【作者】 袁春雪；

【导师】 陶绪堂；

【作者基本信息】 山东大学 ， 材料学， 2009， 博士

【摘要】 有机发光材料由于其在有机电致发光器件、有机激光器、太阳能电池及光学传感器等诸多领域的应用前景而一直是材料领域的一个研究热点。然而绝大多数的有机发光材料存在聚集态荧光淬灭(aggregation-caused quenching,ACQ)效应,即在稀溶液中有较强的荧光发射,但在薄膜或晶体等聚集态时由于形成了诸如π-π密堆积、H-聚集体或是激基复合物等,而表现出弱的荧光。这种“聚集态荧光淬灭效应”大大限制了光电器件的发展,因为这些应用绝大多数都要求有机发光材料的使用是在固态下。从这种意义上来说,研究和探索高效荧光材料,特别是在固态下的强荧光材料具有重要的理论和实践意义。近年来,一种非常规的聚集态荧光增强(aggregation-induced emission,AIE)现象受到了研究者的广泛关注。与传统的荧光材料的发光性质完全相反,它们在溶液状态下几乎没有荧光,但在聚集状态下却有很强的荧光,很好地解决了传统染料严重的固态荧光淬灭效应,在OLED等光电领域具有很好的应用前景。Tr(o｜¨)ger’sBase(TB)具有特殊的刚性Λ-型扭转构型,理论上讲,其空间位阻作用在分子堆积时不利于形成π-π密堆积,可以有效地改善由于π-π密堆积所引起的有机发光材料常见的固态荧光淬灭现象。而有机吡啶盐由于其优良的化学和热学性能在光电领域备受瞩目。基于这两方面,本论文从分子设计的角度出发,选择Λ-型的TB骨架作为分子的基本框架,将具有多功能性质的吡啶盐引入其中,开发了一类新的具有聚集态荧光增强现象的Λ-型吡啶盐类发光材料,并详细地研究了它们的光物理性质和结构与性能之间的关系,初步探索了其在生物探针领域的应用。这些TB类化合物的合成路线比较简单,主要通过脑文格反应和离子交换反应,无需柱层析提纯,且产率较高。我们通过核磁共振谱、元素分析等手段对其进行了结构表征与鉴定。晶体是物质存在的最基本形态,了解晶体中分子结构和分子的堆积形态,对于研究物质结构与性能之间的关系具有重要的指导意义。本论文利用挥发法和扩散法成功生长了五个TB类化合物TB1、TB2、DMDPS、DMDPN与DMDP-Hg和一个平面型吡啶盐化合物DPPS的单晶,并通过单晶X射线衍射技术解析了它们的晶体结构,从晶体工程学的角度出发,讨论了它们在凝聚态下的分子形态、堆积方式以及分子间相互作用力等因素与光学性质之间的关系。晶体结构分析表明,我们合成的TB类化合物分子堆积时均未形成π-π密堆积,验证了我们分子设计理论的正确性。对于有机-无机复合的吡啶盐化合物DMDP-Hg,无机的阴离子通过S…S相互作用形成了一维链,贯穿于有机的阳离子通过C-H…π相互作用组成的二维网状结构中,形成了三维空间的网络互穿结构,显示了其在超分子化学领域的研究价值。为了探索这类化合物特殊AIE性质的起因,了解结构与性质之间的关系,我们合成了平面型的吡啶盐化合物DPPS,与Λ-型吡啶盐DMDPS截然相反,DPPS具有经典的固态荧光淬灭现象。通过比较研究DMDPS和平面型的吡啶盐DPPS的发光性质和晶体结构的不同,我们认为这类Λ-型吡啶盐类化合物特殊的聚集态荧光增强主要归因于其特殊的Λ-型的分子构型。在Λ-型DMDPS的晶体结构中,相邻两个分子间的距离为3.8(?),远远大于经典的π-π密堆积间距3.3(?),而平面型的DPPS分子间距离只有3.3(?)。溶液中TB类化合物的对映异构化以及分子的振动动态过程耗散了能量,打开了非辐射跃迁的通道,致使没有荧光发射。而固态下,贡献于特殊的Λ-型的较大的分子间距离导致的分子间相互作用的淬灭以及动态过程的抑制和较好的分子内电荷转移致使染料分子表现出了强的荧光。这类化合物是离子型化合物,具有较好的水溶性,我们可以使用喷墨打印的方式制膜,绿色环保,它们在有机电致发光器件领域有较好的应用前景。蛋白质荧光探针尤其是turn-on探针定性和定量分析蛋白质由于其高的灵敏度、低的背景噪音以及它们在化学、材料、生物和医药领域潜在的应用前景而备受关注。我们设计合成的这一类水溶性Λ-型吡啶盐类化合物DMDPS、DMDPI和DMDPN具有优良的光物理性质(吸收在390-400 nm,发射峰在545 nm,较大的斯托克位移150 nm左右,可以避开蛋白质分子自身的吸收和内源荧光的影响)和特殊的聚集态荧光增强性质。基于此,本文详细研究了它们与蛋白质的相互作用,建立了以DMDPS、DMDPI和DMDPN为探针,荧光光谱法实现对蛋白质的定性和定量分析。它们在溶液状态下没有荧光,但在含0.05 w/v SDS的PBS缓冲溶液中,它们通过疏水作用、静电作用等非共价键作用结合到蛋白质分子上,形成聚集体,发射出较强的荧光,因此它们可以作为蛋白质荧光turn-on探针。更重要的是,在低的蛋白质BSA浓度范围(0-70μg/mL),它们的荧光峰值与BSA的浓度成非常好的线性关系,因此它们还可以用于蛋白质的定量检测。另外,特殊的AIE发光性质使我们可以用高的染料浓度进行痕量蛋白质的检测。总之,在探索高效荧光材料的过程中,本论文提出了一种新的固态强荧光材料的设计思路,开发了一个新体系的聚集态荧光增强材料,并通过研究化合物的晶体结构和对比实验,对此特殊的发光性质做出了合理的理论分析与解释。另外,我们将这类水溶性的化合物应用到生物探针领域,用于蛋白质的识别与定量检测,取得了令人满意的结果。鉴于它们独特的结构特征和优异的发光性能,具有较高的理论研究价值和潜在的应用前景。更多还原

