【作者】 陈明；

【导师】 唐本忠； 秦安军； 孙景志；

【作者基本信息】 浙江大学 ， 高分子材料， 2015， 博士

【摘要】 聚集诱导发光(AIE)是唐本忠等人在2001年发现并定义的一个光物理领域的新概念,是指一类具有螺旋桨结构的共轭分子在溶液中不发光或只微弱发光,而在聚集状态下发光显著增强的现象。和传统的聚集促使荧光猝灭(ACQ)分子相比,AlE分子能够利用自身聚集发光,因此在有机发光二极管、传感和生物成像等领域有着广阔的应用前景。虽然目前被报道的A]E分子种类繁多,但它们大多数是基于多苯基噻咯和四苯基乙烯的衍生物。尽管如此,这些原型分子也存在着一些不容忽视的问题：例如,多苯基噻咯的制备过程繁琐,分离困难且对碱不稳定：四苯基乙烯内部含有碳碳双键,这将影响了分子作为材料使用的稳定性。因此,为克服这些不足,在本论文中我们制备了一类基于吡嗪的全芳环AIE体系,并探讨了这些分子结构与性能之间的关系。首先,我们开发了一类新型的AIE分子一四苯基吡嗪(TPP),并以其为原型设计、合成了一系列苯基或甲氧基修饰的聚集荧光增强(AEE)衍生物。TPP及其衍生物的制备过程简单且反应条件温和,因此适合大规模制备。TPP分子的螺旋桨结构使其在溶液态通过分子内转子旋转耗散激发态的能量,使得发光微弱,而在聚集态,这一构型有效阻止了分子间激基缔合物的形成,同时,分子间C-H…π氢键的存在刚化了分子的构型,促使了其辐射跃迁的发生,从而发光增,强。此外,也由于不含不稳定的碳碳双键及硅碳键,TPP及其衍生物具有良好的热、光及化学稳定性。而TPP中吸电子的吡嗪环的存在为设计、合成具有不同发射波长的衍生物提供了便利的平台。其次,基于TPP原型分子吸电子的特性,通过在分子中引入强给电子性能的三苯胺基团,使其发射波长发生明显的红移。在此基础上,讨论了分子结构对其光物理性能的影响：由于给受体单元的扭曲构型,给受体单元对数增加,分子内单元间电荷转移(ICT)效应起叠加效应,因此分子的摩尔吸收系数成接近线性倍数的增加；相反,给受体单元数的增加只会略增加分子的共轭,使其最大吸收波长略发生红移。也由于这些分子特殊的构型,使其的发光行为兼具有扭曲分子内电荷转移(TICT)和AEE效应,其中三苯胺ACQ单元数的增多和分子体积增加引起的刚性增大将会对分子的AEE效应产生明显的影响。另外,这类分子在不同极性溶剂中具有显著的溶致变色行为,且有选择的展现了优异的电致发光、双光子吸收以及自组装等性能。为进一步研究吡嗪类AlE分子的构效关系,以一价铜催化的叠氮-炔点击聚合制备了含2,3-二腈基-5,6-二苯基吡嗪(DCDPP)和TPP的聚三唑(PⅠ和PⅡ)。虽然DCDPP和TPP均具有AIE活性,但PⅠ和PⅡ却分别呈现ACQ与AIE的性能。为此,利用DCDPP和TPP在晶体中的堆积信息作为指导模型推断了造成这种发光性能差异的原因： PI中重复单元间存在比较强的C-H.··N氢键,因此增强了聚合物分子链间或链内的相互作用,迫使了基于吡嗪环和腈基平面强的π-π堆积效应的形成,从而很大程度上猝灭了聚合物聚集时的荧光。相比之下,P11分子链间或链内只可能存在较弱C-H…π氢键,且TPP单元螺旋桨状的结构使其在固态不能紧密堆积但足以限制苯环旋转,从而使激发态的能量更多以辐射跃迁的方式得以耗散。此外,PⅠ和PⅡ在溶液状态对银离子有着截然不同的荧光响应方式,其中,PⅡ与银离子作用后有更为显著的荧光增强行为,并且具有非常好的专一选择性。最后,利用铜催化叠氮-炔环加成(CuAAC)和钌催化叠氮。炔环加成(RuAAC)修饰吸电子性较强的DCDPP分别制备了具有TICT和AEE特性的1,4-立构和1,5-立构的异构体。与1,5-异构体相比,1,4-异构体中三唑环与DCDPP单元较小位阻效应决定了其较好的共轭,因此发光波长红移(二者分别发射浅蓝和深蓝光)。基于所得异构体强吸电子的特性,这两个分子均能够和强电子给体三苯胺在聚集状态下形成紧密的电荷转移复合物,呈现红光发射。更多还原

