limited number of nanozymes with phosphatase-like activity have been explored at present. The increasing demand of complex and individualized phosphatase-involved catalytic behaviors is pushing the development of more advanced phosphatase-mimicking nanozymes. Thus, we present an overview on recently reported phosphatase-like nanozymes, providing guidelines and new insights for designing more advanced phosphatase-mimicking nanozyme with superior properties.

Recent advances of AIE-active materials for orthotopic tumor phototheranostics

Cancer ranks as a leading threat to human life and health. Compared to conventional cancer treatments, phototheranostics shares the advantages of integrated diagnosis and therapy, outstanding therapeutic performance and good controllability. Amid diverse phototheranostic agents, small organic luminogens with aggregation-induced emission (AIEgen) tendency show predominant advantages in terms of superior photostability, large Stokes shifts, and boosted theranostic capacity as aggregates. In the past two decades, AIE-active materials have demonstrated formidable applications in disease theranostics, especially for tumors. This review mainly highlights the recent advances of orthotopic tumor phototheranostics mediated by AIEgens with a classification of different organs. Additionally, a brief discussion of current bottlenecks and future directions is outlined. We believe this review can deepen the understanding and spur more innovations on tumor theranostics by employing AIEgens. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

I2-Promoted gem-Diarylethene Involved Aza-Diels-Alder Reaction and Wagner-Meerwein Rearrangement: Construction of 2,3,4-Trisubstituted Pyrimido[1,2-b]indazole Skeletons

A [3 + 1 + 2] cyclization-rearrangement reaction scheme was developed to synthesize pyrimido[1,2-b]indazoles from aryl methyl ketones, 3-aminoindazoles, and gem-diarylethenes. This metal-free process proceeds via a sequential aza-Diels-Alder reaction and Wagner-Meerwein rearrangement, and a possible reaction mechanism was demonstrated based on control experiments. This method exhibits good substrate compatibility and allows simple reaction conditions. Moreover, the products display significant aggregation-induced emission characteristics after simple modifications.

Multifunctional AIE Nanosphere-Based "Nanobomb" for Trimodal Imaging-Guided Photothermal/Photodynamic/Pharmacological Therapy of Drug-Resistant Bacterial Infections

Injudicious or inappropriate use of antibiotics has led to the prevalence of drug-resistant bacteria, posing a huge menace to global health. Here, a self-assembled aggregation-induced emission (AIE) nanosphere (AIE-PEG₁₀₀₀ NPs) that simultaneously possesses near-infrared region II (NIR-II) fluorescence emissive, photothermal, and photodynamic properties is prepared using a multifunctional AIE luminogen (AIE-4COOH). The AIE-PEG₁₀₀₀ NPs were encapsulated with teicoplanin (Tei) and ammonium bicarbonate (AB) into lipid nanovesicles to form a laser-activated "nanobomb" (AIE-Tei@AB NVs) for the multimodal theranostics of drug-resistant bacterial infections. In vivo experiments validate that the "nanobomb" enables high-performance NIR-II fluorescence, infrared thermal, and ultrasound (AB decomposition during the photothermal process to produce numerous CO₂/NH₃ bubbles, which is an efficient ultrasound contrast agent) imaging of multidrug-resistant bacteria-infected foci after intravenous administration of AIE-Tei@AB NVs followed by 660 nm laser stimulation. The highly efficient photothermal and photodynamic features of AIE-Tei@AB NVs, combined with the excellent pharmacological property of rapidly released Tei during bubble generation and NV disintegration, collectively promote broad-spectrum eradication of three clinically isolated multidrug-resistant bacteria strains and rapid healing of infected wounds. This multimodal imaging-guided synergistic therapeutic strategy can be extended for the theranostics of superbugs.

