Design, Synthesis And Property Of Functional Fluorescence Materials Based On1,3,5-Triazine And1,3-butadiene Unit

In the past decades organic opto-electronic functional materials have drawn significant attention for their extensive applications in many areas such as organic/polymeric light-emitting diodes, photovoltaic cells, chemical and biological sensors, nonlinear optics, field-effect transistors etc. Much work has been focused on designing and synthesizing novel organic materials with excellent overall performance and also on exploring the relationship between their structure and properties.Recently,1,3,5-triazine derivatives have attracted great interest because of their high electron affinity, high thermal stability and perfect structural symmetry. Multibranched molecules containing1,3,5-triazine unit as a strong electron-acceptor exhibit excellent two photon absorption (TPA) properties with large TPA cross-section value. Buta-1,3-diene unit has been widely used as a functional block to build the conjugated molecular materials, which exhibit excellent opto-electronic properties. In this thesis, a series of conjugated molecules and polymers based on1,3,5-triazine unit or buta-1,3-diene unit have been designed and synthesized. Their photophysical properties have been studied, and the relationship of the structure and properties has also been primarily explored. In addition, theoretical calculation has been tried to explain some experimental phenomenon. The main contents and results are briefly described as following:Chapter1reviewed the general concept, principles of molecular design, recent progress and potential application of organic two-photon absorption, organic light-emitting diodes and aggregation induced emission enhancement materials. Then, the design strategies and main contents of this thesis were outlined.In chapter2, four new1,3,5-triazine-based molecules (Ⅰ-1-Ⅰ-4) containing dietheylamine group at6-position of triazine unit were designed and synthesized via Suzuki coupling reaction and Sonogashira coupling reaction, in which the triazine acted as a strong electron-accepting center connecting with some electron-donating group through the conjugation bridge of thiophene ethynyl or phenyl group. Their structures were characterized by1H-NMR,13C-NMR, MS and EA. Their photophysical and electrochemical properties were studied. It was found that their UV-vis absorption exhibited little change as the polarity of the solvent increases, but their emission showed significant positive solvatochromic effect, which was possibly originated from the intramolecular charge transfer process. Meanwhile, the influence of trifluroacetic acid (TFA) and some metal ions on their UV-vis absorption and emission spectra were detailed studied. The λmax of absorption and emission for the compound1-1exhibited obvious hypsochromic shift with the increment of the concentration of TFA or Hg2+ion due to the weakened intramolecular charge transfer. On the contrary, the λmax of absorption for the compound I-2-I-4showed bathochromic shift with the quench of the fluorescence due to the enhaced intramolecular charge transfer induced by the TFA or Hg2+ion. In addition, the photophsysical properties of Ⅰ-1-Ⅰ-4was also sensitive to the addition of Cu2+ion, which dramtically changes the UV-vis absorption and emission spectra much different from TFA and Hg2+ion. Two-photon absorption properties of the compounds in THF were measured by two-photon induced fluorescence (TPIF) measurement technique with the laser wavelengths between710～990nm. The results indicated that the electron-donor’s strength and the π-conjugation extension have great influence on the TPA cross-section value (σ2).In chapter3, three new molecules (Ⅱ-1-Ⅱ-3) with N,N-bis(2-hydroxyethyl)amino group on1,3,5-triazine unit were synthesized and characterized. And then two water-soluble1,3,5-triazine-based molecules (Ⅲ-1-Ⅲ-2) were obtained with two PEG chains connecting the hydroxyl groups of Ⅱ-2-Ⅱ-3, which was further confirmed by GPC measurement. UV-vis absorption and emission spectra measurements indicated these compounds showed similar photophysical properties to the compounds (Ⅰ-1-Ⅰ-3) due to the existence of the intramolecular charge transfer state. Compared to Ⅰ-1-Ⅰ-3, the electron-accepting inductive effect of two-end hydroxyl group in Ⅱ-2-Ⅱ-3induced the fluorescence emission bathochromic shift in all solvents measured. The influence of TFA, Hg2+and Cu2+ions on their UV-vis absorption and emission just resembled to compounds (Ⅰ-1-Ⅰ-3). Two-photon absorption studies indicated that the hydroxyl group exerted little influence on the TPA cross-section value (σ2). The water-soluble molecule (Ⅲ-1-Ⅲ-2) showed quite similar photophysical to compounds (Ⅱ-2-Ⅱ-3).In chapter4, four triazine derivatives (Ⅳ-1-Ⅳ-4) with azacrown ether groups at6position of triazine unit, as well as triphenylamine as the donor were designed and synthesized via Suzuki reaction and Sonogashira reaction. Their structures were characterized by1H-NMR,13C-NMR, MS and EA. It was found that the introduction of the carbon-carbon triple bond in Ⅳ-3and Ⅳ-4induced the red shift of their fluorescence emission in polar solvents and also enhanced the TPA cross-section value (a2) due to the extending the molecular conjugation. The UV-vis absorption for all the compounds showed obvious bathochromic shift with the quench of the fluorescence by adding the TFA to their CH3CN solution. The response toward some different metal ions was investigated. It was found that Cu2+, Hg2+, Pb2+as well as Ba2+ion can influence the their UV-vis absorption and emission. The experimental results combining the theoretical calculation indicated that there were two different mechanisms for the coordination of metal ions to the corresponding compounds, which possibly originated from the coordination of the metal ions with the azacrown ether or the N atom in triazine unit, respectively.In chapter5, five new linear conjugated polymers (P1-P5) were synthesized via Suzuki coupling of (Z, Z)-1,4-dibromo-1,4-diaryl-buta-1,3-diene with aromatic diborates. Their structures were characterized by1H-NMR,13C-NMR, FT-IR, GPC and TGA. All the polymers showed high thermal stability and good solubility. It was found that the absorption and emission of the polymers could be adjusted through changing the side aromatic group, and the partial twisted structure of two aromatic groups at the end carbon of buta-1,3-diene unit could hinder the interchain interaction of conjugated main chain and improve the photophysical properties of the polymers in the solid state. The electrochemical and electroluminescent properties of the polymers were primarily studied. The device based on P3showed the best result among P1-P5. The luminance maximum is520cd/m2, and current efficiency maximum is0.27cd/A.In chapter6, a series of new1,3-diene-based molecules (V-1-V-7) with different aromatic groups at the end of1,3-diene were synthesized and characterized. TGA measurement indicated that all the molecules showed high thermal stability. Their photophysical properties in the solution and in the thin film state were studied, and the aggregation induced emission enhancement (AIEE) was investigated in the solution of THF/H2O system as well as at different temperature in THF. All the molecules showed bright blue or green emission in THF solution. Compared with the solution, compound V-3and V-4exhibited an obvious hypsochromic shift in the thin film. In a water/THF mixture, all the compounds except V-3and V-5became more emissive due to the aggregate formation. The emission was also enhanced and hypsochromic shifted by decreasing temperature of the THF solution. The result suggested that the AIEE effects of the compounds were caused by the restriction of intramolecular rotation of the large steric aromatic groups at the end of1,3-diene unit, which had a great influence on their AIEE activity.