【Abstract】 Aggregation-induced emission (AIE) is a novel photo-physical phenomenon which was termed by Tang, et al. in 2001. It refers to a unique phenomenon that a series of propeller-shaped molecules are weakly or non-luminescent in their diluted solution, but greatly enhance their emissions in the aggregate state. Compared with traditional luminophores with aggregation-caused quenching (ACQ) effect, AIE luminogens (AIEgens) could enable aggregation to play positive roles in enhance of emission, thus possessing a huge application potential in the fields of organic light-emitting diodes (OLED), biological and chemical sensors, biological imaging and so on. Up to now, lots of AIEgens have been generated, but most of them are originated from archetypal phenyls substituted silole and tetraphenylethene (TPE). Nevertheless, the intrinsic disadvantages of these AIE cores should not be ignored:for example, phenyls substituted silole and its derivatives are troublesome in preparation, especially in their purification, and unstable under basic conditions; the double bonds in TPE and its derivatives worsen their stabilities under photo and heating. Thus, keeping above questions in mind, we developed a series of pyrazine-based AIE gens, and the relationship of structure-property of them was also investigated in detail.Firstly, we developed a new type of AIEgen of tetraphenylpyrazine (TPP) and its derivatives. It is worthy noting that the preparation of TPP-based AIEgens is feasible, making them applicable in diverse areas. The propeller structure of these luminogens makes them easy to disspitate the excited state energy via intramolecular rotation in solution, but greatly open up the radiative transition channel due to the intermolecular C-H…π hydrogen bond to stiffen molecular conformation in aggregate state, which is featured as AIE or aggregation-enhanced emission (AEE). Because no double bonds and Si-C bonds are involved, TPP has good thermo-, photo- and chemostabilities. Moreover, the electron-withdrawing property of TPP provides a facile platform to design derivative with colorful emissions from deep blue to pure blue.Secondly, taking advantage of the electron-withdrawing ability of TPP, we designed a series of molecules containing TPP and TPA units. The photophysical property investigation showed that the number of acceptor-donor pairs contributed more to the molar absorptivity but less to the maximum absorption wavelength. Also, these molecules exhibit both effects of twisted intramolecular charge transfer (TICT) and AEE in emission. Furthermore, they also display the unique properties of solvatochromism, and selective excellent performance of two-photon absorption, self-assembly and electroluminescence, etc.Thirdly, based on our previous results, polytriazoles PI and PII containing the AIEgens of 2,3-dicyano-5,6-diphenyl pyrazine (DCDPP) and TPP were facilely prepared by Cu(I)-catalyzed azide-alkyne click polymerization, respectively. Interestingly, PI and PII display a contrary photo-physical behaviors:the former suffers from the ACQ effect, whereas, the latter is AIE-active. As informed from the crystal packing of parent molecules and deduced:The intermolecular or intramolecular interaction of π-π stacking in PI could be formed based on the plane of dicyanopyrazine groups in repeating units, from which the light quenching species like excimers will probably be generated. Whereas, in PII, no such species could be generated, making it AEE-active according to the restriction of intramolecular rotation mechanism. Furthermore, these polytriazoles could be used to detect silver ions and more sensitive and selective effect was observed for PII.Finally,1,4- and 1,5-regioregular triazole derivatives containing DCDPP moieties were facilely prepared by Cu(I)-catalyzed azide-alkyne cycloaddition and Ru(II)-catalyzed azide-alkyne cycloaddition, respectively. The photophysical property investigation revealed that both isomers possess TICT and AEE effect. In addition, thanks to their electron-withdrawing ability, they could form charge transfer complexes with strong-electron donating molecule of triphenylamine in aggregate state and emit red light, which provides a new strategy to generate red-light emitting materials.更多还原