【作者】 赵鑫；

【导师】 卢然；

【作者基本信息】 吉林大学 ， 有机化学， 2014， 博士

【摘要】 以有机π-共轭分子构筑的有机光电功能材料在非线性光学、有机发光二极管、太阳能电池、离子与分子识别、光致变色等领域表现出巨大的潜在应用价值。在光物理性质方面，因各个研究领域对化合物的发光行为要求不同，有机π-共轭分子的荧光调控研究对于其光电功能的实际应用具有重大意义。在分子结构设计方面，树枝状分子因其结构的特殊性，表现出许多优异的光电特性，尤其在双光子吸收性质方面，其各个分枝之间的协作增强效应，可极大地增强化合物的双光子吸收能力；而棒状小分子由于其结构极其简单，化学合成步骤简便，经微小的结构修饰即可获得性质迥异的光电材料。本论文从有机π-共轭分子的树枝状与棒状构型为出发点，以化合物的荧光调控为目标，合成了一系列树枝状与棒状且荧光可调控的有机π-共轭分子，研究了其光物理性质，并取得了如下创新性研究结果：(1)利用Heck偶联反应合成了一系列具有枝化结构的基于苯并噻二唑核心的共轭化合物，并研究了其光物理性质。研究结果表明，无论是以三苯胺或是吩噻嗪单元作为枝化端基的电子给体，化合物均表现出强的光捕获能力。在溶剂依赖的光谱测试中，发现分子中存在着分子内电荷转移过程。在400nm波长光的激发下，T1、T2、TP2和P2的甲苯溶液均可发射出600nm左右的红色荧光，且当改变溶剂极性时，发射峰位随极性增大而红移。在820nm飞秒激光的激发下，可以观测到双光子诱导的红色荧光。非枝化结构的T1的双光子吸收截面为253GM，而枝化结构的化合物T2、TP2和P2的双光子吸收截面为594GM、351GM和517GM。因此，延长的共轭体系、枝化结构均有助于增强双光子吸收能力。(2)合成了一系列以三苯胺单元为核心、以具有不同给受体能力的吩噻嗪单元为外围基团的星形化合物P1、P2、PF、PC与PM。在合成过程中，化合物P1、P2的合成使用的是由外向内的“收敛法”，而PF、PC与PM的合成是使用的“发散法”。光物理性质的研究结果表明，通过引入不同的给受体单元，对结构进行电子给受能力的改变，可以调控化合物的荧光行为。在甲苯溶液中，其峰位分别为481nm、509nm、489nm、519nm与636nm，荧光颜色的改变从蓝光、绿光到红光。电化学测试表明，所有化合物因含有给电子的吩噻嗪基团均表现出较高的HOMO能级，而具有电子受体修饰的化合物PF与PM均表现出较低的LUMO能级。总之，通过对星形π-共轭化合物的电子给受体能力的调节，我们实现了荧光调控的目标。我们期待此系列化合物在双光子材料领域得到应用。(3)合成了含有三苯胺单元的氰基苯乙烯类D-π-A共轭化合物G1、G1-N和G2。通过调节共轭结构与吸电子能力，实现了发射绿色、橙色与红色荧光的固态发光体。该系列化合物虽然在溶液状态表现出较弱的发光，然而其在固态下均表现出较强的荧光发射。例如，化合物G2固体粉末的荧光量子产率为0.67，为其溶液状态荧光量子产率的20倍之多。X-射线单晶衍射数据表明分子间的氢键(C-H···O、C-H···N与C-H···π)共同作用使得分子的刚性增大，抑制了分子内的自由旋转发生，导致化合物固态下较高的荧光量子产率。因此，我们所设计的绿色、橙色、红色固态发光体有望作为OLED材料得到应用。(4)合成了含苯并咪唑单元的多芳基乙烯化合物BzIm-TPAN与BzIm-TPE。研究表明，测试中化合物在四氢呋喃稀溶液中的荧光量子产率值（以硫酸喹咛为参比）极低，分别为0.002与0.004；化合物在薄膜状态下，荧光量子产率（积分球方法）分别为0.27与0.99，该值与溶液态相比分别增强了135倍与247倍，其发射波长分别为532nm与492nm，可见，与不含氰基的BzIm-TPE相比，含有氰基单元的BzIm-TPAN的发射波长红移了40nm。上述聚集诱导荧光增强现象以及分子结构与荧光性质间关系的讨论为设计固态多色发光体提供了新思路。更多还原