【Abstract】 Organic optoelectronic materials have been studied extensively for their important applications in organic light-emiting diodes（OLEDs）,organic laser diode,organic solar cells,chemical sensors,and so on.However,most organic chromophores are highly emissive in solution but become weakly luminescent in the solid state,which was called aggregation-caused quenching（ACQ）.It is mainly attributed to the formation of theπ-πclose stacking,excimer,and H-aggregation.Aggregation quenching has been the thomiest problem in the development of optoelectronic devices because the luminescent materials are predominately used as thin solid films.In this sense,studying and searching of excellent optical materials,especially those strongly emissive in the solid state,would be of great importance in both theory and practice.Rencently,an unusual optical phenomenon,namely aggregation-induced emission （ALE）,has attracted much attention.Opposite to traditional ACQ materials,they are nonemissive in solution but highly luminescent in the solid state.The discovery of AIE-active materials resolves primarily the problem of fluorescence quenching resulted from the aggregation.And they have shown potential applications in optoelectronic fields such as OLEDs.A-shaped geometry configuration of Tr（o|¨）ger’s base is theoretically disadvantageous to formπ-πclose stacking,which commonly results in fluorescence quenching in the solid state.Organic pyridinium salts are historically of special interest in photoelectric field due to their good chemical and thermal properties. Considering these two aspects,we developed a number of A-shaped pyridinium salts based on Tr（o|¨）ger’s Base which exhibit a typical AIE behavior.In this paper,we studied their photophysical properties and the relationship between structure and properties in detail.Meanwhile,we also explored their application in bioprobes field.The synthetic routes and purification of these TB analogues are simple,mainly according to the Knoevenagel E and ion-exchange reaction and without column chromatography.These compounds were characterized and confirmed by ¹H NMR,¹³C NMR,and elemental analysis methods.Crystal structure is very important for the study of the relationship between the structure and properties.Five new TB analogues（TB1, TB2,DMDPS,DMDPN,and DMDP-Hg） crystals and one planar pyridinium salt DPPS crystal were obtained by evaporation and diffusion methods,and these crystal structures were investigated by X-ray diffraction.The molecular conformation, molecule stacking and intermolecular interactions in the aggregation state were investigated in detail.It is found that all of these five TB analogues doesn’t formπ-πclose stacking,which proved our molecular design theory.For organic-inorganic hybrids DMDP-Hg,it comprises a three-dimensional supramolecular network constructed from one-dimensional Hg（SCN）⁴ anionic chains,which only constructed by the building block Hg（SCN）^4- linked via S…S interaction and two-dimensional cationic layers.To explore the reason of AIE phenomenon of DMDPS and study the relationship between structure and properties,a planar pyridinium salt DPPS was designed and synthesized as a contrast.Different from DMDPS,DPPS has a planar conformation and shows normal optical properties.It exhibits efficient fluorescence in solution and weak emission in the solid state.Compared the optical properties and structures of DMDPS and DPPS,we speculate that the enhanced emission of DMDPS may mainly be attributed to the twisted geometry configuration which sterically disturbs close packing by increasing intermolecular distances.The distances between two neighboring molecules of DMDPS and DPPS are found to be approximately 3.8（?） and 3.3（?）, respectively.The enantiomerization and/or intramolecular vibrational motion which induced the nonradiative deactivation process caused fluorescence quenching in solution while loose stacking resulted from twisted molecular geometry configuration possibly reduced the distance-dependent intermolecular quenching effect,restrict of dynamic processes,and effective intramolecular charge-transporting to produce intense fluorescence in the aggregation state.Fluorescence（FL） bioprobes especially the turn-on bioprobes for protein detection and quantification have received great attention due to their high sensitivity,low background noises,and accordingly,they show potential applications in chemistry, materials science,biology and medicine.Water-soluble A-shaped pyridinium salts DMDPS,DMDPI,and DMDPN,which possess AIE phenomenon and excellent photophysical properties,such as the absorption in the near-UV region(λ_max≈400 nm) and the large Stokes’ shift（△λ≈147 nm）,can be used as fluorescence turn-on bioprobes for protein detection.Further more,the plots of photoluminescence intensity versus BSA concentration（0-70μg/mL） display a good linear relationship,indicating quantitative detection can be achieved.Moreover,the AIE nature allows the use of large fluorophore/protein ratios,enabling the detection of trace amounts of proteins.In summary,in the process of the exploration of highly emissive organic solids,we presented a new design strategy and established a new system of AIE materials. Meanwhile,we gave reasonable explanation of the AIE phenomenon of the A-shaped pyridinium salts by analyzing the crystal structures and through comparative experiments.In addition,the water-soluble A-shaped pyridinium salts were used in bioprobes field and the results are satisfactory.In view of their special structural feature and excellent optical properties,A-shaped pyfidinium salts are good candidates for theoretical research and with potential applications.更多还原