【作者】 王延风；

【导师】 李希友； 翁羽翔；

【作者基本信息】 山东大学 ， 无机化学， 2009， 博士

【摘要】 苝二酰亚胺（Perylene tetracarboxylic acid diimide,简称PDI）类衍生物具有优异的热和光化学稳定性,对可见区到红外区的光有很强的吸收。是一种具有独特的光物理和光化学性质的有机光电材料。在太阳能转化、电致发光、以及生物荧光探针等领域有广泛的应用前景。近年来,对其光物理性质的研究愈来愈受到关注,并逐渐成为研究的热点。为了满足PDI化合物在不同领域的应用,通过对其结构进行化学修饰,以控制苝二酰亚胺类化合物的性质,是获得具有新颖的光电性质的PDI新材料重要手段之一。怎样去寻找一个有着新颖性质的结构一直是困扰人们的难题,本论文主要就这种有着优异性能的苝二酰亚胺类化合物的研究来寻找结构和性能间的联系,并尝试设计合成了一些具有特殊性质的苝二酰亚胺化合物并对其性质进行了深入的研究。我们的工作主要集中在以下几个方面:1.一种双亲性的苝二酰亚胺衍生物的合成和表征苝二酰亚胺（PDIs）中由于酰亚胺基团强的吸电子效应,它具有高的电子亲和式,这就使得它有可能成为一种很好的n-型有机半导体材料。科学家们通过在它的酰亚胺氮原子上引入了不同的基团,可以改变PDIs在固体时候的堆积,进而改善其半导体的性质。在PDIs的湾位引入像CN-这种吸电子基团能够非常明显的提高其作为n-型半导体的性能。我们设计合成了一种新型的PDI化合物,在湾位用酚氧基基团取代,一端的酰亚胺氮原子上则用疏水型的烷氧链取代。更加有趣的是,两个这样的PDI环用亲水型的三嗪环连在一起,形成具有非常好的双亲型的双层二聚体结构。这个化合物可以用Langmuir-Blodgett（LB）膜技术进行组装,形成高度有序的固体膜,以这种固体膜为半导体层的有机场效应晶体管（OFETs）具有很好的性质,其迁移率能够达到0.05 cm² V^-1 s^-1,开关比也能够达到10³,这种性质要远远好于用相应的PDI单体形成的LB膜。我们的研究结果表明,在膜形成前通过共价键将有机分子组装成有序结构是提高OFET能力的一种有效方法。2一种新颖的PDI三聚体中能量传递的研究绿色植物光合作用的原初过程中包括多步快速的能量传递和电子转移。在某种意义上说,自然界的光合作用反应中心是一种分子水平上的高效率的光伏器件。因此人工模拟生物光合作用中心的光致电子转移和能量传递对太阳能的光电转换和收集具有重要的理论指导意义。苝二酰亚胺衍生物具有极高的荧光量子产率和很好的光热稳定性,是模拟光合作用的理想分子。我们以三聚氰胺分子为中心,连接三个苝二酰亚胺单体分子,从而合成了共价连接的苝二酰亚胺三聚体。通过分子结构模拟、吸收光谱和核磁共振光谱可知其中的两个苝二酰亚胺单体呈面对面的空间构型,能够形成二聚体,而另一个苝二酰亚胺分子则以单体形式存在。荧光光谱实验揭示三体中单体的荧光被淬灭,这种现象说明该三聚体分子和LH2一样,有可能存在由单体到二聚体的光激发能的传递过程。飞秒时间分辨瞬态吸收光谱证实了苝二酰亚胺三聚体分子中单体向二聚体有传能过程。在稳态吸收光谱的基础上提出了单体和二体的共激发模型,并在该模型的基础上通过对时间分辨瞬态吸收光谱进行奇异值分解获取中间体组分信息,并进一步进行全局参量光谱和动力学拟合,获得了激发态光谱及衰减动力学,从而确定了单体向二聚体传能的途径。这个发现对于设计和构建新型的人工光采集体系具有重要的作用。3 Marcus界面电荷重排能用二氧化钛纳米粒子的粒径以及亲水性的关系染料敏化TiO₂纳米晶太阳能电池是一种接近实用的高效光电转化器件,进一步提高染料敏化太阳能电池的光电转换效率对推动该类电池的实际应用有着重要的意义,界面电荷复合过程的研究将有助于人们对广电转换的本质的认识,进而推动这种电池的光电性能的提高。我们以视黄酸吸附的TiO₂纳米胶体溶液为研究系统,发展了研究胶体溶液中TiO₂纳米粒子表面特性的瞬态分子探针方法,第一次用瞬态分子探针法研究了纳米颗粒尺寸效应对羧基在TiO₂纳米晶体表面键合形态影响。用纳秒时间分辨光谱研究染料敏化二氧化钛体系的电荷复合速率,证明其尺寸效应与表面键合态及Ti原子配位数之间的关系。这一研究有助于揭示界面电荷转移过程的微观机理,探索提高光电转换效率的新途径。我们用瞬态分子探针法研究了视黄酸分子ATRA在单个TiO₂界面上的电荷复合过程。用Marcus公式定量地计算了ATRA敏化TiO₂体系的界面电荷重排能,解决了国际上对Marcus公式的应用一直存在的困扰。发现并阐明了TiO₂纳米粒子胶体光致亲水、疏水变换的分子机制,首次定量阐明了该现象与Marcus重排能间的关系。在我们的研究中探针分子ATRA不仅可以作为探测TiO₂纳米粒子光致亲疏水性的探针,还可以作为探测重排能变化的探针分子。更多还原

