【作者】 孟繁夫；

【导师】 卢小泉；

【作者基本信息】 西北师范大学 ， 分析化学， 2008， 博士

【摘要】 卟啉及其金属配合物是一类具有刚性大环共轭体系的分子,生命体内存在的卟啉分子,其核心结构是卟啉的金属配合物。卟啉化合物在生命的氧化过程中起着氧的传输、储存、活化以及电子传递作用,具有特殊的生理活性。因此从卟啉分子的结构上认识和研究卟啉电化学性质是实验化学和理论化学关注的热点课题之一。密度泛函理论（DFT）是量子化学计算理论研究化学问题的理论计算方法之一。采用密度泛函理论计算得出分子构型、能量、原子电荷、电子密度以及分子轨道等性质,从而探寻分子的性质变化规律,解释化学实验现象,并为化学实验提供理论分析和指导。本文选用DFT理论对卟啉分子进行量化计算,研究了不同取代基、取代基个数和不同中心金属卟啉结构及性质的变化规律,在一定范围内预测金属卟啉的化学性质,为电化学研究卟啉分子提供理论支持。本论文分为四部分,概述内容如下:1.从量子化学的产生、发展和从头计算分子轨道理论,阐述了DFT的理论基础和在解决化学问题和卟啉电化学性质方面的应用,展望其研究的方向。2.苯环对位键连不同取代基四苯基Zn卟啉分子（ZnTPP-R）的几何优化和频率分析:选用B3LYP方法,C,N,O,H原子选用6-31G基组,Zn原子选用LanL2DZ和SDD赝势基组。结果如下:取代基对TPP分子变形性影响为-NO₂>-NH₂>-COOH>-OCH₃>-OH;选用6-31G/LanL2DZ基组比6-31G/SDD计算的MTPP-R分子结构更合理。四苯基Zn卟啉及五个不同取代基四苯基Zn卟啉分子电荷密度研究表明,在ZnTPP-R分子发生氧化反应时,电子经N原子或Cβ原子流出分子。轨道能量研究表明供电子取代基使分子LUMO+1,LUMO,HOMO,HOMO-1轨道能量升高,供电子能力越强,轨道能量增值越大;吸电子取代基使得分子LUMO+1,LUMO,HOMO,HOMO-1轨道能量降低,吸电子能力越强,轨道能量降低值越大;不同取代基四苯基Zn卟啉分子氧化电位由高到低为ZnTPPNO₂>ZnTPPCOOH>ZnTPP>ZnTPPOH>ZnTPPOCH₃>ZnTPPNH₂,还原电位由低到高为ZnTPPNO₂ < ZnTPPCOOH < ZnTPP < ZnTPPOH < ZnTPPOCH₃ <ZnTPPNH₂,不同取代基四苯基Zn卟啉催化活性由大到小ZnTPPNO₂>ZnTPPNH₂>ZnTPPOCH₃>ZnTPPOH>ZnTPP。3.取代基个数系列卟啉分子几何优化和频率分析:TPP（OH） 1-4选用B3LYP/6-31G基组,ZnTPP（OH）_1-4和ZnTPP（NO₂）_1-4选用B3LYP/6-31G-LanL2DZ基组。研究中心金属Zn,取代基种类、取代基个数、取代基位置不同对四苯基卟啉分子结构键长,键角和二面角的影响,结果如下:羟基、硝基、中心金属原子对TPP分子结构变化影响为中心金属原子>硝基>羟基;对卟啉电荷密度电荷分布作用影响为中心金属原子>硝基>羟基;对TPP氧化能力增强为羟基>中心金属Zn>硝基;苯基键连供电子取代基个数递增,氧化还原电位发生“负移”程度也递增,苯基键连吸电子取代基个数的递增,氧化还原电位发生“正移”程度也递增,TPP（OH）1-4氧化还原电位变化趋势与电化学实验结果吻合;供电子取代基与四苯基Zn卟啉苯环对位键连,取代基个数递增,分子催化活性递增,吸电子取代基与四苯基Zn卟啉苯环对位键连,取代基个数递增,分子催化活性递减。4.中心金属Fe、Co、Ni、Cu和Zn的MTPP,MTPPCOOH,MTPPNH₂等卟啉分子几何优化和频率分析,结果如下:Fe、Co、Ni、Cu、Zn原子对MTPP分子构型非平面扭曲程度为Ni>Co>Fe>Cu>Zn;对原子电荷密度研究表明,不同配位金属卟啉电化学反应电子转移的活性由大到小为NiTPP-R>CoTPP-R>FeTPP-R>CuTPP-R>ZnTPP-R;对十五个MTPP分子的前线轨道理论的HOMO-1,HOMO,LUMO,LUMO+1的轨道能量分析表明,MTPP、MTPPNH₂、MTPPCOOH分子中HOMO能量由高到低为ZnTPP-R>NiTPP-R>CuTPP-R>FeTPP-R>CoTPP-R。Fe,Co,Ni,Cu,Zn中心金属对MTPP-R分子的氧化还原电位影响较小。更多还原

