几种含氮杂环化合物激发态分子内质子转移研究

发布时间：2018-05-03 04:27

本文选题：氢键 + 激发态质子转移　；参考：《湖南科技大学》2017年硕士论文

【摘要】：质子转移广泛存在于自然界中,是化学和生物领域中的重要反应。激发态质子转移在物理和生物系统中扮演着十分重要的角色,近年来越来越多的研究者从实验和理论方面来探究激发态分子质子转移的性质。本论文采用量子化学计算方法探讨了[2,2-联吡啶]-3,3-二醇(Bp(OH)2)、10-羟基苯并喹啉(HBQ)等含氮杂环化合物激发态分子内质子转移机理及其性质,为此类分子的设计提供了一定的理论基础。同时,结合光谱实验,考察了溶剂、温度以及在瓜环的超分子作用下对HBQ质子转移的影响。1.采用密度泛函(DFT)和含时密度泛函(TD-DFT)计算方法研究了Bp(OH)2的激发态分子内双质子转移(ESIDPT)性质。通过对键长、键角、红外振动光谱以及氢键键能的分析,发现Bp(OH)2分子从基态光致激发到达第一激发态后,分子内双氢键显著加强,而分子内氢键的加强促进了激发态质子转移。质子转移的势能面表明,在基态和激发态时均能发生单质子和双质子转移,且激发态的双质子转移是分步进行的,在实验中出现的斯托克位移变化可以根据ESIDPT机理得到较好的解释。2.运用密度泛函(DFT)和含时密度泛函(TD-DFT)计算方法研究了HBQ及其衍生物分子内质子转移过程,考察了取代基效应对质子转移过程的影响。研究发现,HBQ及其衍生物可以形成分子内氢键,且激发态时氢键增强。基态时各分子以醇式构型稳定存在,激发态时酮式构型为优势构象。各化合物的最大吸收峰主要是电子从HOMO到LUMO之间的跃迁引起的。基态分子内质子转移(醇式→酮式)需要跃过较高的能垒因而难以发生,而激发态时只需跃过较低能垒就很容易发生分子内质子转移,吸电子基的引入可以使该过程的能垒降低,因此吸电子基有利于激发态质子转移。取代基效应影响化合物的光谱性质。3.采用荧光光谱法并结合量子化学理论计算,研究了溶剂、温度以及七元瓜环的超分子作用对HBQ质子转移的影响。结果表明,极性溶剂在一定程度上促进了HBQ激发态质子转移。瞬态荧光的研究可知,随着七元瓜环的加入其量子产率增加。根据与七元瓜环相互作用的荧光光谱及理论计算结果表明HBQ与七元瓜环形成了1:1的包合物。运用量子化学理论方法考察了溶剂对HBQ质子转移过程中势能曲线的影响,根据模拟出的势能曲线可以推测出极性溶剂促进了分子内激发态质子转移,从而促使醇式到酮式的转变,使长波处荧光增强,这与实验数据得出的结论一致。
[Abstract]:Proton transfer exists widely in nature and is an important reaction in chemical and biological fields. Excited proton transfer plays a very important role in physical and biological systems. In recent years, more and more researchers have explored the properties of excited state proton transfer from experimental and theoretical aspects. In this paper, the quantum chemical method is used to study the mechanism and properties of the excited states of [2 (2) -bipyridine] -3- (3) -diol (BpOHN) (10-hydroxybenzo-quinoline (HBQ), which provide a theoretical basis for the design of this kind of molecules. At the same time, the effects of solvent, temperature and supramolecular action of melon ring on the proton transfer of HBQ were investigated. The properties of excited intramolecular double proton transfer (Bp(OH)2) in Bp(OH)2 have been studied by density functional theory (DFT) and time-dependent density functional spectroscopy (TD-DFT). Based on the analysis of bond length, bond angle, infrared vibrational spectrum and hydrogen bond energy, it is found that the intramolecular double hydrogen bond is significantly strengthened when the Bp(OH)2 molecule is excited from the ground state to the first excited state, and the enhancement of the intramolecular hydrogen bond promotes the proton transfer in the excited state. The potential energy surface of the proton transfer shows that both the elementary and the double proton transfer can occur in the ground state and the excited state, and the double proton transfer of the excited state is carried out step by step. The Stoke displacement can be explained according to the ESIDPT mechanism. The intramolecular proton transfer processes of HBQ and its derivatives were studied by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The effect of substituent effect on the proton transfer process was investigated. It is found that HBQ and its derivatives can form intramolecular hydrogen bonds, and the hydrogen bonds are enhanced in excited states. In the ground state, the alcohol-type configuration is stable, and the ketone configuration is the dominant conformation in the excited state. The maximum absorption peaks of the compounds are mainly caused by the transition of electrons from HOMO to LUMO. The intramolecular proton transfer in the ground state (alcohol-ketone type) is difficult to occur due to the need to leap over the higher barrier, while the intramolecular proton transfer is easy to occur in the excited state by simply jumping over the lower barrier. The energy barrier of the process can be reduced by the introduction of the electron-absorbing group, so the electron-absorbing group is advantageous to the proton transfer in the excited state. The substituent effect affects the spectral properties of the compounds. The effects of solvent, temperature and supramolecular interaction of seven-member melon ring on HBQ proton transfer were studied by fluorescence spectroscopy and quantum chemical theory. The results show that polar solvents can promote the proton transfer of HBQ excited state to some extent. The study of transient fluorescence shows that the quantum yield increases with the addition of seven-member melon ring. According to the fluorescence spectra and theoretical calculations of the interaction between HBQ and the seven-member melon ring, the inclusion complex of 1:1 was formed between the HBQ and the seven-member melon ring. The influence of solvent on the potential energy curve of HBQ proton transfer was investigated by using quantum chemical theory. According to the simulated potential energy curve, it can be inferred that polar solvents promote intramolecular excited proton transfer. Thus, the conversion of alcohol form to ketone form is promoted, and the fluorescence at long wave is enhanced, which is consistent with the conclusion of experimental data.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O626

【参考文献】