【作者】 王路；

【导师】 张红雨；

【作者基本信息】 吉林大学 ， 有机化学， 2018， 博士

【摘要】 有机共轭发光材料在有机电致发光、有机固体激光、荧光生物成像、传感等领域应用前景十分广泛。并环结构有机小分子具有易于修饰的特点。刚性并环结构有效地避免了分子的无序性,从而使发光性质变得更为独特。在环中掺杂具有独特性能的主族元素是设计有机共轭分子的发展趋势。其中含有硼元素的有机硼配合物已被证明是一种高效发光材料。在构建有机四配位硼配合物时,由于硼原子具有空位p轨道,所以有机硼对双键配体具有较高的反应活性,不仅可以形成具有并环结构的四配位硼桥环,还可以引起π体系分子内的电子离域。形成的环状结构可以有效地限制分子旋转,从而提高荧光效率。此外,刚性的π体系可以降低最低未占分子轨道(LUMO),这又可以提高配合物的电子亲和力。通过改变配体或配体上的取代基,有机硼配合物可以比较容易获得理想的性质。通过科研工作者的努力,近来已经构筑了许多发射颜色从深蓝到近红外的有机四配位硼配合物,并且其中一些在固体状态下有较强荧光发射。物质的结构决定了性质,深刻理解结构与性质之间的关系是开发高性能材料的前提。有机晶体具有明确的单分子和分子内聚集态结构,是研究结构与性质关系的理想体系。在本文研究工作中,我们通过简单有效的路线设计合成了一系列具有共轭结构的双苯基β-二酮有机硼配合物,仔细研讨了他们的晶体结构和光物理性质。1、在第二章中,我们通过简单的酮酯缩合反应,以较高产率合成了配体1–4。将苯基硼化合物(三苯基硼、二-5-氟苯基氟化硼)与配体反应,重结晶提纯后分别得到配合物1–8。通过核磁共振、质谱和元素分析等表征方法对配合物的结构进行确认。2、在第三章中,我们研讨了配合物3的发光性质。配合物3制备出橙色3OC与红色3RC两种晶相,两种晶相在分子排列方式上的不同导致了其在发光上的差异。晶体3OC在分子内形成分子二聚体,二聚体排列成一种特殊的网状结构,相比于其他排列方式,这种结构不够稳定,通过外力的刺激,晶体排列方式易发生变化。当敲击晶体,晶体碎裂成小块,在敲击应力的作用下,晶体断裂,在产生的断裂面发光明显蓝移并且增强。这是因为二聚体之间相对较弱的超分子作用被破坏,同时二聚体之间的距离变大,这相当于解聚集的过程,因而荧光蓝移,效率变高。在研磨压力的作用下,晶体变为无定形粉末,发光红移并且变暗。这源于在各向异性剪切力的作用下,分子的排列方式发生变化,二聚体间距离缩小,形成较强的二聚体间π???π相互作用,这相当于聚集的过程,因而荧光红移,效率变低。然而,我们对晶体施加各向同性静水压力,在超高压的作用下,分子间排列更加紧密,缩小了分子间距离。进而增强晶体内超分子作用,分子进一步聚集。基于这样一个模型体系,我们不仅揭示了分子间超分子作用距离对材料发光性能的影响,而且首次获得了三种不同压力对材料发光性质完全不同的响应特性。3、在第四章中,我们研讨了配合物4的光物理性质。通过晶体生长,配合物4制备出橙色晶体4OC和红色晶体4RC。我们采用多种刺激方式使橙色晶体的发光颜色发生变化。一、在经过简单的机械研磨后,橙色晶体4OC变为红色的固体粉末,发射峰位由580 nm变化至610 nm。进一步地对材料进行高压实验,在各向同性的高压下,发射峰位红移到655 nm。二、加热橙色晶体4OC,其荧光发射也会发生变化,当将其升温至235℃,荧光发生蓝移,变为绿光发射(520nm),这一加热变温过程是可以多次重复的。三、配合物上的二甲胺基易于被质子化,通过影响分子的电子特性从而使发光性质发生变化。将配合物4置于强挥发性酸氛围中,配合物发光峰位蓝移至450 nm。通过挥发性酸的刺激,配合物表现出蓝色荧光发射。以上三种荧光变化过程均是可逆的。基于上述研究,我们通过对一种配合物的刺激,实现了红绿蓝三基色发光。4、在第五章中,我们研究了对称取代的β-二酮硼配合物5–8,并仔细的研究它们的光物理性质。这四种配合物的固体均为红光发射,其中配合物5和6发光效率分别达到了0.32和0.48。这样发光效率,在红色发光材料中相当突出。配合物7和8发光较弱,所以我们重点对比研究配合物5和6。通过晶体生长,配合物5–8均制备出晶体,其中配合物5制备出红色长条状晶体5a和红色块状晶体5b两种晶相,配合物6制备出红色块状晶体6a和红色针状晶体6b两种晶相。在二氯甲烷溶液中,两种配合物分别表现出明亮的绿色和蓝绿色荧光。同时,我们发现晶体5a和晶体6b具有放大自发发射现象,从而证明了四配位硼有机材料在有机激光领域具有潜在的应用价值。综上所述,我们设计合成了八种基于双苯基-β-二酮的有机硼配合物,仔细研究了他们的光物理性质和晶体结构。有趣的是其中一些配合物对外界刺激产生荧光变化。基于此类配合物的研究,对揭示结构与性能关系这一材料科学领域中重大的科学问题具有重要意义。同时,对有机四配位硼配合物的后续研究工作提供了参考。更多还原

