【作者】 孙侨；

【导师】 廖奕； 苏忠民；

【作者基本信息】 东北师范大学 ， 物理化学， 2010， 硕士

【摘要】 王悦课题组设计合成了蒽的衍生物(ANP),该有机发光分子通过分子间弱相互作用,在不同的晶体生长条件下形成五种超分子单晶,这五种晶体发光颜色不同,分别发蓝光、蓝-绿光和绿光(Adv.Mater.2006,18,2369-2372)。以往通过对有机分子取代基的修饰来调节光物理性质,其实通过分子间非共价作用调节分子的堆积结构(即多晶相现象)同样可以实现上述目标。多晶相现象是晶体学上的常见现象,是指某一分子通过分子间堆积形成两种或两种以上晶体的现象。王悦课题组设计合成了蒽的衍生物,该有机发光分子在不同的晶体生长环境下分别通过分子间氢键和π…π相互作用导致分子聚集状态的差异,使发光颜色有所改变。从而形成五种超分子单晶。这种基于同一分子的不同堆积带来不同晶体发光颜色的改变的同分子多晶相体系,是探讨结构和性能关系的理想结构模型。为深入探讨单分子和聚集体结构与光物理性质之间的关系,我们借助量子化学方法研究了不同堆积体系的结构、分子间相互作用和光谱性质。采用密度泛函理论(DFT)B3LYP /6-31G*方法,优化了单分子和三聚体的基态几何构型,采用单组态相互作用(CIS/6-31G*)方法优化分子的最低激发单重态几何构型。用含时密度泛函理论(TDDFT)计算分子的吸收和发射光谱。研究结果表明,单分子通过弱相互作用形成聚合物,有利于提高分子的稳定性。对比三聚物和单分子的能量可知,单分子聚集后能量降低,结构更加稳定。同时对于聚合物体系光谱性质的研究表明,分子间氢键作用对光谱性质的影响很小,但通过H键聚集起到支撑骨架的作用,而使发光强度有所提高;而分子间π…π相互作用对有机分子的发光性质具有重要影响,前线分子轨道主要成份分布在具有π…π作用的配体上,跃迁性质发生改变,导致光谱发生部分红移。更多还原

【Abstract】 Wang et al. have designed and synthesized five luminescent polymorphs by tuning the molecular assembly structures in crystals (Adv.Mater.2006, 18, 2369-2372) which show different colors.In the past, we usually modify of the substitute group to regulate the photo physical properties, whereas the non-covalent intermolecular interactions are able to strongly influence the final packing structure, make polymorphism existence. Polymorph is a solid crystalline phase of a given compound resulting from the possibility of at least two different arrangements of the molecules of that compound in the solid states, which is a widespread phenomenon.Wang et al. have designed and synthesized anthracene derivatives, under specific circumstances, crystals with different colors were achieved, which can be attributed to weak interactions between molecules leading to distinctive aggregation. Different polymorphs base on the same single molecular may have very different physical and chemical properties, and therefore represent special situations for the study of structure-property relationships.To reveal the relationship between different molecular packing and emission colors, theoretical analysis of spectral properties and electronic structures of these complexes were systematically characterized. The geometric and electronic structures of the complexes in the ground state are studied with density functional theory (DFT) ,whereas the lowest singlet excited states are optimized by ab initio CIS. To assign the absorption and emission peaks observed in the experiment, we computed the spectrum of the lowest singlet excited states with time-dependent DFT (TD-DFT). All DFT calculations were performed using the B3LYP functional and the 6-31G* basis set.This work suggests that, the anthracene derivatives accumulate into trimers via hydrogen bonding have a little influence on the shift of the spectra, but can increase the luminous intensity and play the role of supporting the trimer skeleton. At the same time, the intermolecularπ...πinteraction between the organic light-emitting elements has an important impact on the luminescent properties and lead to red shifts of emission spectra.更多还原