Topology modulation of tetraphenylethylene graphdiyne at a liquid-liquid interface

Monomers with low symmetries can form different topological structures in the preparation of organic two-dimensional(2D)materials.However,it remains challenging to modulate the topologies in practical synthesis.Leveraging theoretical insights into the formation energy of potential structural configurations,we report the topology modulation of a graphdiyne(GDY)derivative constructed from two-fold symmetric tetrakis(4-ethynylphenyl)ethene precursor by changing solvent combinations in a liquid-liquid interfacial system.An aqueous-organic(water-dichloromethane)interface afforded GDY with a kagome topology while a rhombic topology was formed at an organic-organic(hexane-acetonitrile)interface.A comprehensive evaluation of their structures and optoelectronic properties was conducted through various characterization techniques and theoretical computations.Our study provided new insights to modulate the topology of not only GDY but also other framework structures and obtain topologically pure materials in situations where different topologies are possible during practical synthesis.

Insight into the structural transformation of tetraphenylethylene acids at liquid–solid interface induced by linear aminofunctionalized triazine derivatives and annealing treatment

The interaction between organic photoelectric molecules leads to the formation of a certain aggregation structure,which plays a pivotal role in the charge transport at the intermolecular interface.In view of this,we investigated the mechanism and law of intermolecular interaction by detecting the self-assembled behaviors between organic photoelectric molecules at the interface by scanning tunneling microscopy(STM).In this work,the structural transformations of tetraphenylethylene acids(H_(4)ETTCs)on graphite surface induced by temperature and triazine derivatives(zcy-19,zcy-27,and zcy-38 molecules)were studied by STM technology and density functional theory(DFT)calculations.At room temperature,zcy-19 and H_(4)ETTC molecules formed a small range of ordered co-assembled nanostructure,while for zcy-27 or zcy-38 molecules,no co-assembled nanostructures were observed and only their own self-assembled structures existed on graphite surface,individually.In the thermal annealing trials,the original co-assembled H_(4)ETTC/zcy-19 structure disappeared,and only zcy-19 and H_(4)ETTC self-assembled in separate domains.Nevertheless,new well-ordered H_(4)ETTC/zcy-27 or H_(4)ETTC/zcy-38 co-assembled structures appeared at different annealing temperatures,respectively.Combined with DFT calculations,we further analyzed the mechanism of such structural transformations by triazine derivatives and temperature.Results reveal that triazine derivatives could interact with H_(4)ETTC by N–H···O and O–H···N hydrogen bondings,and whether temperature or zcy series compounds could achieve successful regulation of H_(4)ETTC assembly behavior is closely associated with the conjugated skeleton length of zcy series compounds.

AIE-active Metal-organic Coordination Complexes Based on Tetraphenylethylene Unit and Their Applications

Tetraphenylethylene(TPE) and its derivatives, as the widely used aggregation-induced emission(AIE) fluorophores, have attracted rapidly growing interest in the fields of material science and biological technology due to their unique light-emitting mechanism—they are nearly non-emissive in dilute solution but emit brilliant fluorescence in the aggregate state because of the restriction of intramolecular motion. Coordination-driven self-assembly, which provides a highly effective method to put the individual chromophores together, is consistent with the AIE mechanism of TPE. During the past few years, some AIE-active metal-organic coordination complexes have been successfully constructed via coordination-driven self-assembly, and their AIE properties and applications have been investigated. In this review, we survey the recent progress on TPE-based metal-organic coordination complexes and their applications in fluorescence sensors, cell imaging, and light-emitting materials. We will introduce them from three different types of structures: metallacycles, metallacages, and metal-organic frameworks(MOFs).

Fluorescence detection of perfluorooctane sulfonate in water employing a tetraphenylethylene-derived dual macrocycle Bowtie Cyclophane

Because the widely used perfluorooctane sulfonate(PFOS) is harmful to both environment and human health, it is of great significance and urgency to develop sensitive and selective sensors for the detection of trace PFOS in water. In this study, a tetraphenylethylene-derived macrocycle Bowtie Cyclophane has been developed as a fluorescent sensor based on aggregation-induced emission enhancement and fluorochromism. Sensitive detection of PFOS has been achieved with a limit of detection(LOD) of47.3 ± 2.0 nmol/L(25.4 ± 1.1 μg/L) accompanied by visual fluorescence color changes.