A rational design of polymers through donor modulation to weaken the aggregation-caused quenching effect for NIR-II fluorescence imaging

The great tissue penetration depth and low tissue autofluorescence of NIR-II fluorescence imaging make it attractive for in vivo diagnosis. However, the aggregation-caused quenching (ACQ) effect is among the dominant obstacles that weaken NIR-II imaging and restrict its application. Herein, the donor unit, 2,8-dibromo-6H,12H-5,11-methanodibenzo[b,f] [1,5]diazocine with a V-configuration, was introduced to prepare the donor-acceptor (D-A) polymer P-TB with a twisted backbone, while the planar D-A polymer P-TP was used as a control. P-TB and P-TP were prepared by Stille Coupling with DPP as the acceptor. The main absorption peaks of P-TB and P-TP are located at 610 nm and 640 nm, and the emission peaks of P-TB and P-TP are 1060 nm and 930 nm, respectively. Significantly, the V-shaped P-TB showed no obvious ACQ effect within 600 μM, and the same phenomenon was demonstrated during in vivo NIR-II imaging in mice, which proves that the introduction of V-configuration donor units is beneficial for weakening the ACQ effect. This work outlines a prospective tactic for the design of conventional NIR-II fluorescent polymers by modulating the configuration of the donor units.

Luminescent MOFs constructed by using butterfly-like AIE ligands

In this work, a series of butterfly-like isomers named oxacalix[2]naphthalene[2]pyrazine (ONP) were conveniently synthesized by a one-step catalyst-free reaction in a facile manner, and they exhibit typical characteristics of aggregation-induced emission (AIE). The mechanism study shows that restriction of intramolecular vibration (RIV) is the reason for their AIE properties. The pyrazine groups endow ONP molecules with good coordination ability, which makes them ideal ligands for constructing metal-organic frameworks (MOFs). Thus, three ONP-based luminescent MOFs were constructed, and they exhibit intense emission with lifetimes in the order of microseconds. More importantly, different ONP isomers have different binding capacities, and thus only one kind of MOF can be obtained even when using an isomer mixture of ONP ligands. This result suggested that the conformation of ONPs is an important determining factor for their application as bridging ligands. This work not only reports a series of new RIV-type AIEgens, but also offers a new platform for the construction of luminescent MOFs.

9,9-Bis[4-(N-aryl)phenyl]methylidene-xanthylidene Derivatives Displaying Mechano-, Crystallo-, and Thermochromism

Tetraphenylethylene (TPE) derivatives bearing a xanthene moiety are of interest because they have novel optical properties. 9,9-Bis[4-(N,N-diphenylamino)phenyl] and 9,9-bis[4-(9-carbazolyl)-phenyl]methylidene-xanthylidenes 3 and 4 were synthesized using Suzuki-Miyaura coupling of 9,9-dibromomethylidene-xanthylidene with the corresponding boronic acids. Diphenylamino derivative 3 exhibits mechanochromism and mechanofluorochromism (MC and MFC) reflected in absorption and fluorescence color changes. In contrast, carbazolyl derivative 4 displays thermo- and crystallo-chromism in addition to MC and MFC in the solid state. Powder X-ray diffraction and single crystal X-ray crystallographic analysis reveal that the solid state photophysical properties of these substances are governed by conformational changes rather by the creation of planar π-conjugation extended geometries.

High-contrast reversible multiple color-tunable solid luminescent ionic polymers for dynamic multilevel anti-counterfeiting

Dynamic color-tunable luminescent materials, which possess huge potential applications in advanced multilevel luminescence anti-counterfeiting, are of considerable interest. However, it remains challenging to develop simple high-contrast reversible multiple (triple or more than triple) color-tunable high-efficiency solid luminescent materials with low cost, facile synthesis, and good processability. Herein, by simply grafting charged multi-color AIEgen-based chromophores into polymers, a series of high-efficiency multiple color-tunable luminescent single ionic polymers are constructed through tuning feed ratios, counter anions and reaction solvents. Remarkably, some ionic polymers can not only achieve rare high-contrast reversible multiple color-tunable emission in solid states in response to different solvent stimuli, but also could realize excitation-dependent color-tunable emission. To the best of our knowledge, such charming multiple (triple or more than triple) color-tunable solid polymers responding to multiple external stimuli are still rare. Based on comparative studies of emission spectra, excitation spectra and fluorescence lifetimes before and after swelling, it could be inferred that solvent stimuli could induce microstructure changes of these ionic polymers and then change the aggregated-states of their corresponding AIE-active emission centers. Moreover, the different solvent stimuli could induce to produce different degrees of microstructure changes, resulting in their unique multiple color-tunable emission. More significantly, these smart color-tunable ionic polymers show great promise for applications in dynamic multilevel (three-level or even more than three-level) anti-counterfeiting.

