Two-color emissive AIEgens with anti-Kasha property for dual-organelle imaging and phototherapy

Despite the rapid development of probes for targeting single organelle, the construction of robust dual-organelle targeting probes with multicolor emission was rarely reported. Herein, two dual-emissive aggregation-induced emission luminogens(AIEgens)with donor-π-acceptor structures were designed and synthesized, namely QT-1 and QF-2. Both two AIEgens exhibited excitation wavelength-dependence defying the Kasha's rule, and could stain lipid droplets(LDs) and mitochondria in blue and red fluorescence, respectively. Moreover, thanks to the near-infrared emission and abundant reactive oxygen species(ROS) generation efficiency of QT-1, it was chosen as a photodynamic therapy agent to selectively kill cancer cells from normal cells. Upon light irradiation, an obvious decrease of mitochondrial membrane potential(MMP) and serious change of mitochondrial shape in cells were observed, which corresponded to the efficient inhibition of tumor growth in vivo. This work afforded a promising strategy for the construction of multicolor emission by tuning anti-Kasha behaviors and expanding their application in dualorganelle targeting-based phototheranostics.

AIEgen configuration transition and aggregation enable dual prompt emission for single-component nondoped white OLEDs

The dual emission(DE)feature in materials holds great potential to revolutionize the development of one-component system white organic lightemitting diodes(WOLEDs).However,the reported DE materials remain scarce owing to the formidable challenge of breaking Kasha’s rule and managing the intricate energy/charge transfer processes.Herein,we have introduced a groundbreaking DE AIEgen,2CzAn-TPE,which possesses a simple structure and undergoes Z-to-E isomerization and exhibits yellow and red fluorescence powders for pre-and post-sublimation,respectively.With relatively lower potential energy,Z-conformation((Z)-1,2-diphenyl-1,2-bis(4-(10-(9-phenyl-9H-carbazol-3-yl)anthracen-9-yl)phenyl)ethene)of 2CzAn-TPE can be readily transformed into E-conformation((E)-1,2-diphenyl-1,2-bis(4-(10-(9-phenyl-9Hcarbazol-3-yl)anthracen-9-yl)phenyl)ethene)via vacuum sublimation.The utilization of X-ray diffraction and grazing-incidence-wide-angle X-ray scattering techniques confirms the structural transformation,while the crystallographic analysis reveals the establishment of numerous intermolecular CH⋅⋅⋅πinteractions between the tetraphenylethene(TPE)moiety and both the anthracene and carbazole units.This allows a densely packed molecular arrangement,thereby offering propitious conditions for excimer generation in the E-conformation aggregated state.By utilizing the sublimated 2CzAn-TPE as an emitter,a nondoped one-component WOLED was prepared,exhibiting an exceptionally high external quantum efficiency(EQE)of 5.0%,which represents one of the highest performances among all one-componentWOLEDs.This research introduces a novel,simple,and efficient approach to realize highly efficient one-molecule WOLEDs.

Sky-Blue Aggregation-Induced Delayed Fluorescence Luminogens with High Horizontal Dipole Orientation for Efficient Organic Light-Emitting Diodes

Efficient and stable blue luminescent organic materials are highly demanded in the field of organic light-emitting diodes(OLEDs)but still remain challenging.In this work,two new sky-blue luminescent molecules comprised of electron acceptor of benzophenone and electron donors of spiro[acridine-9,9'-fluorene]and carbazole are designed and synthesized,and their thermal stability,electrochemical behaviors,photophysical properties,carrier transport ability and electroluminescence performance are investigated.