【Abstract】 Luminescent π-conjugated organic materials have been widely used in the applications of optoelectronics,including organic light-emitting diodes(OLEDs),organic solid-state lasers(OSLs),chemsensing,bioimaging and etc.The ring-fused structures of organic compounds are easily modified and can effectively circumvent the disorder of the molecules,thereby making the luminescent properties more unique.The doping of a main-group elements with unique properties in the ring is a developed trend in the design of organic conjugated molecules.The organoboron compounds which contain boron element have been proved to be a family of high-efficiency luminescent materials.Organoborane reagents have high reactivity towards bidentate organic ligands due to the vacant p-orbital of the boron atom,which can not only allows the formation of a rigid four-coordinate boron-bridged ring but also causes intramolecular electron delocalization of the π-system.The produced ring-fused structures can effectively constrain the molecular rotations and hence may intensify the emission.In addition,the rigidified π-system may decrease the lowest unoccupied molecular orbital(LUMO)level,which in turn endows the formed boron-containing materials with high electron affinity.By changing the substituents on the ligands,the organoboron compounds can obtain the desired properties more easily.Through the efforts of scientific researchers,many organic tetra-coordinate boron compounds emitting from dark blue to near-infrared luminescence have been recently constructed,and some of them have strong fluorescence emission in the solid state.The structure of a material determines the properties and a deep understanding of the relationship between structure and properties is the prerequisite for the development of high-performance materials.Organic crystals have a well-defined single-molecule and intramolecular aggregation structure and are ideal systems for studying the relationship between structure and properties.In this research,we synthesized a series of boron diaryl-β-diketonate compounds with conjugated structures through simple and effective routes,and carefully studied their crystal structure and photophysical properties.1.In Chapter II,we synthesized ligands 1–4 with high yields by a simple Claisen condensation reaction.The phenyl boron reagents such as triphenylborane and fluorobis(pentafluorophenyl)borane reacted with the ligands,and the compounds 1–8 were obtained after purification by recrystallization.The structure of the compounds was confirmed by characterization methods such as NMR spectra,mass spectra,and elemental analysis.2.In Chapter III,we studied the luminescent properties of Compound 3.Compound 3 produced two polymorphs,orange-emissive 3OC and red-emissive 3RC.The difference in the arrangement of the two crystal phases led to the difference in their luminescence.Molecules in crystal 3OC form dimers and the dimers are arranged in a special network structure,which is less stable than other arrangements.Through the stimulation of external forces,the crystal arrangement tends to change,The crystal is fragmented into small pieces when it is smashed,and under the action of the tensile force,the crystal is broken,and the generated fracture surface emits significantly blue shift fluorescence with increased emission intensity.This is because the relatively weak supramolecular interaction between dimers is destroyed,and the distance between dimers becomes larger,which is equivalent to the process of disaggregation,and the fluorescence is blue shifted and the efficiency becomes higher.Under the effect of grinding pressure,the crystals become amorphous powder,and the light emission is red-shifted and darkened.This is due to the fact that under the action of anisotropic shear forces,the arrangement of molecules changes and the distance between dimers decreases,forming a strong π interaction between dimers,which is equivalent to the aggregation process.As a result,the fluorescence red shift and the efficiency become lower.We also apply isotropic hydrostatic pressure to the crystals.Under the action of ultra-high pressure,the molecules are arranged more closely and the distance between molecules is reduced.In turn,the intramolecular supermolecular effect is enhanced,and the molecules further aggregate tightly.Based on such a model,we not only revealed the influence of the distance between supramolecular molecules on the luminescent properties,but also obtained the response characteristics of three different pressures on the luminescent properties of the material for first time.3.In chapter IV,we studied the photophysical properties of compound 4.By crystal growth,compound 4 produces orange crystals 4OC and red crystals 4RC.First,after a simple mechanical grinding,the orange crystals turned to a solid powder,and the emission peak changed from 580 nm to 610 nm.The material was further subjected to a high pressure test and the emission redshifted to 655 nm under isotropic high pressure.Second,heating the orange crystal 4OC,its fluorescence emission will also change,when it is heated to 235°C,the fluorescence blue shift and display a green light emission(520 nm).The third,the dimethylamine group on the compound is prone to protonation and changes the luminescent properties by affecting the electronic properties of the molecule.Compound 4 was placed in a strong volatile acid atmosphere and the emission peak of the compound shifted to 450 nm.The above three process are reversible.Based on the above studies,we achieved red,green,and blue primary colors by stimulating a single compound.4.In Chapter V,we studied symmetrically substituted boron diaryl-β-diketonates complexes 5–8 and carefully studied their photophysical properties and explored their applications.The solids of these four compounds were all red emissive,and the efficiencies of compounds 5 and 6 reached 0.32 and 0.48,respectively.This efficiency is quite prominent in red luminescent materials.Considering that the fluorescence efficiency of compounds 7 and 8 much lower than that of 5 and 6,we focused on comparative studies of compounds 5 and 6.Through crystal growth,Compounds 5–8 all produce crystals suited for X-ray single crystal diffraction.Compound 5 produced two polymorphs,red colored form 5a with flake-like morphology and orange-red colored form 5b with a block shape.Compound 6 also produced two polymorphs,red block crystal 6a and red needle crystal 6b.Both compounds showed bright green and greenish-blue fluorescence in dichloromethane solution,respectively.At the same time,we have found that crystal 5a and crystal 6b show amplified spontaneous emission(ASE)phenomena,thus demonstrating the potential application of four-coordinate organoboron materials in the field of organic lasers.In summary,we designed and synthesized eight organoboron compounds based on diaryl-β-diketonates,and carefully studied their photophysical properties as well as crystal structure.What is interesting is that some of these compounds produce fluorescent changes to external stimuli.Based on the research of such compounds,it is of great significance to reveal the relationship between structure and properties,a major scientific issue in the field of materials science.At the same time,it provides reference for the follow-up study of tetra-coordinate organoboron compounds.更多还原