【Abstract】 Perylene tetracarboxylic diimide（PDI） derivatives are important molecular building blocks that are currently being investigated for use in a variety of photoactive organic materials because of their low light and thermal fading rates, high luminescence efficiency,wide absorption and emission bands in visible region, and optoelectronic properties.They have been used in organic field-effect transistors, light-harvesting solar cells,photovoltaic devices,light emitting diodes,and robust organic dyes that are resistant to photobleaching.These dyes have generated great interest because of their outstanding photochemical and thermal stability,ease of synthetic modification,and desirable optical and redox characteristics.Driven by the demands of diverse applications,the modification on molecular structure of PDI aimed at changing the photophysical properties has attracted a lot of research interest in the past decade.Our research work has been focused on the following aspects:1.An Amphiphilic Perylenetretracarboxyl Diimide Dimer and its Application in Field Effect TransistorPerylene tetracarboxyl diimides（PDIs）,a category of organic dyes with excellent thermal and photo stabilities,have recently been intensively studied as good n-type semiconductor due to the high electron affinity caused by the electron-withdrawing imide groups.Different functional groups have been introduced at the imide nitrogen atoms of PDIs aimed at modifying the packing in solid state and thus improving the OFETs performance.Electron withdrawing groups,such as cyanide groups,introduced to the bay positions have been proved to improve the n-type semiconductivity significantly.Solution processed films of PDIs has been fabricated into OFETs and ambipolar transport properties for PDI was observed for the first time. We report the design,synthesis of a novel PDI compound with phenoxy groups at the bay positions and hydrophobic alkyl subsitutents at one of the two imide nitrogens of the PDI molecule.More interestingly,two of these PDI tings were linked by a hydrophilic triazine ring to form a PDI double-decker dimer with very good amphiphilic properties.Good OFETs performance using Langmuir-Blodgett（LB） films of this compound as active layer has been achieved with the carrier mobility as high as 0.05 cm² V^-1 s^-1 and current modulation of 10³ which is much better than that of the LB films fabricated from the corresponding PDI monomer.Our result revealed that pre-organizing the organic molecules into a stacked structure in solution by covalent bond before the film fabrication might be an efficient way to improve its OFET performance.2.Fluorescence Quenching in a Perylenetetracarboxylic Diimide TrimerThe most important process in natural photosynthetic reaction center is the quick and efficient multiple-step electron and the energy transfer.This has attracted many researchers to look for ways to duplicate the reactions in simplified chemical systems.In order to expatiate the ET process,sample and effective structure is very necessary.We designed and synthesisd a PDI trimer,which composed of three PDIs connected by a triazine ring.The monomer-dimer structure was confirmed by the steady state absorption spectra and the H¹NMR apectra.The fluorescence spectra indicate that the fluorescence of monomer has been quenched,suggesting the presence of ET from monomer to dimer in this trimer.To gain an insight into the ET from monomer to dimer in compound trimer,time-resolved transient absorption spectra were recorded. Our finding suggests that the ET can happen efficiently and quickly between a pair of non-interacted PDI monomer and dimer.We believe that this observation is meaningful for the design and construction of novel artificial LH systems. 3.Particle-Size-Dependent Hydrophilicity of TiO₂ Nanoparticles Characterized by Marcus Reorganization Energy of Interfacial Charge RecombinationSize-dependent hydrophilicity of TiO2 nanoparticles has been investigated by an interface transient molecular probe method.The results show that the reorganization energy for the interfacial charge recombination of the probe molecule can be a specific parameter for characterizing the hydrophilicity of the nanoparticles which is in accordance with the density of the surface hydroxyl group as a parallel parameter.The observed hydrophilicity in terms of either reorganization energy or the density of the surface hydroxyl group decays monoexponential with the mean particle diameter.This determination of the reorganization energy of the interfacial charge recombination can be a practical method for evaluating the hydrophilicity of nanoparticles other than TiO₂.更多还原