A Versatile Tetraphenylethene Derivative Bearing Excitation Wavelength Dependent Emission,Multistate Mechanochromism,Reversible Photochromism,and Circularly Polarized Luminescence and Its Applications in Multimodal Anticounterfeiting

Multimodal anticounterfeiting has become increasingly challenging in modern society to guarantee information security and the safety of property.In this study,a versatile cholesterol-containing tetraphenylethene derivative is shown to have multiple optical properties,including stimuli-responsive fluorescence,reversible photochromism,excitation wavelength dependent luminescence,and circularly polarized luminescence.After the application of diverse processing methods(writing,screen painting,drawing,and pyrography),we found that this molecule can serve as an anticounterfeiting toolbox to provide rich anticounterfeiting effects through the synergistical use of multiple optical properties.This work offers important insight for designing novel small organic molecules for advanced multimodal anticounterfeiting technology.

Towards Efficient Blue DelayedFluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Constructing blue thermally activated delayedfluorescence materials for high-performance organic light-emitting diodes(OLEDs)remains challenging due to the intrinsically strong intramolecular charge transfer nature of the nearly orthogonal connection of electron donor(D)and acceptor(A),which results in long-wavelength emission.Herein,an effective delayed-fluorescence design strategy of modulating D–A torsion angles is proposed and efficient sky-blue,pure-blue,and deep-blue delayed-fluorescence molecules consisting of a xanthenone acceptor and carbazole-based donors are created by decreasing the torsion angles.They exhibit strong delayed fluorescence with high photoluminescence quantum yields of 85–94%in doped films,and their delayed-fluorescence lifetimes are elongated from 1.0 to 27.6μs as the torsion angles decrease.These molecules can function as excellent emitters in OLEDs,providing efficient electroluminescence peaking at 442 nm(CIEx,y=0.15,0.08),462 nm(CIEx,y=0.15,0.18),and 482 nm(CIEx,y=0.17,0.30)with state-of-the-art external quantum efficiencies of up to 22.2%,33.7%,and 32.1%,respectively,demonstrating the proposed molecular design for efficient blue delayed-fluorescence molecules is successful and promising.

An efficient aggregation-enhanced delayed fluorescence luminogen created with spiro donors and carbonyl acceptor for applications as an emitter and sensitizer in high-performance organic light-emitting diodes

Organic light-emitting diodes(OLEDs)fabricated using organic thermally activated delayed fluorescence materials as sensitizers have recently achieved significant advancements,but the serious efficiency roll-offs are still troublesome in most cases.Herein,a tailor-made multifunctional luminogen SBF-BP-SFAC containing 9,9′-spirobifluorene(SBF)and spiro[acridine-9,9-fluorene](SFAC)as electron donors and carbonyl as an electron acceptor is synthesized and characterized.SBF-BPSFAC has the advantages of high thermal stability,aggregation-enhanced delayed fluorescence,and balanced carrier transport ability,and prefers horizontal dipole orientation.Highly efficient OLEDs employing SBF-BP-SFAC as an emitter radiate intense cyan light with outstanding external quantum efficiencies(ηexts)of up to 30.6%.SBF-BP-SFAC can also serve as an excellent sensitizer for orange fluorescence,phosphorescence,and delayed fluorescence materials,providing excellent η exts of up to 30.3% with very small efficiency roll-offs due to the fast Förster energy transfer as well as exciton annihilation suppression by bulky spiro donors.These outstanding performances demonstrate the great potential of SBF-BP-SFAC as an emitter and sensitizer for OLEDs.

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。

Electronic effect on the optical properties and sensing ability of AIEgens with ESIPT process based on salicylaldehyde azine

Two novel AIE-active salicylaldehyde azine(SAA) derivatives with a typical excited-state intramolecular proton transfer(ESIPT) process are prepared by introducing electron-withdrawing and donating groups at para-position of phenolic hydroxyl group(CN-SAA and TPA-SAA). The effect of the proton activity in SAA framework on their optical behaviors is investigated spectroscopically. The results from NMR and solvation measurements show that the proton of phenolic hydroxyl group has higher activity when there are electron-withdrawing groups, and the absorption and fluorescence spectra in buffers with different pH also provide the same results. After inviting F. as a nucleophilic probe, this proton activity difference in CN-SAA and TPA-SAA becomes more obvious. The potential application of both molecules is investigated. TPA-SAA exhibits good quantitative sensing ability towards F. with a fluorescence "turn-on" mode, whereas the aggregates of TPA-SAA can selectively and sensitively detect Cu2+ in aqueous solution. From these results, a structure-property relationship is established: the occurrence of ESIPT process will become much easier when linking electron-withdrawing groups at the para-position of phenolic hydroxyl group(e.g., CN-SAA),and it is better to introduce electron-donating groups to enhance the sensing ability towards ions(e.g., TPA-SAA). This work will provide guidance for further design and preparation of AIE-active luminogens with ESIPT process for sensing applications.

