Tetraphenylethene Derivatives:Design,Synthesis And Properties

The exploitation of highly emissi,ve fluorescent molecules has attracted considerable research interests,owing to their broad applications in photoelectronic materials,biological sensors,chemosensors,luminescent materials,and so on.However,most of the organic fluorescent dyes are weakly emissive or non-emissive in the solid state due to the notorious aggregation caused quenching(ACQ)effect.Obviously,the ACQ effect is very disadvantageous to the practical application of fluorescent organic materials.Fortunately,Tang’s group discovered an aggregation induced emission(AIE)phenomenon which is exactly opposite to ACQ.Tetraphenylethene(TPE)is a typical AIE compound,and it has been proved that restricting intramolecular rotation(RIR)was the main reason leading to its AIE effect.In the construction of AIE molecules,attaching TPE to the skeleton of traditional ACQ dyes is an efficience strategy.On the other hand,TPE possesses good applicationprospect in smart materials.Based on this,in this paper,we attempt study the structure-active relationship between the molecular structure and emission character in the aggregation state by attaching TPE unit to the skeleton of traditional ACQ dyes and explore their potential application in imaging,sensor,and functional materials.The main research contents are shown as following:1.The amino containing TPE units are attached to molecular section of naphthalimide and fourteen target compounds have been synthesized and well-characterized by 1H NMR spectroscopy,13C NMR spectroscopy,mass spectrometry,elemental analysis and X-ray single crystal diffraction.The study of phototphysical properties indicate that when TPE is connected to the dyes in conjugated method,molecules will exhibit the RIR effect induced AIE character;when there is no conjugated effect,the photophysical properties of the molecule are depended on the intramolecular charge transfer(ICT)effect,which is produced between the amino and naphthalimide unit and will further lead to ACQ character.On the other hand,when aniline was introduced at 4th position of naphthalimide unit,molecules will exhibit the twisted intramolecular charge transfer(TICT)effect induced AIE character.The study of solid-state fluorescence properties indicate that compoundsⅡ-a-1,Ⅱ-c-1,Ⅱ-b-3 exhibite grinding induced emission enhancement phenomenon.This result provides a new idea for modulating the emission character of fluorescence dyes with D-A structure.2.Amion containing TPE is attached to different fluorescence dyes and eleven target compounds have been synthesized and well-characterized by 1H NMR spectroscopy,13C NMR spectroscopy,mass spectrometry,elemental analysis and X-ray single crystal diffraction.The study of phototphysical properties indicate that not all of the compounds exhibite AIE phenomenon when TPE is connected to the dyes in conjugated method.The AIE effect is in relationship with the ability of TPE to dissipate the molecular excited state energy and the formed molecular aggregation state.On the other hand,when TPE is connected to the dyes in non-conjugated method and there exist no intramolecular fluorescence resonance energy transfer(FRET)effect,molecule can exhibite AIE character.Based on this,AIE compounds with blue,blue-green,green,pinkish-orange,deep red and NIR fluorescence are prepared and applied in cell imaging.What’s more,TPE can endow fluorescence dyes with stimuli-response ability,for example,compound Ⅲ-1-a exhibite a reversible mechanofluorochromic behavior,and Ⅲ-2-b exhibite UV-light induced emission enhanced behavior.This research provides a new idea for improving the luminescent properties of fluorescence dyes and the design of stimuli-response materials.3.TPE is introduced to a sulfonamide unit containing naphthalimide and conpound Ⅳ-1 is synthesized and well-characterized by 1H NMR spectroscopy,13C NMR spectroscopy,mass spectrometry,elemental analysis and X-ray single crystal diffraction.Studying of the photophysical properties indicated that,Ⅳ-1 not only exhibite AIE character in DMSO/water mixture,but also change its solid fluorescence color from yellow-green to orange under grinding.On the other hand,in CTAB containing DMSO/water mixture,Ⅳ-1 can be used in the specific detection of GSH.To further improving the recognition result,we attached Ⅳ-1 on the surface of nanogel and synthesized the nanogel probe poly-PEG-PEI/TPE,the nanogel probe was successfully applied in the dectection of GSH in water and cell,subsequently.This research provides a new idea for construction of TPE derivative with multiple functions.4.TPE is introduced to acicd/base-responsive molecule shuttle and target compounds Ⅴ-1-a andⅤ-1-b are synthesized and well-characterized by 1H NMR spectroscopy,13C NMR spectroscopy,mass spectrometry and elemental analysis.Structural analysis reveals that the macrocycle host of compound Ⅴ-1-a will combine with the ammonium site of the guest in acidic condition,and the host is close to the TPE unit.However,the macrocycle host of compound Ⅴ-1-b will locate at the site of the amide,which is far away from the TPE unit in the alkaline condition.The study of the AIE behavior indicate that compared to Ⅴ-1-b,compound Ⅴ-1-a is easyer to form the aggregation state in the mixture of acetonitrile and water,which can be attributed to stronger interaction between the macrocycle host and TPE unit when the host combine with ammonium site.The presented results may establish a novel perspective for the design and construction of AIE-active mechanically interlocked molecules5.TPE is introduced to the photochromic dithienylethene unit,compounds Ⅵ-1-a,Ⅵ-1-b andⅥ-1c are synthesized and well-characterized by]H NMR spectroscopy,13C NMR spectroscopy,mass spectrometry,elemental analysis and X-ray single crystal diffraction.The study of photophysical properties indicate that all of those molecules exhibite AIE character because of the introduction of TPE.What’s more,compound VI-1-a exhibites a reversible mechanofluorochromic behavior.On the other hand,the introduced dithienylethene endows those molecules with photochromic properties.Interestingly enough,in the solid state,grinding could inhibit the photochromic property of VI-1-a,however the followed annealing process could recover its photo-responsive character.Mechanism research reveals that the solid of VI-1-a can only response to UV light when it is in the crystal state,once it is converted to amorphous state,the photochromic properties will be locked because of the molecular conformation change.But compounds VI-1-b and VI-lc don’t possess the responsiveness like VI-1-a.This research is of great significance in the construction of functional dithienylethene derivative.