Synthesis and Detection of Pesticides of Luminescent Metal-organic Framework Based on Carboxyl-decorating Tetraphenylethylene

A water-stable porous anionic metal-organic framework(MOF),[(CH3)2NH2][In(TCPP)4/3]n·(2DMF)n(3H2O)n(1,TCPP=1,1,2,2-tetra(4-carboxylbiphenyl)ethylene),was synthesized.Here,compound 1 showed extremely high sensitivity and selectivity to current general-purpose pesticide 2,6-dichloro-4-nitroaniline(DCN)in aqueous solution.The fluorescence intensity of compound 1 could be decreased as much as 80%by 6 mL DCN,and it was almost completely quenched only with 20 mL DCN.The results indicate that compound 1 can act as a fluorescent probe for DCN.

Tetraphenylethylene-Based Emissive Supramolecular Metallacages Assembled by Terpyridine Ligands

We report the preparation and emission properties of tetraphenylethylene(TPE)-based metallacages with aggregation-induced emission(AIE)activities through coordination-driven self-assembly.Two supramolecular cages,[Zn6LA3]and[Zn6LB3],were assembled via TPE-decorated terpyridine(tpy)ligands,LA and LB,respectively,with Zn(II)ions.We performed a subtle change by introducing extra alkyne connectivity into LB to increase the degree of conjugation and geometric constraint,compared with LA.As a result,we obtained a highly emissive cage,[Zn6LB3],even in a dilute solution.

A polysaccharide/tetraphenylethylene-mediated blue-light emissive and injectable supramolecular hydrogel

A luminescent and injectable supramolecular hydrogel was successfully constructed through the non- covalent cross-linking of polymers mediated by tetraphenylethylene-bridged cyclodextrin oligomers, presenting the strong blue fluorescence, the reversible gelation behavior responsive to various external stimuli and the good mechanical property of shear thinning.

Circularly polarized luminescence based on cholesterol-tetraphenylethylene-perylene liquid crystal

Perylene derivative with circularly polarized luminescence(CPL) at aggregated state was seldom reported due to the strong ACQ(aggregation-caused quench) effect at aggregation. In this work, a novel cholesterol-tetraphenylethylene-perylene derivative(TPE-P) was designed and synthesized in moderate yield. It exhibited liquid crystalline behavior with orderly hexagonal columnar mesophase and good fluorescence emission at long wavelength(600-700 nm) not only in solution but also at aggregated states based on the AIE(aggregation-induced emission)-FRET(fluorescence resonance energy transfer) effect between tetraphenylethylene unit and perylene moiety. Moreover, the circular dichroism(CD) and CPL studies suggested the effective chiral transfer from cholesterol unit to tetraphenylethylene unit and perylene skeleton due to the spiral liquid crystalline self-assembly. The CD and CPL signals showed the order of THF < THF-hexane < solid film < meosphase, indicating that the higher spiral orderly degree resulted in the stronger chiral transfer. The largest |glum| value for mesophase excited at 320 nm was as high as 1.5×10^(−2) based on the combining effect of AIE-FRET and chiral transfer. This research not only reported a novel CPL perylene derivative at aggregated state, but also confirmed that the combination of AIE-FRET effect and chiral transfer of liquid crytalline phase was an effective method to construct normal dye with excellent CPL property in aggregated state.

Fabrication of Pyrene and Tetraphenylethylene Nanostructures by a Hydrolysis-Assisted Co-Assembly

The poly(allylamine hydrochloride)-g-pyrene-tetraphenylethylene(PAH-g-Py-g-TPE)copolymers with different ratios of Py and TPE are synthesized by grafting 1-pyrenecarboxaldehyde(Py-CHO)and tetraphenylethylene-carboxaldehyde(TPE-CHO)to PAH via a Schiff base reaction in methanol.The PAH-g-Py-g-TPE forms spherical micelles in water regardless of the ratios of Py and TPE,which can transform into different nanostructures after being incubated in pH 0 and pH 2 solutions,respectively.These nanomaterials including nanoparticles(NPs),nano-rods(NRs),nanotubes(NTs)and nanoribbons(NBs)are composed of Py-CHO and TPE-CHO with different ratios,and emit fluorescence with colors different from the pure Py NRs and NTs,and TPE NPs.

Photoinduced E to Z isomerization of tetraphenylethylene derivatives within organometallic supramolecular assemblies