A Silole-Based Efficient Electroluminescent Material with Good Electron-Transporting Potential

A new silole derivative, 2,5-bis（7-（dimesitylboranyl）-9,9-dimethylfluoren-2-yl）- 1 -methyl- 1,3,4-triphenylsilole （（MesBF）2MTPS）, is synthesized and characterized. （MesBF）2MTPS shows a good fluorescence efficiency of 15% in THF solution and a higher efficiency of 86% in solid film, presenting an aggregation-enhanced emission charac- teristic. It is thermally and morphologically stable, with high decomposition and glass-transition temperatures of 257 and 171 ℃, respectively. The LUMO energy level （-2.96 eV） of （MesBF）zMTPS is lower than that of TPBi, revealing its electron-transporting potential. Efficient organic light-emitting diodes （OLEDs） are fabricated using （MesBF）2MTPS as emitter, which radiates yellow light at 554 nm, and affords high maximum luminance, current efficiency, and external quantum efficiency of 48348 cd·m^-2, 12.3 cd·A^-1, and 4.1%, respectively.

Red AIE conjugated polyelectrolytes for long-term tracing and image-guided photodynamic therapy of tumors

Robust photosensitizers with strong red/NIR fluorescence, efficient reactive oxygen species(ROS) generation and high photostability are highly desired for photodynamic therapy(PDT). Herein, three novel red conjugated polyelectrolytes(CPEs) with tetraphenylethene and 2,1,3-benzothiadiazole on the main chains and triphenylphosphonium on the side chains are developed.These CPEs display apparent aggregation-induced emission feature and high fluorescence quantum yields in the aggregated state. They can target lysosome in He La cells for fluorescence bioimaging. By virtue of the good retention effect and high photostability, these CPEs show ultralong-term tracing performance of subcutaneous tumors, and the tumor site can still be visualized for 20 days after injection. Owing to their good biocompatibility and strong ROS generation ability, the image-guided PDT based on these CPEs can effectively inhibit the growth of subcutaneous tumor and significantly prolong the survival of tumor bearing mice. The H&E and IHC staining reveal that the PDT of these CPEs depress the proliferation of tumor cells, and promote apoptosis and necrosis process. These new CPEs may be employed both as fluorescent probes for in vitro and in vivo long-term tracing and as photosensitizers for image-guided PDT of tumors.

Self-healing hyperbranched polytriazoles prepared by metal-free click polymerization of propiolate and azide monomers

The last decade has witnessed the quick develop of self-healing materials. As a newborn strategy, the alternative of irreversible covalent bond formation is, however, to be further developed. In this paper, self-healing hyperbranched poly(aroxycarbonyltriazole)based on such mechanism were prepared by our developed metal-free click polymerization of simplified dipropiolate and triazide. Thanks to their excellent processability and film-forming ability, high quality homogeneous films free from defects were obtained by casting. The cut films could be healed by stacking or pressing the halves together at room temperature and elevated temperature. Thus, this design concept for self-healing materials should be generally applicable to other hyperbranched polymers with reactive groups on their peripheries.