Four-Winged Propeller-Shaped Indole-Modified and Indole-Substituted Tetraphenylethylenes: Greenish-Blue Emitters with Aggregation-Induced Emission Features for Conventional Organic Light-Emitting Diodes

Aggregation-induced emission (AIE) is an extraordinary photochemical phenomenon described by Tang's group in 2001, where the aggregation of some organic molecules enhances their light emission by limiting intramolecular activity in the aggregate state. This phenomenon offers new opportunities for researchers due to its potential applications in optoelectronics, energy, and biophysics. Tetraphenylethylenes (TPEs) are reliable AIE luminogens with a wide range of successful applications in material chemistry. To expand the library of AIE-active TPEs, both a series of TPE analogues, in which the phenyl rotor has been replaced by the indole ring, and indole-substituted TPE derivatives were designed and synthesized through vinyl-aryl and aryl-aryl bond formations using the Suzuki coupling reaction. Efficient synthetic routes that delivered indole-modified and indole-substituted TPEs have been developed, and almost all heterocyclic TPE analogues have demonstrated AIE behavior. Furthermore, to test whether the indole ring can be diversified, two title compounds were converted to a series of bis(indolyl)methane (BIM), and these BIM-TPE materials showed typical AIE properties. Interestingly, two compounds indicated a solvent vapor fuming reversible switch between bright blue emission and greenish-yellow emission. Upon fuming with dichloromethane, their fluorescence spectra showed 8 and 32 nm red-shift and could return to the original state after fuming with hexane. Furthermore, we have explored the effects of replacing the phenyl ring in TPE with indole together with the substitution of TPE with indole ring(s) on the performance of organic light-emitting diode (OLED) device applications. In addition, density functional theory calculations; the optical, electrochemical, light emission, electroluminescence characteristics; and admittance spectroscopic analysis of OLED devices of four representative TPEs have been investigated in detail. As a result, the indole-TPEs are potential blue emitters with AIE features for conventional OLEDs, which is a significant color in displays and lighting.

TfR Aptamer Enhanced Blood-Brain Barrier Penetration of Biomimetic Nanocomplexes for Intracellular Transglutaminase 2 Imaging and Silencing in Glioma

Engineering a versatile nanocomplex integrating effective penetration of the blood-brain barrier (BBB), accurate diagnosis, and boosting therapy has always been an intractable challenge in glioblastoma multiforme (GBM). Herein, biomimetic nanocomplexes (TMPsM) for single intracellular transglutaminase 2 (TG2)-triggered self-assembly imaging and RNAi therapy for GBM are subtly developed. To prove the concept, transferrin receptor (TfR) aptamer-modified brain metastatic tumor cell membrane is prepared as the shell for dual BBB targeting capability and prolonged blood retention time. Upon targeting entering into GBM, hollow MnO₂ is decomposed to release KKGKGQQ-tetraphenylethene (Pep-TPE) and siRNA. Owing to TG2 dependence, the non-emissive Pep-TPE would be self-aggregated to induce the emission turn-on in GBM that contain overexpressed TG2. The resulting aggregation-induced emission fluorescence imaging with a high signal-to-noise ratio can achieve the precise localization of the tumor and dynamic detection of TG2 activity, thereby allowing the GBM accurate diagnosis. Notably, the TG2 can be silenced by the released siRNA to cause cell apoptosis and increase chemotherapeutic sensitivity, ultimately realizing excellent antitumor efficacy. In vitro and in vivo results demonstrate that the as-prepared TMPsM indeed possess superior BBB penetration, precise diagnosis, and effective therapy of GBM. The proposed strategy may pioneer a new path for the theranostics of brain tumors.

A switchable redox annulation of 2-nitroarylethanols affording N-heterocycles: photoexcited nitro as a multifunctional handle

The efficient transformation of nitroaromatics to functional molecules such as N-heterocycles has been an attractive and significant topic in synthesis chemistry. Herein, a photoexcited nitro-induced strategy for switchable annulations of 2-nitroarylethanols was developed to construct N-heterocycles including indoles, N-hydroxyl oxindoles and N-H oxindoles. The metal- and photocatalyst-free reaction proceeds through intramolecular redox C-N coupling of branched hydroxyalkyl and nitro units, which is initiated by a double hydrogen atom abstraction (d-HAA) process. The key to the switchable reaction outcomes is the mediation of a diboron reagent by its favorable oxy-transfer reactivity to in situ generated nitroso species. The utility of this protocol was well demonstrated by broad substrate scope, excellent yields, functional group tolerance and wide applications. Finally, detailed mechanistic studies were performed, and kinetic isotope effect (KIE) experiments indicate that the homolysis of the C-H bond is involved in the rate-determining step.