【Abstract】 Porphyrins,as a class of the rigid ring conjugate molecule,exist in the way of metal porphyrin complexes. They are very important in the life science for oxygen and electronic transmission and so on. So they have a special physiological activity. Studying on structure of porphyrin molecules of porphyrin electrochemical nature by the experiment chemistry and theoretical chemistry is one of the hot topics.Density Functional Theory （DFT）, by which the quantum chemistry calculation is applied effectively in study on the issuers of chemistry, is one of the theoretical calculation method. The molecular characters including configuration, energy, atomic charge, electron density and molecular orbital can be obtained by DET. From these charactors the chemical phenomena of moleculer can be explained. The results of DET study can guaid theratically the chemical experiment.This paper analyses the electrochemical nature of mental meso-tetraphenylporphyrin porphyrin （MTPP） with the different substitutions with the quantum chemistry calculation method, forecasts the electrochemical properties of similar substitution complexes,and the DFT calculations provide support for the electrochemical experimemns theoretically.The paper is divided into four parts outlined as follows:1. In this section the theoretical foundation of DFT is simply introduced firstly in aspects of the foundation of quantum chemical and it’s calculations on the basic of the frequency analysis, charge density distribution and Mulliken charge. Then the application of DFT in solving chemical problems and in study of porphyrin moleculars are described, followed by the forecasting aspects of the field.2. The B3LYP calculation study on the difference of substitutions in ZnTPP: -OH, -OCH₃, -NH₂ are selected as electron-donating groups, and -COOH, -NO₂ are selected as electron-withdrawing groups, all them are connected to the site of 4-benzene. In the calculation, 6-31G basis set is selected for C, N, O and H atom, LanL2DZ and SDD pseudopotential basis sets are selected for Zn atoms. The computational calculations are performed with the Gaussian 03 software package. The effects on bond lengths, bond angles and the dihedral angle parameters of the molecular structure are analyzed.The results indicate the effect of substitutions on the shape of ZnTPP is -NO₂>-NH₂>- COOH>-OCH₃>-OH. The better optimized effect is obtained when using LanL2DZ pseudopotential basis set than SDD one. The research of Mulliken charge indicates that the electron flow out the molecular from N or Cβatom when oxidizing. The electron-donating groups enhance the LUMO+1,LUMO,HOMO,HOMO-1 energy, and the stronger the ability of electron-donating, the more of the energy enhancement, while the electron-withdrawing groups decrease the LUMO+1,LUMO,HOMO,HOMO-1 energy, and the stronger the ability of electron- withdrawing, the more of the energy decrease. The oxidation potential of ZnTPP-Rs are sequence as ZnTPPNO₂>ZnTPPCOOH>ZnTPP>ZnTPPOH>ZnTPPOCH₃>ZnTPPNH₂, the reduction potential of ZnTPP-Rs are sequence as ZnTPPNO₂<ZnTPPCOOH<ZnTPP<ZnTPPOH<ZnTPPOCH₃<ZnTPPNH₂,and their catalytic activity are sequence as ZnTPPNO₂>ZnTPPNH₂>ZnTPPOCH₃>ZnTPPOH>ZnTPP。3. The calculation study based on the different mental, different site and number of substitutions: B3LYP/6-31G-basis set is used in the TPP（OH）1-4, and B3LYP/6-31 G-LanL2DZ-basis set for ZnTPP （NH₂） 1-4 and ZnTPP （NO₂） 1-4. The effects of the number and the positions of substituents on the molecular structure of porphyrin are researched.The results indicate that the effect trend of -OH, -NO₂ and M on the structure of TPP is M>-NO₂>-OH, and a same trend on Mulliken charge is obtained too. But the trend of enhancement for oxidation activity of TPP is different, that is -OH>M>-NO₂. The negative shift of radox potential increases with the increase of the number of the electron-donating groups, and its positive shift increases with the increase of the number of the electron-withdrawing groups. The HOMO,LUMO energy changing trend of ZnTPP-Rn obtained by the calculation is agree with the results of electrochemical experiments. In ZnTPP-Rn（R=electron-donating groups）, the catalytic activity increases with the increase of n, and in ZnTPP-Rn（R=electron-withdrwing groups）, the catalysis decreases with the decrease of n。4. The calculation study basices on MTPP （M=Fe, Co, Ni, Cu, Zn）, MTPPCOOH（M=Fe, Co, Ni, Cu, Zn） and MTPPNH₂ （M=Fe, Co, Ni, Cu, Zn）. The results indicate the effect of different metals on the shape of TPP is Ni>Co>Fe>Cu>Zn. The research of the Mulliken charge indicates that the effect of different metals on the electron transfer activity on surface of electrode and liquid/liquid interface is NiTPP-R>CoTPP-R>FeTPP-R>CuTPP-R>ZnTPP-R. The research of the energy of HOMO-1, HOMO and LUMO, LUMO +1 for fifteen MTPPs indicates that in MTPP, MTPPCOOH and MTPPNH₂ , the energy of HOMO is ZnTPP-R>NiTPP-R>CuTPP-R>FeTPP-R>CoTPP-R.Electrochemical activity of MTPP-R is forecasted by analyzing the Electron-density distributions of MTPP-R. The metal of Fe, Co, Ni, Cu and Zn has the lower effect on redox potential of MTPP-R。更多还原