Design, Synthesis And Photoelectric Properties Of Cyano Substitute Distyrytbenzene Derivative

Over recent years, π-Conjugated organic luminophores have aroused tremendousinterests in the field of organic optoelectronics. On account of their uniquephotophysical properties, superior thermal stability, structural diversity and readilyobtained. They have been widely used in the fabrications of organic light emittingdiodes (OLED), organic solar cells, field effect transistor and chemosensors. cyanosubstitute distyrylbenzene and its derivatives are typical light-active π-conjugatedmolecule systems. These materials have alternate double bond and benzene ring. Thesp2hybridization structure of carbon atom on the double bond andπ-electron systemon the benzene ring made the molecule became a good π-conjugated skeleton owingto their delocalization electronic structure. The introduce of cyano group on themolecule increasing the molecular electronic affinity and reducing the barrierpotential of electron injection. That is benefit to balance the injection and transport ofcharge carriers. While the introduction of the cyano group made the molecule easy toform a variety of intermolecular hydrogen bond interactions, imparting goodcrystallinity to the material. So, it is easily to analyze the relationship betweenoptoelectronic properties and molecular structure or stacking methods by determinethe crystal structure. Furthermore, there is a large number of substitution sites on themolecule, it will make materials have a wider range of applications throughreasonable introducing functional substituents. Using cyano-substituted distyrylbenzene (-CNDSB) as the central core fourcompounds were synthesized by substituted with different electron-donating abilitysubstituents of carbazole, diphenylamine, indole derivatives and phenothiazine groupon the both ends of the molecule. Combine with cyclic voltammetry test, the influenceof molecular photophysical properties by different electron-donating abilitysubstituents was studied. From carbazole, diphenylamine, indole derivatives tophenothiazine the oxidation potential gradually decreased，indicating the increase ofthe electron-donating ability. The fluorescence and UV absorption spectra of thecompounds (except the molecule substituted by phenothiazine) gradually shifttowards the longer wavelengths with the increase of the substituents electron-donatingability. The introduction of electron-donating substituent groups both increase theHOMO level and LUMO level of molecules, but bigger improved the HOMO level.Finally, the bandgap of the molecule decreased. In addition to phenothiazinesubstituted compounds, other molecules have shown AIE and two-photon absorptionproperties. The electron-donating ability of phenothiazine is too strong, thedistribution of HOMO level and LUMO level of the molecule is complete separated.The strong intermolecular charge transfer reduce the luminous efficiency of themolecule. Therefore, it is better to choose substituents whose oxidation potential lessthan0.29V in the modification of-CNDSB. Even though the data we have got is notenough to elaborate the specific connection between the oxidation potential of thesubstituents and spectral changes of synthetic compounds, However, it can provide areference for the subsequent synthesis of the compound.Four compounds were synthesized by changing the position of the cyano groupon double bond and replace the peripheral benzene with different sites connectedthiophene. Experimental results show that cyano substitute on the β position of doublebond reduce the LUMO level of the molecule more effectively, but has little influenceon the HOMO level of the molecule. The molecule connected thiophene on the3position has a higher LOMO level and lower HOMO level than the molecule connected thiophene on the2position. So, the bandgap of molecule connectedthiophene on the3position is bigger. In addition, the influence of HOMOlevel(average difference of0.2eV) of different connected position of thiophene isgreater than that of the LOMO level (a difference of0.07eV). Cynao substitute ondifferent position of double bond led to different luminescence efficiency of themolecule in dilute solutions. The reason for this discrepancy is that the conformationof the molecule with cynao on position change from trans to cis-form more easily.The crystals of these compounds were growth by solution diffusion method.There were three crystals which was good enough to take single crystal x-raydiffraction. Ordered pore structure observed in the crystal of carbazole-substitutedcompound (CzCNDSB), and the diameter of the pore which is the result of twistedconfiguration and a variety of molecular interactions is0.8nm. The molecule showC-shaped configuration and form dimers in the crystal of DPACNDSB (moleculesubstituted with diphenylamine). This specific molecular structure is a result of sterichindrance and inter-molecular π-π interactions. cyano substitute distyrylbenzenederivatives can form many unique crystal structure so it has a great value in the studyof organic crystals.The piezochromic behavior of CzCNDSB was studied by anisotropic grindingand isotropic hydrostatic pressure. The results show that the reason for color changeof the grinding material is the transform from crystalline to amorphous state. And theenhanced intermolecular polarization result in the color change under differenthydrostatic pressure. It is worth to note that there was a good liner relationshipbetween emission wavelength and pressure intensity. Imply CzCNDSB is a goodpressure-sensing material.