Turn-on fluorescence in tetraphenylethylene-based metal-organic frameworks: an alternative to aggregation-induced emission

Coordinative immobilization of functionalized tetraphenylethylene within rigid porous metal-organic frameworks (MOFs) turns on fluorescence in the typically non-emissive tetraphenylethylene core. The matrix coordination-induced emission effect (MCIE) is complementary to aggregation-induced emission. Despite the large interchromophore distances imposed by coordination to metal ions, a carboxylate analogue of tetraphenylethylene anchored by Zn(2+) and Cd(2+) ions inside MOFs shows fluorescence lifetimes in line with those of close-packed molecular aggregates. Turn-on fluorescence by coordinative ligation in a porous matrix is a powerful approach that may lead to new materials made from chromophores with molecular rotors. The potential utility of MCIE toward building new sensing materials is demonstrated by tuning the fluorescence response of the porous MOFs as a function of adsorbed small analytes.     

四苯乙烯的合成、表征及在爆炸物检测中的应用 ——介绍一个大学化学综合实验

因具有聚集诱导发光特性、螺旋桨结构的四苯乙烯及其衍生物,在有机光电材料、荧光传感和生物成像等领域表现出优异的荧光性能。本实验以二苯甲酮为原料,利用McMurry偶联反应合成四苯乙烯。采用萃取、干燥和柱层析等手段对产物进行分离和纯化,通过熔点测定、核磁共振氢谱、核磁共振碳谱和质谱对其结构进行表征后,使用苦味酸作为模型化合物,利用荧光光谱测定其对爆炸物的荧光检测极限。本实验寓科研热点于实验教学中,不仅提高了学生的实验操作技能,而且有助于学生了解具有聚集诱导发光性能的四苯乙烯及其衍生物的研究现状和应用前景,激发了学生的科研兴趣和创新意识。     

Triptycene-scaffolded tetraphenylethylenes with irregular temperature-dependence AIE

A series of new tetraphenylethylene monomer, dimer and three-dimensional trimer based triptycene-bridged triphenylethenes has been constructed. Their structures were clearly confirmed and the irregular fluorescent behaviors at different temperatures and solvents were investigated. Results showed the new tetraphenylethylenes performed remarkable aggregation-induced emission (AIE) properties and the emission intensities are dependent on temperature and viscosity. Compared with the model tetraphenylethylene without connecting triphenylethylene, the fluorescence quantum yields of the titled triptycene-scaffolded tetraphenylethylenes in aggregation are greater than tetraphenylethylene and increased as the increasing of the triphenylethylene units.     

Tetrapyridyl tetraphenylethylenes: supramolecular building blocks with aggregation-induced emission properties

Two tetrapyridyl-substituted tetraphenylethylenes have been prepared via Suzuki coupling between tetrabromo tetraphenylethylene and 3- or 4-pyridine boronic acid. Both compounds exhibit aggregation-induced emission as determined by solid state fluorescence spectroscopy and solution phase fluorescence measurements performed in aqueous/organic solvent mixtures. Solution phase fluorescence was also found to be switchable as a function of pH. 3-Pyridyl-substituted tetraphenylethylene has been structurally characterized by X-ray crystallography.     

A new ligand and its complex with multi-stimuli-responsive and aggregation-induced emission effects

A new ligand containing tetraphenylethylene and terpyridine moieties, and its zinc ion complex were synthesized. Both of them exhibit an aggregation-induced emission effect. Their colors and emissions can be smartly switched by various external stimuli including grinding, heating and solvent-fuming, as well as exposure to acid and base vapors.     

A New Tetraphenylethylene‐Derived Fluorescent Probe for Nitroreductase Detection and Hypoxic‐Tumor‐Cell Imaging

The fluorescence detection of nitroreductase (NTR) and evaluation of the hypoxia status of tumor cells are vital, not only for clinical diagnoses and therapy, but also for biomedical research. Herein, we report the synthesis and application of a new fluorometric “turn‐on” probe for the detection of NTR ( TPE?NO₂ ) that takes advantage of the aggregation‐induced emission of tetraphenylethylene. TPE?NO₂ can detect NTR at concentrations as low as 5 ng mL^?1 in aqueous solution. The detection mechanism relied on the aggregation and deaggregation of tetraphenylethylene molecules. Moreover, this fluorescent probe can be used to monitor the hypoxia status of tumor cells through the detection of endogenous NTR.     