【Abstract】 Organic optoelectronic materials constructed by π-conjugated molecules haveshown great potentials in nonlinear optics, organic light-emitting diodes, solar cells,molecule/ion recognition, photochromic and other fields. In the aspects ofphotophysical properties, since the demands of fluorescence in various fields aredifferent, the fluorescent modulation studies on π-conjugated organic molecules are ofgreat importance for their optoelectric applications. In the aspects of molecularstructures, branched/dendritic molecules, due to their particular molecularconstructions, possess many excellent optoelectric characteristics, for example, thecooperative enhancement of two-photon absorption in multi-branched structures;rod-like small molecules are easy to synthesize and modify, and usually minormodifications result in molecules with various optoelectric properties.Herein, we, on the basic concept of branched/dendritic and rod-like moleculesand towards the goals of fluorescence modulation, synthesized a series ofbranched/dendritic and rod-like π-conjugated molecules with controllablefluorescence and studied their photophysical properties. The innovative researchresults are as follows:(1) A series of branched molecules based on benzothiadiazole have beensynthesized by Heck reactions. It was found that the structrues with triphenylamineand/or phenothiazine as terminal groups have shown strong light harvesting ability.Intramolecular charge trasfer (ICT) was identified in the solvent-dependent tests.Compounds T1, T2, TP2and P2in toluene could emit red fluorescence at600nmexcited with400nm, and the emission redshifted with increasing solvent polarity.Excited with femtosecond laser at820nm, all compounds could give red fluorescence due to two-photon absorption. Non-dendritic structure T1has a two-photonabsorption cross section of253GM and branched structures T2, TP2and P2showtwo-photon absorption cross sections of594GM,351GM and517GM, respectively.Therefore, it can be concluded that extended conjugated system and branchedstructures may help increase the two-photon absorption cross section.(2) A series of triphenylamine cored, different phenothiazine groups basedstar-shaped molecules P1, P2, PF, PC and PM were synthesized according to“divergence” or “convergence” strategy. The photophysical results suggest that byintroducing different kinds of electron donor/acceptor, fluorescence behavior ofcompounds could be modulated. In toluene solutions, fluorescence peaks at481nm,509nm,489nm,519nm and636nm were observed, respectively, and the coloraltered from blue, green to red. Electrochemical tests showed that all compounds havehigh HOMO energy level, and PF and PM containing acceptors have low LUMOenergy level. The introductions of different electron donor/acceptor groups helpmodulate the fluorescence emission. The five compounds are expected to showapplications in two-photon absorption materials.(3) D-π-A conjugated triphenylamine substituted cyanostyrene derivatives G1,G1-N and G2were synthesized. These solid state emitters covering green, orange andred fluorescence were achieved by extending π-conjugation structure and introducingstronger electron acceptor. This series of compounds showed weak fluorescence insolution but strong fluorescence emission in solid state. For example, the fluorescencequantum yield of G2in solid reached0.67, about20times as much as that in solution.Single crystal X-ray diffraction data showed that intermolecular hydrogen bonds(C-H··· O, C-H··· N and C-H··· π) interactions increase rigidity of the molecule,restrict the intramolecular rotation and result in high fluorescence quantum yield insolid state. Therefore, we believed that these green, orange, red solid lumigens weregood candidates for OLED materials.(4) Two compounds (BzIm-TPAN and BzIm-TPE) containing benzimidazole, and cyano-triphenylethene or tetraphenylethene were synthesized. It was found thatboth compounds showed weak fluorescence in solution with quantum yields0.002and0.004. However, these values for thin film state were0.27and0.99, which were135and247times as much as those in solution, respectively. Cyano substitutedBzIm-TPAN emitted fluorescence with peak at532nm, showing a redshift of40nmcompared to phenyl compound BzIm-TPE (492nm). The emission properties in thinfilm provided a new design strategy for aggregation-induced emission materials.更多还原