Isolation of E-1,2-bis(4-bromophenyl)-1,2-diphenyl-ethylene from the E/Z isomer mixture obtained by a Mc Murry coupling reaction and reaction of this isomer with imidazole followed by N-alkylation with n Bu Br and anion exchange yielded the bisimidazolium tetraphenylethylene(TPE)derivative H_(2)-E-1(PF_(6))_(2).The reaction of H_(2)-E-1(PF_(6))_(2) with Ag_(2)O yielded the dinuclear metallarectangle[Ag_(2)(E-1)2](PF_(6))_(2) where the two bis-NHC donors E-1 bridge two silver atoms.Irradiation of[Ag_(2)(E-1)2](PF_(6))_(2) leads to E/Z isomerization of the di-NHC ligand and formation of Z-1 in the mononuclear complex[Ag(Z-1)]PF_(6).Demetallation of the di-NHC ligand with NH_(4)Cl/NH_(4)PF_(6) yielded bisimidazolium salt H_(2)-Z-1(PF_(6))_(2).The unique isomerization of the E-TPE derivative into its Z-isomer via metal complex formation/irradiation/demetallation cannot be achieved by irradiation of the individual imidazolium salt.The emissive properties of the TPE complexes[Ag_(2)(E-1)2](PF_(6))_(2) and[Ag(Z-1)]PF_(6) have been investigated.

A cationic amphiphilic tetraphenylethylene derivative with hydrochromic sensitive property:Applications in anti-counterfeiting ink and rewritable paper

Since the discovery of aggregation induced emission(AIE)phenomenon,various stimuli-responsive materials have been rapidly developed,but there are still great challenges in the application of ink printing due to the bad water solubility.In this research,a new cationic amphiphilic TPE-functionalized pyridine salt(TPE-OTs)was designed,which shows good water solubility and hydrochromic properties.The optical properties of the compound have been studied,which is equipped with the typical AIEE characteristics and TICT effect.The compound can self-assemble to form aggregates with a particle size of about 30 nm in water.What is more,the compound is responsive to the environmental humidity,whose fluorescent color changes from green to yellow as the humidity gradually increased.Based on this characteristic,we applied it to the fluorescent anti-counterfeiting ink,realizing the protection and encryption of information.

Hydrophobic Interface Cages in Microemulsions:Concept and Experiment Using Tetraphenylethylene-based Double-tailed Surfactant

Although hydrophobic interface regions adjacent to water droplets play a vital role in microemulsion-based studies,their widespread applications have not been explicitly evoked owing to their small spaces.Herein,we designed and synthesized a novel double-tailed anionic surfactant(TPE-di-C8SS)by linking the propeller-shaped tetraphenylethylene(TPE)with two octyl chains and an anionic sulfonate headgroup through a methoxy-butyl spacer.The extra spacer and steric hindrance between rigid TPE groups can create the large cavities in hydrophobic interface regions,which we call the hydrophobic interface cages(HICs).The potentials and advantages of HICs in the easily-prepared TPE-di-C8SS microemulsion have been implemented by comparing the extraction efficiency towards cationic rhodamine B with Aerosol OT(AOT)microemulsion.The results provided solid evidence that HICs rather than water droplets contributed to a higher extraction efficiency.This work not only proposes a concept of HICs but also provides a new perspective of their utilization in microemulsion-based applications.

White-Light Electroluminescence with Tetraphenylethylene as Emitting Layer of Aggregation-Induced Emissions Enhancement

Tetraphenylethylene （TPE） based molecules with easy synthesis, good thermal stability, and especially their aggregation-induced emissions enhancement （AIEE） effect recently become attractive organic emitting materials due to their potentially practical application in OLEDs. Herein, the AIEE behaviors of tetraphenylethylene dyes （TMTPE and TBTPE） were investigated. Fabricated luminesent device using TMTPE dye as emitting layer displays two strong emitting bands： the blue emission coming from the first-step aggregation and the yellow emission attrib- uted to the second-step aggregation. Thus, it can be utilized to fabricate the white-light OLEDs （WOLEDs） of the single-emitting-component. A three-layer device with the brightness of 1200 cd·m^-2 and current efficiency of 0.78 cd·A^-1 emits the close to white light with the CIE coordinates of x=0.333 and y=0.358, when applied voltage from 8-13 V, verifying that the TPE-based dyes of AIEE effect can be effectively applied in single-emitting- component WOLEDs fabrication.

Red-emitting tetraphenylethylene derivative with aggregation-induced enhanced emission for luminescent solar concentrators:A combined experimental and density functional theory study

This study examines the use of an aggregation-induced enhanced emission fluorophore(TPE-MRh)to prepare red-emitting luminescent solar concentrators(LSCs)based on poly(methyl methacrylate)(PMMA)and poly(cyclohexyl methacrylate)(PCMA).TPE-MRh is a tetraphenylethylene(TPE)derivative bearing two dimethylamino push groups and a 3-methyl-rhodanine pull moiety,with absorption maxima at around 500 nm and fluorescence peak at 700 nm that strongly increases in solid-state.TPE-MRh displays a typical crystallizationinduced enhanced emission that has been rationalized by modeling the compound behavior in solution and solid-state via density functional theory calculations with the inclusion of the environment.TPE-MRh dispersed into 5×5 cm2 polymer films with a thickness of 25±5μm has revealed a partial fluorescence quenching with fluorophore content.Quantum yields(QYs)below 10%for the 2 wt.%of doping have been addressed to the formation of less emissive micro-sized clusters of fluorophores.PMMA slabs with the same surface size but 3 mm of thickness and 200 ppm of TPE-MRh have provided QY of 36.5%thanks to the attenuation of the detrimental effects of fluorophore aggregation.This feature is reflected in the LSCs performance,with devices achieving the largest power collected by the photovoltaic cell.