Fibrous aggregates: Amplifying aggregation-induced emission to boost health protection

Environmental monitoring and personal protection are critical for preventing and for protecting human health during all infectious disease outbreaks (including COVID-19). Fluorescent probes combining sensing, imaging and therapy functions, could not only afford direct visualizing existence of biotargets and monitoring their dynamic information, but also provide therapeutic functions for killing various bacteria or viruses. Luminogens with aggregation-induced emission (AIE) could be well suited for above requirements because of their typical photophysical properties and therapeutic functions. Integration of these molecules with fibers or textiles is of great interest for developing flexible devices and wearable systems. In this review, we mainly focus on how fibers and AIEgens to be combined for health protection based on the latest advances in biosensing and bioprotection. We first discuss the construction of fibrous sensors for visualization of biomolecules. Next recent advances in therapeutic fabrics for individual protection are introduced. Finally, the current challenges and future opportunities for "AIE + Fiber" in sensing and therapeutic applications are presented.

"One Stone, Four Birds" Ion Engineering to Fabricate Versatile Core-Shell Organosilica Nanoparticles for Intelligent Nanotheranostics

Developing effective intelligent nanotheranostics is highly desirable for cancer treatment but remains challenging. In this study, an acidic tumor microenvironment-activated organosilica nanosystem, namely AD-Cu-DOX-HA, is straightforwardly constructed, which is composed of aggregation-induced emission (AIE)-active photosensitizer, copper ion-engineered aminosilica, direct coordination polymer of doxorubicin (DOX), and targeting component hyaluronic acid (HA). AD-Cu-DOX-HA is able to accurately distinguish cancer cells over normal cells; meanwhile, it simultaneously exhibits selective accumulation and copper ion-mediated rapid disassembly and turn-on fluorescence in tumor tissue, consequently achieving efficient tumor diagnosis and tumor-growth inhibition through fluorescence imaging-navigated synergetic photodynamic therapy, copper ion-mediated chemodynamic therapy, and DOX-enabled chemotherapy. This work thus brings fresh insight into the exploration of versatile theranostics and presents a momentous advance for potential clinical cancer treatment.

Three-Color White Photoluminescence Emission Using Perovskite Nanoplatelets and Organic Emitter

Three organic blue-light-emitting tetraphenylethylene (TPE) derivatives that exhibit aggregation-induced emission (AIE) were used as additives in the preparation of inorganic perovskite-structured green-light-emitting materials for three-color white-light emission. For these organic–inorganic light-emitting materials, two-color (blue and green) light-emitting films based on the CsPbBr₃ perovskite-structured green-light-emitting inorganic material were prepared. The three TPE derivatives were prepared by varying the number of bromide groups, and a distinct AIE effect was confirmed when the derivatives were dissolved in a water–tetrahydrofuran mixed solvent containing 90 vol% water. When 0.2 molar ratio of the 1,1,2,2-tetrakis(4-bromophenyl)ethylene (TeBrTPE) additive was mixed with nanocrystal-pinning toluene solvent, the green-light-emission photoluminescence quantum efficiency (PLQY) value at 535 nm was 47 times greater than that of the pure bulk CsPbBr₃ without additives and a blue emission at 475 nm was observed from the TeBrTPE itself. When a CBP:Ir(piq)₃ film was prepared on top of this layer, three PL peaks with maximum wavelength values of 470, 535, and 613 nm were confirmed. The film exhibited white-light emission with CIE color coordinates of (0.25, 0.36).

Multimodal Imaging-Guided Photothermal Immunotherapy Based on a Versatile NIR-II Aggregation-Induced Emission Luminogen

Synergistic photothermal immunotherapy has captured great attention owing to the mutually strengthening therapeutic outcomes towards both original tumors and abscopal tumors. Herein, a versatile theranostic agent displaying aggregation-induced emission, namely TPA-BT-DPTQ, was designed and prepared based on benzo[c]thiophene unit as a building block; it can be used for simultaneous fluorescence imaging (FLI) in the second near-infrared (NIR-II) window, photoacoustic imaging (PAI), photothermal imaging (PTI), and thermal eradication of tumors. Further experiments validate that photothermal therapy (PTT) mediated by TPA-BT-DPTQ nanoparticles not only destroys the primary tumor but also enhances immunogenicity for further suppressing the growth of tumors at distant sites. Furthermore, PTT combining a programmed death-ligand 1 (PD-L1) antibody prevents the metastasis and recurrence of cancer by potentiating the effect of immunotherapy.