Versatile Aggregation-Enhanced Delayed Fluorescence Luminogens Functioning as Emitters and Hosts for High-Performance Organic Light-Emitting Diodes

Severe efficiency instability is still a huge challenge for most organic light-emitting diodes(OLEDs)based on thermally activated delayed fluorescence(TADF)molecules,frustrating their industrial application.To address this issue,herein we report two robust luminogens,3,6-bis(9,9-dimethylacridin-10-yl)-xanthen9-one(BDMAC-XT)and 3,6-bis(9,9-diphenylacridin-10-yl)-xanthen-9-one(BDPAC-XT),comprised of electron-accepting 3,6-dibromoxanthen-9-one and electron-donating 9,9-dimethyl-9,10-dihydroacridine and 9,9-diphenyl-9,10-dihydroacridine.

Through-Space Conjugation: A Thriving Alternative for Optoelectronic Materials

Efficient electronic coupling is the key to constructing optoelectronic functionalπsystems.Generally,the delocalization ofπelectrons must comply with the framework constructed by covalent bonds(typicallyσbonds),representing classic through-bond conjuga-tion.However,through-space conjugation offers an alternative that achieves spatial electron communica-tionwith closely stacked π systems instead of covalent bonds thus enabling multidimensional energy and charge transport.

Red fluorescent siloles with aggregation-enhanced emission characteristics

Aseries of new red fluorescent siloles consisting of a silole core and dimesitylboranyl substituent connected with a furan,thiophene,and selenophene bridges were synthesized and characterized.The optical properties,electronic structures,and electroluminescence (EL) performances were investigated.The emission wavelengths were red-shifted from the siloles with furan,to those with thiophene,and then selenophene.The thiophene,and selenophene-containing siloles,(MesB)_2DTTPS,and(MesB)_2DSTPS,showed the typical aggregation-enhanced emission (AEE) feature,while furan-containingone,(MesB)_2DFTPS,showed slight emission decrease as the aggregate formation.Theoretical calculations were carried out to explain the difference in the optical properties.Undoped OLEDs using these red siloles as light-emitting layers were fabricated.The device of (MesB)_2DTTPS exhibited the bestper formance.It radiated red ELemission at 589 nm,and afforded good maximum luminance,current,power,and external quantum efficiency of13300cdm^(-2),4.3cd A^(-1),2.9 lmW^(-1),and1.8%,respectively.

New carbazole-substituted siloles for the fabrication of efficient non-doped OLEDs

Luminogenic molecules with aggregation-induced emission(AIE) property are free of aggregationcaused quenching and thus have great potential in the fabrication of efficient non-doped OLEDs. Herein, a series of new carbazole-substituted siloles have been synthesized and characterized. Their crystal and electronic structures, thermal stabilities, electrochemical behaviors, and photophysical properties are thoroughly investigated. These silole derivatives exhibit prominent AIE characteristics with high emission efficiencies in solid films. They can function as light-emitting layers in non-doped OLEDs,affording eminent electroluminescence efficiencies of 17.59 cd/A, 12.55 Im/W and 5.63%, amongst the most efficient non-doped OLEDs based on fluorescent emitters, indicating their promising applications in OLEDs.

Blue fluorophores comprised of tetraphenylethene and imidazole： aggregation-induced emission and electroluminescence

By melting tetraphenylethene （TPE） and 1,2,4,5-tetraphenyl-lH-imidazole （TPI） units together through different linking positions, three new fluorophores are synthesized, and their optical, electronic and electro- luminescence （EL） properties are fully studied. Owing to the presence of TPE unit（s）, these fluorophores are weak emitters in solutions, but are induced to emit strongly in the aggregated state, presenting typical aggregation-induced emission characteristics. The experimental and computational results reveal that different connection patterns between TPE and TPI could impact the molecular conjugation greatly, leading to varied emission wavelength, fluorescence quantum yield and EL performance in organic light emitting diodes （OLEDs）. The fluorophore built by attaching TPE unit to the 1-position of imidazole ring shows bluest fluorescence, and its EL device emits at deep blue region （445 nm; CIE= （0.16, 0.15））. And the device based on the fluorophore by linking TPE to the 2- position of imidazole ring shows EL at 467 nm （CIE= （0.17, 0.22）） with good efficiencies of 3.17 cd.A ^-1, and 1.77%.