Synthesis and photophysical properties of tetraphenylethylene-based conjugated dendrimers with triphenylamine core

Two new conjugated dendrimers bearing a tetraphenylethylene moiety as dendrons and triphenylamine as a core have been synthesized through a convergent synthetic strategy using threefold Heck/threefold Sonogashira coupling reaction. These dendrimers showed excellent solubility in common organic solvents and emit light in the blue and violet regions.     

A Fluorogenic Probe with Aggregation‐Induced Emission Characteristics for Carboxylesterase Assay through Formation of Supramolecular Microfibers

Herein, we report a novel fluorescent “light‐up” probe useful for carboxylesterase assay that is based on a tetraphenylethylene derivative containing carboxylic ester groups. The specific cleavage of the carboxylic ester bonds by carboxylesterase results in the generation of a relatively hydrophobic moiety that self‐assembles into supramolecular microfibers, thus giving rise to “turn‐on” fluorescent signals. A high sensitivity towards carboxylesterase was achieved with a detection limit as low as 29 pM , which is much lower than the corresponding assays based on other fluorescent approaches.     

Investigation of radical cation in electrophilic fluorination by ESI-MS

Reaction solutions of selectfluor (1) with triphenylethylene (4a) and tetraphenylethylene (4b) were monitored by ESI-MS and ESI-MS/MS. Detection and characterization of the key radical cationic intermediates 5a.+ and 5b.+) fully supports the SET mechanism in electrophilic fluorination as depicted above. [reaction: see text]     

Reevaluating the Solution Photophysics of Tetraphenylethylene at the Origin of their Aggregation-Induced Emission Properties

Although tetraphenylethylene (TPE) and its derivatives have been the most commonly used building blocks in the construction of molecules with aggregation-induced emission (AIE) properties, no absolute consensus exists regarding the mechanisms at the origin of the phenomenon. Restriction of intramolecular rotations (RIR) of peripheral phenyls has historically been a dominant paradigm, which has served as a valuable guideline in the molecular engineering of AIEgens. Yet, an increasing number of recent works have established that photoisomerization or photocyclization may actively participate in the nonradiative dissipation of the excitation energy. In this paper, the first experimental evaluation of the quantum efficiencies of these different processes is reported, and photoisomerization is shown to be by far the dominant photophysical pathway in solution, accounting for virtually all nonradiative decay of the molecule‘s excited state in degassed solution.     

Aggregation‐Induced Emission and Aggregation‐Promoted Photo‐oxidation in Thiophene‐Substituted Tetraphenylethylene Derivative

Aggregation‐induced emission combined with aggregation‐promoted photo‐oxidation has been reported only in two works quite recently. In fact, this phenomenon is not commonly observed for AIE‐active molecules. In this work, a new tetraphenylethylene derivative (TPE‐4T) with aggregation‐induced emission (AIE) and aggregation‐promoted photo‐oxidation was synthesized and investigated. The pristine TPE‐4T film exhibits strong bluish‐green emission, which turns to quite weak yellow emission after UV irradiation. Interestingly, after solvent treatment, the weakly fluorescent intermediate will become bright‐yellow emitting. Moreover, the morphology of the TPE‐4T film could be regulated by UV irradiation. The wettability of the TPE‐4T microcrystalline surface is drastically changed from hydrophobic to hydrophilic. This work contributes a new member to the aggregation induced photo‐oxidation family and enriches the photo‐oxidation study of tetraphenylethylene derivatives.     

Synthesis of new chiral fluorescent sensors and their applications in enantioselective discrimination

New chiral fluorescent sensors derived from tetraphenylethylene and proline hydrazide were synthesized and applied in the chiral recognition of various chiral compounds, including unprotected amino acids, acidic compounds, chiral amines and even neutral alcohols. These results demonstrated that the excellent enantioselective response ability to various chiral substrates could be attributed to the –NH moieties of pyrrolidine ring and thiourea unit which acted as hydrogen-bonding donors. This result is of potential significance in enantiomeric discrimination and high-throughput analysis of the enantiomeric purity of chiral guests.     

