Synthesis And Properties Of Near Infrared Optical Functional Molecules Of Terrylenediimide

Rylenediimides are a kind of important chromophores.Among them,terrylenediimide(TDI)as one of the series of higher rylenediimides,exhibits strong red absorption and far-red emission and possesses excellent thermal,chemical and photo stability,which can be well applied in the fields of single molecule spectroscopy,biological imaging and photoelectric devices after appropriate modification.However,the study of TDI is still in its infancy,far inferior to its lower homolog naphthalenediimide(NDI)and perylenediimide(PDI).Although it has been well used in single molecule spectroscopy,but rarely used in other fields.Therefore,we design and synthesis of a series of new near-infrared organic optical functional molecules: tetraphenylethene(TPE)or dithienylethene(DTE)covalent coupling of TDI near-infrared fluorophore.We have systematically studied their properties such as aggregation-induced emission(AIE),photochromism and fluorescence switch,light-controlled self-assembly,visible light sensitivity and near-infrared solid-state photoswitch and expanded the applications of TDI in erasable optical storage,fluorescent nondestructive readout,all-optical transistor and super-resolution fluorescence imaging.The main research contents are as follows:(1)We have summarize a kind of synthesis method with mild conditions,wide applicability,high yield and easy to prepare TDI in large quantities,that is,the Suzuki coupling reaction with borate ester of naphthalimide as the intermediate and the cyclic reaction with potassium carbonate as the base in ethanolamine.The experimental conditions of TDI bromination has been optimized for the functionalization of TDI.(2)In order to improve the solid-state luminescence performance of TDI,we have integrated TDI near-infrared fluorophore and bulk AIE-active TPE into a single molecule by covalently binding one TDI and four TPE molecules.We designed two styles of covalent binding: one is π-conjugated(TDI-4TPE)while the other is O-bridged non-conjugated(TDI-O-4TPE).Using this approach,the compact stacking between molecules has been well limited and the typical aggregation-induced quenching(ACQ)TDI has been successfully converted to a near-infrared AIE luminogen.The emission of TDI-4TPE is completely located in the first near-infrared region,and with a maximum emission wavelength up to 800 nm,which has not been reported before to the best of our knowledge.(3)In order to regulate the near infrared emission of TDI,a series of near infrared fluorescent molecular switches(TDI-nDTE,n = 2,3,4 represent the number of DTE in a single molecule)of multiple photochromic DTE units covalently coupled to a single TDI fluorophore via oxygen bridge bond has been designed and synthesized.They have excellent photochromic and fluorescence switching properties in different media.Increasing the number of DTE can effectively improve the fluorescence efficiency.Among them,TDI-4DTE possesses the best optical properties with a fluorescent on/off ratio up to 4810.Fluorescence quenching is the result of fluorescence resonance energy transfer(FRET)combined with photoinduced intramolecular charge transfer(PET)mechanism.TDI-4DTE shows a fluorescent nondestructive readout capability in polyacrylic acid(PMA)films,and upon 720 nm light irradiation,the photoisomerization of TDI-4DTE is not occur.The erasable optical storage and fluorescent nondestructive capacity have been demonstrated in terms of fluorescence intensity,macro and micro fluorescence imaging under three light beams.In addition,TDI-4DTE can be well applied to all-optical transistor and super-resolution fluorescence imaging.The stained micelles can be imaged to obtain the imaging resolution of 35.6 nm.(4)The difference of TDI-4DTE in rigid planar structures of their open and closed isomers which lead to the difference of them in solubility.The intermolecular π-π stacking interaction can be modulated by the photochromic DTE units in the molecule,resulting in macroscopic precipitation-dissolution phenomena visible to the naked eye and microscopic nano-structure changes,accompanied by fluorescence output.Upon 302 nm UV irradiation,significant precipitation can be observed within a few seconds,and then upon 621 nm visible light irradiation,the precipitation gradually dissolves within half an hour.By changing the 302 nm UV irradiation intensity,different microscopic morphology of the precipitate,including nanoparticles,nanofibers and nanosheets,has been observed,indicating the dynamic control process of self-assembly.In addition,under ultraviolet light,TDI-4DTE is assembled into nano-sheets in the solid polymer film,and through fine ultraviolet light regulation,it is assembled into monomolecular thin film at the oil/water phase interface.This has deepened our understanding of controlled molecular self-assembly and provided a new method for self-assembly of monomolecular membranes in molecular electronics.(5)In order to further regulate the near-infrared emission of TDI,get rid of the dependence of ultraviolet light,and improve the solid-state luminescence performance of fluorescent molecular switches.On the basis of the previous work,a visible light sensitive solid near-infrared star triad,TDI-4(DTE-TPE),four TPE-DTE groups covalently coupled with one TDI near-infrared fluorophore through O-bridged has been designed and synthesized.TPE molecule not only extends the conjugation of DTE as the electron donor group,but also acts as the large steric hindrance AIE-active group to achieve the highly distorted three-dimensional structure of TDI-4(DTE-TPE).Upon 405 nm visible light irradiation,TDI-4(DTE-TPE)exhibits obvious photochromic behavior,and its fluorescence quenching is over 90%,with good reversibility and fatigue resistance.TDI-4(DTE-TPE)shows aggregation-induced emission enhancement(AIEE)property in dichloromethane/hexane binary solvent systems.The solid film of TDI-4(DTE-TPE)has a near infrared fluorescence emission with the maximum emission wavelength of 786 nm,and the fluorescence intensity is 35 times higher than that of TDI powder.Upon the alternative irradiation of 405 nm and 561 nm laser,the all-visible-light super-resolution fluorescence imaging with a resolution of 30 nm has been realized.