Intracellular Self-assembly of TPE-biotin Nanoparticles Enables Aggregation-Induced Emission Fluorescence for Cancer-Targeted Imaging

Fluorogens with aggregation-induced emission (AIE) characteristics have recently been widely applied for studying biological events, and fluorogens with “smart” properties are especially desirable. Herein, we rationally designed and synthesized a biotinylated and reduction-activatable probe (Cys(StBu)-Lys(biotin)-Lys(TPE)-CBT (1)) with AIE properties for cancer-targeted imaging. The biotinylated probe 1 can be actively uptaken by the biotin receptor-overexpressing cancer cells, and then “smartly” self-assemble into nanoparticles inside cells and turn the fluorescence “On”. Employing this “smart” strategy, we successfully applied probe 1 for cancer-targeted imaging. We envision that this biotinylated intelligent probe 1 might be further developed for cancer-targeted imaging in routine clinical studies in the near future.

Enantioselective recognition based on aggregation-induced emission

Chirality is one of the most important features of the nature.The recognition of enantiomers plays significant roles in the field of life science,pharmaceutical analysis and food chemistry.Among various recognition methods,fluorescence spectrometry has attracted much attention of researchers thanks to its high sensitivity and easy operation.Compared with traditional fluorescent probes,chiral molecules with aggregation-induced emission(AIE)have drawn increasing interests due to their huge potential in high-efficiency chemo/biosensors and solid emitters.Chiral AIE luminogens(AIEgens)can not only discriminate two enantiomers with excellent enantioselectivity,but also show general applicability for many chiral analytes,such as chiral acids,amino acids,amines,alcohols.In this review,we mainly summarized the recent development of chiral probes with AIE properties,including chiral tetraphenylethylene(TPE)derivatives,α-cyanostilbene derivatives,Schiff base derivatives and other AIEgens.Their synthetic routes,recognition capabilities and possible working mechanisms were well discussed.It is envisioned that the present review can give some significant guidance for design and synthesis of chiral AIEgens with good enantioselectivity and inspire more readers to join the research of chiral AIE.

Vinylpyridine-and vinylnitrobenzene-coating tetraphenylethenes：Aggregation-induced emission (AIE) behavior and mechanochromic property

Two functional tetraphenylethylene derivatives modified by vinylpyridine and vinylnitrobenzene,respectively, were synthesized by Heck coupling reaction. Their optical behaviors were investigated. The results showed they had AIE activity in solution. The property in solid state displayed that both of them had reversible mechanochromism. Upon grinding, their fluorescence spectra showed around 13–40nm red-shift, and could return to the original state after solvent fuming. We believe that this work will be helpful for the design of stimuli-responsive materials in future.

Synthesis of novel thieno-[3,4-b]-pyrazine-cored molecules as red fluorescent materials

Two novel thieno-[3,4-b]-pyrazine-based molecules, TP-E and TP-O, were designed and synthesized for potential application as red fluorescent emitters. The bulky tetraphenylethylene groups were attached at the periphery of the thieno-[3,4-b]-pyrazine core to form the non-planar molecules, as efficient solid- state emitting materials. The peripheral groups were grafted to the emissive core through either a conjugated acetylene bond, or a non-conjugated ether bond. These molecules exhibit strnng red fluorescence in both dilute solutions and in thin films with large Stokes shifts of over 100 nm. The cyclic voltammetry measurements showed the reversible oxidation and reduction behavior for both compounds. All these properties indicate the two compounds are possible functional materials for use in ontoelectronic devices.

White light emission from AIE-active luminescent organic materials

Fluorescent organic materials that exhibit unique aggregation-induced emission have been utilized for various applications,including white light emission(WLE).The materials typically rely on composite designs involving a mixture of compounds emitting at different wavelengths of light.To overcome the limitations offered by the design of such composite mixtures,tremendous efforts were also emphasized in developing single-molecule substrates that emit white light.The white light by either method is typically controlled by the solvent polarity,energy and charge transfer,host-guest interactions,gelation,or embedding in the polymer or organic frameworks.This article briefly reviews various molecules exhibiting aggregation-induced emission behavior and emitting white light.