【作者】 周小青；

【导师】 孙延波；

【作者基本信息】 吉林大学 ， 物理化学， 2010， 硕士

【摘要】 荧光传感器是近年来学术和生物化学研究的热门课题,并且应用于哺乳动物心血管、免疫和神经系统方面。一氧化氮(NO)是生物体内的一种信使分子和效应分子,在生理和病理过程中起着重要的作用,对心脑血管系统、消化系统、神经系统均具有重要的调节作用。利用荧光传感器在生物体内检测NO的含量就成为了生物学家、化学家等关注的热门课题。尤其是荧光探针的出现,更是吸引了大量科学家的兴趣。因此,对该类荧光物质的结构、性质及吸收光谱的研究是非常有价值的。本文还介绍了三种红色发光物质—铱(Ⅲ)配合物,在密度泛函DFT理论下,应用B3LYP的方法对基态构型进行了全优化,用CIS方法计算最低三重激发态。这些配合物没有对称性限制。在基态和激发态几何优化的基础上,在PCM二氯甲烷(CH2Cl2)溶剂中,采用TDDFT/B3LYP计算光谱,以获得单态(Sn)和三重激发态(Tn)的垂直激发能。所有的计算均采用高斯03程序包。主要成果如下:1.我们使用DFT理论方法对一系列FLn及其与NO反应后的产物FLnNOm(m=1-3)的分子结构进行了全优化,对其键长键角的变化做了详细的对比分析,同时还探究了NO+对FLnCu荧光探针的三种进攻部位。通过对这一系列物质的频率的计算,证明这些结构式的稳定性,计算都是在B3LYP/6-31G**理论基础上,由Gaussian 03数据包完成的。计算结果表明,NO+进攻羟基邻位即生成FLnNO2的能量是最低的。同时我们还利用不同基组B3LYP/6-311++G**做了对比试验,结果表明,基组的增加对其结果的优化影响作用是微小的,而溶剂化效应是显著的。我们利用含时密度泛函理论(TD-DFT)方法对上述物质的吸收光谱做了深入的研究,通过对其强度的对比分析,得出吸电子取代基,通常能够使LUMO轨道能量升高,HOMO轨道能量下降,致使LUMO与HOMO之间的能量差增加,从而导致它们的最低吸收波长发生蓝移,反之,斥电子取代基会导致最低吸收波长发生红移。2.量子化学不仅研究电子结构,吸收光谱,而且还研究磷光机制以及电致发光(EL)性质,本文还介绍了三种红色发光物质—铱(Ⅲ)配合物,(fpmqx)2Ir(L) (fpmqx= 2 (-4 -氟苯基)- 3 -甲基喹喔啉; L为triazolylpyridine (trz) (1),L为picolinate (pic) (2)和L为acetylacetonate (acac) (3)。计算结果表明,1的HOMO主要分布于trz基团,因为trz是强π-电子接受体,而2和3的HOMO主要是铱d轨道和苯环π轨道组合。此外我们还分析比较了上述三类配合物磷光产量的高低和电致发光效率的差异。我们使用DFT和TDDFT方法,对3种Ir (Ⅲ)配合物(fpmqx)2Ir(L)进行了几何全优化,分析了电子结构以及磷光光谱,并对电致发光机理进行探讨和研究。计算结果表明,trz比pic与acacπ电子受体能力强,导致1的HOMO分布于trz,而2和3分布于Ir的d轨道和苯环π轨道。1-3最低能量吸收主要贡献在于HOMO→LUMO跃迁,由于有较大的HOMO与HOMO-1、LUMO与LUMO +1能隙,它们都拥有MLCT,LLCT和ILCT混合跃迁特征。此外,2比1和3有更高的电致发光效率,原因是2与α- NPD和LiF/Al相比有相对较小的HOMO和LUMO的能量差,而且它可以改善空穴或电子注入效率且将重组区限制在发光层。当然,其它因素,例如温度和环境也会引起这些配合物的磷光效率的差异。更多还原