Aggregation caused quenching to aggregation induced emission transformation: a precise tuning based on BN-doped polycyclic aromatic hydrocarbons toward subcellular organelle specific imaging

Polycyclic aromatic hydrocarbons (PAHs) with boron–nitrogen (BN) moieties have attracted tremendous interest due to their intriguing electronic and optoelectronic properties. However, most of the BN-fused π-systems reported to date are difficult to modify and exhibit traditional aggregation-caused quenching (ACQ) characteristics. This phenomenon greatly limits their scope of application. Thus, continuing efforts to seek novel, structurally distinct and functionally diverse structures are highly desirable. Herein, we proposed a one-stone-two-birds strategy including simultaneous exploration of reactivity and tuning of the optical and electronic properties for BN-containing π-skeletons through flexible regioselective functionalization engineering. In this way, three novel functionalized BN luminogens (DPA-BN-BFT, MeO-DPA-BN-BFT and DMA-DPA-BN-BFT) with similar structures were obtained. Intriguingly, DPA-BN-BFT, MeO-DPA-BN-BFT and DMA-DPA-BN-BFT exhibit completely different emission behaviors. Fluorogens DPA-BN-BFT and MeO-DPA-BN-BFT exhibit a typical ACQ effect; in sharp contrast, DMA-DPA-BN-BFT possesses a prominent aggregation induced emission (AIE) effect. To the best of our knowledge, this is the first report to integrate ACQ and AIE properties into one BN aromatic backbone with subtle modified structures. Comprehensive analysis of the crystal structure and theoretical calculations reveal that relatively large twisting angles, multiple intermolecular interactions and tight crystal packing modes endow DMA-DPA-BN-BFT with strong AIE behavior. More importantly, cell imaging demonstrated that luminescent materials DPA-BN-BFT and DMA-DPA-BN-BFT can highly selectively and sensitively detect lipid droplets (LDs) in living MCF-7 cells. Overall, this work provides a new viewpoint of the rational design and synthesis of advanced BN–polycyclic aromatics with AIE features and triggers the discovery of new functions and properties of azaborine chemistry.

A one-stone-two-birds strategy including simultaneous exploration of reactivity and tuning of the optical and electronic properties for BN-fused polycyclic aromatics through flexible regioselective functionalization engineering is presented.

Synthesis and application of near-infrared dyes based on sulfur-substituted dicyanomethylene-4H-chromene and diarylethene

Four novel compounds (S-DCM-1O, S-DCM-2O, S-DCM-3O, and S-DCM-4O) based on sulfur-substituted dicyanomethylene-4H-chromene (S-DCM) and diarylethene were synthesized. The detailed investigations on the fluorescence spectra, absorption spectra, time-dependent density functional theory...

Donor/π-Bridge Manipulation for Constructing a Stable NIR-II Aggregation-Induced Emission Luminogen with Balanced Phototheranostic Performance*

Owing to their versatile functionality and tunable energy dissipation, aggregation-induced emission luminogens (AIEgens) have emerged as a potential platform for multimodal theranostics. Nevertheless, the construction of AIE-active phototheranostic agents in the second near-infrared window (NIR-II, 1000-1700 nm), which allows superior resolution and minimized photodamage, is still a formidable challenge. Herein, benzo[c]thiophene serves as an electron-rich and bulky donor (D)/π-bridge, which can enlarge the conjugation length and distort the backbone of an AIEgen. By precise D/π-bridge engineering, highly stable NIR-II AIEgen DPBTA-DPTQ nanoparticles are obtained with acceptable NIR-II fluorescence quantum yield and excellent photothermal conversion efficiency. In addition, the spatial conformation of DPBTA-DPTQ is determined for the first time by X-ray single crystal diffraction and theoretical simulations. DPBTA-DPTQ NPs have good biocompatibility and show efficient photothermal therapeutic effects in in vitro tests. Furthermore, DPBTA-DPTQ NPs were used in fluorescence-photoacoustic-photothermal trimodal imaging-guided photothermal eradication of tumors in HepG2 and B16-F10 tumor-xenografted mice.