Deciphering Benzene-Heterocycle Stacking Interaction Impact on the Electronic Structures and Photophysical Properties of Tetraphenylethene-Cored Foldamers

Conjugation,as an essential chemical term used to describe electron delocalization,can be roughly grouped into two categories,through-bond conjugation(TBC)and through-space conjugation(TSC).A hybrid conjugation system integrating both TBC and TSC is rarely studied and utilized,for lack of a well-established model and difficulty of structure modification and property tuning,despite its theoretical significance and potential applications.Herein,various foldamers with a tetraphenylethene(TPE)core are employed as hybrid conjugation models to investigate structure–property correlation by introducing heterocycles of furan/thiophene into theπ-stacking TSC component.For comparison,two kinds of TPE-cored foldamers with different stacking models,a benzene–heterocycle stacking model and a benzene–benzene stacking model,are designed.Combining experimental measurements and theoretical calculations,the impact of benzene–heterocycle interaction on the hybrid conjugation natures and photophysical properties has been studied systematically.The results reveal that the benzene–heterocycle stacking model can fabricate a hybrid conjugation nature with an improved TSC component to make a more dominant contribution to the electronic transition natures than the benzene–benzene stacking model,leading to the distinguishing photophysical behavior.This work provides valuable guidance for the design of new functional materials with hybrid conjugation systems.

Novel Germoles and Their Ladder-Type Derivatives:Modular Synthesis,Luminescence Tuning,and Electroluminescence

Considerable effort has been devoted to the design of silicon-containingπ-conjugated materials for application in optoelectronic devices and fluorescent bioimaging.However,the synthesis and spectroscopic tuning of germanium(Ge)-conjugated systems are challenging because of the paucity of synthetically useful methods.Herein,we report a simple and effective method of lithium naphthalenide-induced intramolecular cyclization to construct architecturally diverse Ge-containingπ-conjugated molecules,including benzogermoles and their ladder-type derivatives,with high yields of up to 92%.The photophysical properties of these molecules can befinely controlled by the introduction of electrondonating or-withdrawing substituents,and intense luminescence ranging from deep-blue to red regions in the solid state was observed.A quantitative model based on the Hammett constant against the luminescence wavelength showed a good linear correlation,allowing us to reliably predict and design luminescent materials with specific properties for applications.Notably,Ge-bridged ladder-type derivatives exhibited high photoluminescence and efficient deep-blue electroluminescence with good color purity.We believe this study will open a new avenue to organogermanium chemistry and offers greater flexibility for electronic structural tuning.

Controllable Secondary Through-Space Interaction and Clusteroluminescence

Nonconjugated clusteroluminogens(CLgens),such as proteins and polystyrene,have become increasingly important in photophysics.They show many advantages over traditional conjugated dyes with fused aromatic rings in biological applications.However,CLgens have historically been unheeded because of their weak visible emissions in the aggregate state,namely clusteroluminescence(CL).Changing the electronic structures of CLgens by precisely regulating the intramolecular throughspace interaction(TSI)to improve their photophysical properties remains an enormous challenge.Herein,we propose a general strategy to construct a higher-level intramolecular TSI,namely secondary TSI constructed by the primary TSI and a TSI linker,in multi-aryl-substituted alkanes(MAAs).By introducing methyl and phenyl into 1,1,3,3-tetraphenylpropane,the modified MAAs show efficient CL with high luminescence quantum yield(-40%)and long emission wavelength(-530 nm).Then,comprehensive experiments and theoretical studies demonstrate that molecular rigidity and overlap of subunits play pivotal roles in improving these hierarchical TSIs.This work not only provides a feasible strategy to achieve controllable manipulation of hierarchical TSIs and CL but also establishes comprehensive TSI-based aggregate photophysics.