Synthesis And Study Of Of Novel Cyano-substituted Orgnic Fluorescent Molecules With Triphenylamine Donor

Triphenylamine and its derivatives are provided with high electron donating ability and modification, which have been widely applied in the field of electric-charge transport materials, electroluminescent materials and molecular probes etc. Cyano group(-CN) as the well-known strong electron acceptor has been widely used for red-light chromophores, which could promote the process of intramolecular charge transferring so as to tune the optical properties. Optical properties of the molecules with electron accepting and donating units could be easily tuned via controlling the extent of intramolecular charge transfer(ICT). Based on what I have mentioned above, a series of triphenylamine fluorescent molecules with multiple electron-withdrawing cyano substituents was designed and synthesized, systematically studied the different number of electron withdrawing cyano substituent effect on intramolecular charge transfer, and further studied the thermal stability and optical properties of these molecules. Electrochemical properties and Density Functional Theory calculations were used to further verify the tune of cyano substituents to the electronic level. In addition, the cyano-substituted chromophores had obvious optical response to metal ions. Especially, with the addition of Hg2+ ion, the blue shift of absorption spectra and the decrease of emission intensity suggested that the compounds have potential applications in high selectivity and sensitivity of the optical sensor.The main contents of this thesis are as the following parts:1、The p-xylene and single acyl triphenylamine as the starting material, D-π-A-π-D type fluorescent molecules were synthesized through bromination and witting reaction of, then diacyl triphenylamine derivatives were prepared by reaction with Vilsmeier-Haack reagent(DMF and POCl3), further the 3-5 molecules of cyano-substituted red-light chromophores based triphenylamine donor were synthesized by Knoevenagel condensation reaction with malononitrile. Relevant features were characterized through XRD, TGA and DSC. All of them were present excellent thermal stability, especially the decomposition temperature could improve about 40°C with the introduction of mutil-cycno, which could expand the scope of its application. We found that compounds 3-5 had a certain crystallinity and exhibit the crystallization tendency in solid state due to the end of cyano substituted. Using UV-Vis absorption spectra and FL emission to test their optical properties,the results showed that the cyano substituents of conjugated system could largely increase the intramolecular charge transfer, thus it could obviously tune its optical properties. The maximum absorption and emission spectrum of compounds 3-5 in the film and solid state had a significantly red shifted compared with solution due to strong molecular interactions or π–π* aggregation. Compared to the compounds 3 and 5, compound 4 with multi cyano substituted showed obvious red shift, moderate fluorescence lifetime and high fluorescence quantum yield. The compounds 3-5 showed an excellent solvatochromism property. When increasing solvent polarity, the solvation effect had a great influence on the fluorescence emission and Stokes shift, and the peak appeared red shift of 40 nm, exhibit good solvent relaxation phenomena.Electrochemical properties showed that the different cyano substituents could tune the HOMO and LUMO levels. In addition, the notable optical response of metal ions for the cyano-substituted chromophores was investigated. Especially, with the addition of Hg2+ ion, the absorption spectra showed the blue shift, and the emission intensity decreased, especially a new peak appeared at around 330 nm, that suggested the new metal complexes possibly formed between the cyano substituents and metal ions or metal ion-induced optical quenching happened. In addition, Density Functional Theory calculations were used to further understand the effect of the cyano substituents on the photoelectron properties of the donor-acceptor molecules.2、Two novel compounds 3 and 5 with D-π-A type triphenylamine fluorescent molecules were synthesized by Suzuki coupling reaction. Using UV-vis and FL to test their optical performance, the maximum absorption wavelength of compounds 3 and 5 in dichloromethane solution was in the range of 399 nm-404 nm, the maximum emission wavelength at 472 nm-496 nm, in the film the maximum emission wavelength was in the range of 503 nm-538 nm, the maximum emission wavelength at 532 nm-546 nm in solid state. Compared to compound 3, maximum absorption wavelength and the maximum emission wavelength of compound 5 showed obvious red shift with a strong yellow-green fluorescence emission in dichloromethane. The results showed that cyano had obvious adjustment. Compared with in solution, the absorption and emission peaks showed red shift in film and solid state due to the molecular aggregation effect. The absorption peak and emission peak of the compounds 3 and 5 showed obvious red shift with the solvent polarity increasing. In summary, the target compounds own excellent optical properties.