Design, Synthesis And Application Of Organic Photochromic Materials With Aggregation-induced Emission Based On Thiophene Groups

Organic photochromic molecules as an important light-responsive functional material have received plenty of research interest because they show unique photo-induced coloration and can be widely used to design multifunctional molecular machines and smart materials.However,these traditional photochromic materials show Aggregation-Induced Quenching(ACQ)in aggregate or solid state,which greatly limits their performance in practical applications.Fortunately,the Aggregation-Induced Emission(AIE)proposed by Tang group can effectively solve the limitations caused by ACQ in traditional photochromic molecules.The introduction of AIE makes the photochromic system have more fascinating solid-state fluorescence characteristics.Such reversible photochromic molecules with solid-state fluorescence are of great value and perspective in various surface-involved practical applications.Currently,a series of AIE-active photochromic materials have been reported,but most of them cannot be photochromic in a controlled manner.The results show that these compounds show excellent photochromic and photochromic properties,and multicolor conversion can be achieved by adjusting different excitation wavelengths.The main contents of this paper are as follows:In this paper,we propose a general strategy for designing reversible photochromic molecules with solid-state fluorescence by introducing photoactive groups into the AIE-active molecular skeleton.The photoactive thiophene group was simply introduced into the tristyrene skeleton with AIE properties to design reversible photochromic molecules with bistable isomers,which have unique aggregation-induced emission and reversible photochromic behavior,and have potential applications in optical switching dual-mode patterning and advanced anti-counterfeiting.Based on the above strategy,by introducing different substituent structures on the original tetraarylethylene skeleton,the absorption and fluorescence emission properties of different wavelengths can be controlled.the results show that these compounds showed good photochromic properties and light color changing nature,through the regulation of different excitation wavelength,can realize the color conversion.The main contents of this paper are as follows:(1)We propose a general strategy to design reversible photochromic molecules with solid-state fluorescence by introducing photoactive thienyl and benzothienyl groups into an AIE-active molecular skeleton.The combination of a thienyl or benzothienyl group and a triphenylethene in the right manner enables the molecules to possess unique aggregation-induced emission properties and reversible photo-controlled changes in color and fluorescence in solid state.Theoretical analysis reveals that photo-triggered cyclization and cycloreversion reactions are responsible for the reversible photochromism and photoinduced fluorescence switching,and the enlargement of the conjugation of the introduced photoactive units can significantly promote the cyclization reactions and the photochromic processes.The excellent performance of these photochromic molecules with aggregation-induced emission activity in a photo-switchable patterning paper and multiple encryptions of anti-counterfeiting of a banknote demonstrates that they are perfectly suited for surface-involved photo-controlled applications such as information storage and data encryption.(2)A group of photochromic molecules with different colors were designed through introducing photoactive units into an AIE-active molecular skeleton,and the dual regulation of aggregation-induced emission and photochromic properties are achieved.Meanwhile,multicolor photochromic excited by different wavelengths is realized in a multi-component system composed of these compounds of different colors.Studies have shown that the bonding position of the photoactive unit and the AIE molecular skeleton can significantly affect the photophysical properties and photochemical behavior of the compound,and the difference between the two stems from the activity rate of the photocyclization reaction.The electronic effect and steric hindrance of substituents are simply used to regulate the photocyclization activity of compounds,so as to realize the regulation of photochromic properties and fluorescence properties of these compounds.The exploration of structure-activity relationship provides new perspectives and ideas for the subsequent construction of intelligent and efficient AIE photochromic materials.In summary,we propose a strategy of introducing photoactive groups into the aggregation-induced emission molecular framework to design photochromic materials with aggregation-induced emission properties,and successfully designed and synthesized a series of tetraarylethylene derivatives with solid-state fluorescence and reversible photochromic properties.At the same time,by changing substituent on the side chain thiophene,the fluorescence emission and photochromic color can be controlled.Because this type of AIE-active photochromic molecule has unique aggregation-induced emission characteristics and reversible photo-controlled changes in color and fluorescence in solid state,it has great application prospects in information storage and multiple anti-counterfeiting applications.