【Abstract】 Fluorescent sensors have been the subject of considerable academic and biochemistry research in recent years because of their possible applications in the mammalian cardiovascular, immune and nervous systems. Consequently, detection of NO levels in vivo becomes a popular topic for biologists, chemists, etc.. In particular, the appearance of fluorescent probe for detecting NO molecule in vivo is of great interests to a large number of scientists. Therefore, the research on the structures, properties and absorption spectrum of such fluorescent materials is very valuable.Three red-emitting Ir(III) complexes, (fpmqx)2Ir(L) {fpmqx=2-(4-fluorophenyl)-3-methyl-quinoxaline; L= triazolylpyridine (trz) (1); L= picolinate (pic) (2) and L= acetylacetonate (acac) (3)} were introduced in the present paper. The ground-state geometries were fully optimized at DFT level using the B3LYP method, and the lowest-lying triplet excited-state geometries were calculated with the single excitations (CIS) approach. There were not any symmetry constraints during the structural optimizations. optimized by DFT with Becke’s LYP (B3LYP) exchange-correlation functional and the configuration interaction with single excitations (CIS) approach. There were no symmetry constraints among these complexes. On the base of respective optimized geometries of ground and excited states, the TDDFT/B3LYP method is applied to calculate the spectrum associating with the polarized continuum model (PCM) in dichloromethane (CH2Cl2) media in order to obtain the vertical excitation energies of singlet (Sn) and triplet (Tn) states. All calculations were performed with Gaussian 03 program package.The main results are as follows:1. By using the theoretical method of DFT and TD-DFT we optimized the geometries of a series of FLn and FLnNO1, FLnNO2, FLnNO3 fluorescent materials. And we also made a detailed analysis on the changes of bond lengths and angles. Meanwhile, we explored three positions of NO+ to offense the FLnCu fluorescent probe. We demonstrated the stabilities of these structures by frequency calculations. All of the calculations on these fluorescent complexes have been performed at the B3LYP/6-31G** level using the Gaussian 03 program package. The results show that the energy of FLnNO2 generated by NO+ attacking the o-OH position was the lowest. Meanwhile, we also made a comparison test using different basis set 6-311++G** at the same B3LYP level. The results showed that influence of the increase in basis functions on the optimization is small, and the solvent effects are remarkable. We made a deep research in the absorption spectrum of above mentioned materials by means of the time-dependent density functional theory (DFT) method. Through the comparative analysis of the strengths of absorption spectrum, we can see that strong electron-withdrawing group can increase the energy of LUMO orbital, and decrease the energy of HOMO orbital, which leads to the increase of HOMO-LUMO gaps. Finally, their minimum absorption is blue shifted. Conversely, the electron-pushing group leads to red shifted minimum absorption.2. Quantum-chemistry study was applied to investigate the electronic structures, absorption and phosphorescence mechanism, as well as electroluminescence (EL) properties. Three red-emitting Ir(III) complexes, (fpmqx)2Ir(L) {fpmqx=2-(4-fluorophenyl)-3-methyl-quinoxaline; L= triazolylpyridine (trz) (1); L= picolinate (pic) (2) and L= acetylacetonate (acac) (3)} were introduced in the present paper. The calculation shows that the HOMO distribution for 1 is mainly localized on trz moiety due to its strongerπ-electron acceptor ability, and HOMOs for 2 and 3 are mainly the combination of Ir d- and phenyl ringπ-orbital. The differences of phosphorescence yields and electroluminescence efficiencies among 1-3 are also investigated in this paper. The geometrical and electronic structures, and the phosphorescence spectrum and electroluminescence properties of three Ir(III) complexes (fpmqx)2Ir(L) were investigated using the DFT and TDDFT methods. The computational results reveal that, strongerπ-electron acceptor ability of trz than pic and acac results in the HOMO distribution residing on the trz moiety for 1, and those localized on Ir d- and phenyl ringπ-orbital for 2 and 3. The lowest energy absorption for 1-3 is mainly HOMO→LUMO transition configuration. Due to the large HOMO and HOMO-1, LUMO and LUMO+1 energy gaps, all of them have mixed transition characters of MLCT, LLCT and ILCT. In addition, the higher electroluminescent efficiency of 2 than 1 and 3 comes from the relative smaller HOMO or LUMO energy differences between 2 andα-NPD and LiF/Al, which can improve the hole or electron injection efficiency and confine the recombination zone within the light-emitting layer. Certainly, other factors, such as different temperature and environment can also resulting in different phosphorescent efficiencies among these complexes.更多还原