The influence of an intramolecular relaxation process on the frequency-time behaviour or the fluorescence of tetraphenylethylene in highly viscous solutions

Within a certain viscosity range the fluorescence decay time of tetraphenylethylene was found to vary considerably with respect to the selected emission wavenumber interval. This anomalous behaviour is explained by an intramolecular conformation change of the excited state during emission.     

Water‐soluble AIE‐Active Fluorescent Organic Nanoparticles: Design,Preparation and Application for Specific Detection of Cysteine over Homocysteine and Glutathione in Living Cells

Water‐soluble ratiometric AIE‐active fluorescent organic nanoparticles 2OA‐FON for the specific sensing of cysteine over other biothiols are reported. The obtained amphiphilic probe included olefin aldehyde as recognizing unit, tetraphenylethylene as fluorescence reporter and lactose moiety as a hydrophilic group. This work provides a general design strategy based on the introduction of a sugar moiety into a hydrophobic AIEgen to develop ratiometric water‐soluble fluorescent organic nanoparticles.     

Highly selective fluoride sensing via chromogenic aggregation of a silyloxy-functionalized tetraphenylethylene (TPE) derivative

A silyloxy-functionalized tetraphenylethylene (TPE) derivative shows a remarkable change in the absorption spectrum on deprotection with fluoride ions. The reaction process is highly selective for fluoride and the resulting charge transfer band results in a bright green solution. A simple selective visual assay of aqueous fluoride ions was also obtained by the impregnation of cellulose strips with the TPE derivative.     

Turn-on of the fluorescence of tetra(4-pyridylphenyl)ethylene by the synergistic interactions of mercury(II) cation and hydrogen sulfate anion

The fluorescence of tetra(4-pyridylphenyl)ethylene (1) can be switched on significantly by the synergistic interactions of Hg(2+) and HSO(4)(-) based on a new aggregation mechanism for tetraphenylethylene molecules.     

苯基取代乙烯类化合物在硅胶表面敏化光氧化反应的研究

随着人们对吸附态有机分子光谱性质的研究的不断深入,光化学中的一个重要方面——表面光化学,也得到了很大的发展。在固体表面上,人们观察到了许多与溶液中不同的现象。这主要是由于固体表面上常常表现出某种特有的吸附特性,从而对被吸附物质的能级状态和分子结构产生影响,进而改变了它们的反应性能,这类报道已有很多^[1]。     

Fluorescent "light-up" bioprobes based on tetraphenylethylene derivatives with aggregation-induced emission characteristics

Aggregation in poor solvents and complexation with calf thymus DNA and bovine serum albumin turn "on" the fluorescence of tetraphenylethylene derivatives, due to the restriction of intra-molecular rotations of the dyes in the aggregates and complexes.     

A new ratiometric Ag+ fluorescent sensor based on aggregation-induced emission

The novel tetraphenylethylene(TPE)-based sensor 1 bearing bis(2-pyridin-2-ylmethyl)amine (BPA) units linked with triazole moieties could be obtained by click reaction efficiently. The results show that 1 can demonstrate a Ag⁺-specific emission shift and highly sensitive fluorescent enhancement with a 1:2 binding ratio based on the aggregation-induced emission mechanism. Compound 1 is shown to behave as a ratiometric sensor.     

Efficient photocatalytic oxygenation of aromatic alkene to 1,2-dioxetane with oxygen via electron transfer

[reaction: see text] Photocatalytic oxygenation of tetraphenylethylene (TPE) with oxygen occurs efficiently via electron-transfer reactions of TPE and oxygen with a photogenerated electron transfer state of 9-mesityl-10-methylacridniium ion, followed by the radical-coupling reaction between TPE radical cation and O2*- to produce 1,2-dioxetane selectively. The further photocatalytic cleavage of the O-O bond of dioxetane affords benzophenone as the final oxygenated product.