4-Azidocinnoline-Cinnoline-4-amine Pair as a New Fluorogenic and Fluorochromic Environment-Sensitive Probe

A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for the amine was detected in polar solvents with the strongest fluorescence increase in water. The environment-sensitive fluorogenic properties of cinnoline-4-amine in water were explained as a combination of two types of fluorescence mechanisms: aggregation-induced emission (AIE) and excited state intermolecular proton transfer (ESPT). The suitability of an azide-amine pair as a fluorogenic probe was tested using a HepG2 hepatic cancer cell line with detection by fluorescent microscopy, flow cytometry, and HPLC analysis of cells lysates. The results obtained confirm the possibility of the transformation of the azide to amine in cells and the potential applicability of the discovered fluorogenic and fluorochromic probe for different analytical and biological applications in aqueous medium.

Pyrene-Based Nonwoven Fabric with Tunable Fluorescence Properties by Employing the Aggregation-Caused Quenching Effect

Conventional aromatic compounds tend to exhibit the formation of sandwich-shaped excimers and exciplexes between their excited and ground states at high concentrations or in their aggregated states, causing their fluorescence to weaken or disappear due to the aggregation-caused quenching (ACQ) effect. This limits their applications in concentrated solutions or solid materials. Herein, for the first time, ACQ-based pyrene (Py) units are covalently connected to the surface of polyethylene/polypropylene nonwoven fabric (PE/PP NWF) via electron beam preradiation-induced graft polymerization followed by chemical modification. The matrix can be considered a solid solvent and Py units as a solid solute, such that the amount of Py units can be controlled by varying the reaction time. The obtained fluorescent fabric not only exhibits remarkable fluorescence properties with high fluorescence intensity, high quantum yield (>90%), and excellent fluorescence stability after laundering or in harsh chemical environments, but the fluorescence color and intensity, quantum yield, and lifetime can also be regulated by employing the ACQ effect. Additionally, the as-prepared fluorescent fabric can effectively distinguish common monocyclic aromatic hydrocarbons via a simple fluorescence response test.

Luminescent silver(i) complexes with pyrazole-tetraphenylethene ligands: turn-on fluorescence due to the coordination-driven rigidification and solvent-oriented structural transformation

A new tetrapyrazole-modified tetraphenylethene (TPE) ligand L was designed and found to display "turn-on" fluorescence when it combines with Ag⁺ ions in dilute solution by restricting intramolecular rotation of TPE. A series of Ag complexes 1-7 were obtained, and they exhibit excellent fluorescence properties in the solid state. Compared with PF₆^-, the silver complex with the CF₃SO₃^- anion can further enhance its fluorescence due to the transformation of its structure from Ag₂L (2) to Ag₄L₂ (3). As zero-dimensional complexes, 1 and 3 have excellent piezochromic properties with a color change from blue to green. Furthermore, structural changes of 1 and 3 to the corresponding three-dimensional frameworks 4 and 5 occur upon immersing in ethanol. In addition, 1 can act as a potential fluorescent probe for sensing nitrile compounds.

3,6-Diamino-7,8-dihydroisoquinoline-4-carbonitrile derivatives: unexpected facile synthesis, full-color-tunable solid-state emissions and mechanofluorochromic activities

A facile synthesis of novel 3,6-diamino-7,8-dihydroisoquinoline-4-carbonitrile derivatives and their solid-state emissions are presented.

Radiation-Induced In Situ-Printed Nonconjugated Fluorescent Nonwoven Fabric with Superior Fluorescent Properties

A new technique is proposed for the in situ printing of fluorescent fabrics with superior fluorescent properties that have the potential for continuous roll-to-roll production in the industry. Nonconjugated chemical moieties were covalently connected to polyethylene/polypropylene nonwoven fabric (PE/PP NWF) to successfully prepare fluorescent PE/PP NWF, which emits a bright blue light and has a high quantum yield (∼83.35%) that can be attributed to a unique aggregation-induced emission effect. The fluorescent PE/PP NWF exhibits excellent fluorescent stability under high shear forces during accelerated laundering and in harsh chemical environments. The fluorescent PE/PP NWF can also be tailored into diverse shapes and printed in situ with high resolution. The versatility of the method was also demonstrated by fabricating fluorescent materials with different polymer matrices such as Nylon 66 fiber and PE terephthalate membrane.