一类染料分子和抗生素分子激发态性质的理论研究

发布时间：2018-08-09 20:21

【摘要】：分子光化学的研究领域包括分子的光化学反应和分子的光物理变化。基态分子吸收光子,发生电子轨道跃迁形成激发态。同时引起分子的几何构型、分子轨道电荷分布、分子极性和偶极矩等激发态性质发生改变。因此,研究分子的电子激发态的分子结构、电子性质和动力学过程,对理解染料分子和抗生素分子的光化学反应和光物理过程,非常重要。抗生素的过度使用及排放,严重污染水环境及人类健康,通过激发态发生光化学反应是有效降解方式。本文采用密度泛函和含时密度泛函理论方法,计算分子几何平衡结构、光谱数据和前线分子轨道等数据,比较不同电子态下的氢键强度、几何构型、电子布局数等变化,研究染料分子和抗生素分子的激发态结构及性质。首先,采用CAM-B3LYP杂化泛函,6-311++G (d,p)基组,CPCM溶剂化模型,研究了对硝基联苯酚-三甲基叔丁基胺氢键复合物的激发态性质。计算得到紫外光谱最大吸收峰为333 nm,实验值为354 nm,符合良好；对比不同电子态中氢键键长、氢键结合能以及红外光谱,得到了激发态结构,发现了N-H+的生成,验证了实验中观测到的电子-质子转移现象；比较电子激发能和振子强度,说明S1态是主要激发态；分析前线分子轨道,说明S1态是分子内电荷转移激发态,具有π-π*跃迁特征,为实验提供了有用的理论信息。其次,采用B3LYP杂化泛函,6-311-1+G (d,p)基组,水的CPCM溶剂化模型,研究了氯四环素-水分子氢键复合物的激发态性质。计算得到紫外光谱最大吸收峰为370nm,实验值为367 nm,符合良好；对比不同电子态的构型和振动光谱,发现在激发态,分子内的电荷转移伴随着分子间质子转移现象,说明氯四环素-水分子相互作用在激发态得到增强；比较电子激发能和振子强度,说明主要激发态是S2态,且S1态和S2态均为是局域激发态；分析前线分子轨道,说明S1态和S2态均为分子内电荷转移激发态。最后,采用B3LYP杂化泛函,6-311++G(d,p)基组,水的CPCM溶剂化模型的方法,研究了诺氟沙星-水分子氢键复合物的激发态性质。计算得到紫外光谱最大吸收峰为277 nm,实验值为272 nm,计算红外光谱C37=038吸收峰1734 cm-1,实验值1731cm-1,符合良好；对比不同电子态中氢键键长以及红外光谱,说明分子内氢键在激发态得到增强并且S4态的分子内氢键比在S1态的分子内氢键更强；比较电子激发能和振子强度,说明主要激发态有S1、S2、S4和S6态；分析前线分子轨道和NBO,说明S1态和S4态均有π-π*跃迁特征,且S1态是扭转的分子内电荷转移激发态。
[Abstract]:The research fields of molecular photochemistry include the photochemical reaction of molecules and the photophysical changes of molecules. The ground state molecule absorbs photons, and the electron orbital transition takes place to form an excited state. At the same time, the molecular geometry, molecular orbital charge distribution, molecular polarity, dipole moment and other excited state properties are changed. Therefore, it is very important to study the molecular structure, electronic properties and kinetic processes of electron-excited states in order to understand the photochemical reactions and photophysical processes of dye molecules and antibiotic molecules. Excessive use and discharge of antibiotics, serious pollution of water environment and human health, photochemical reaction through excited state is an effective way of degradation. In this paper, the density functional and time-dependent density functional theory are used to calculate the molecular geometric equilibrium structure, spectral data and frontier molecular orbital data, and to compare the changes of hydrogen bond strength, geometric configuration and electron distribution number in different electronic states. The excited state structure and properties of dye and antibiotic molecules were studied. Firstly, the excited state properties of p-nitrobiphenol-trimethyl Ding Ji amine hydrogen bond complexes were studied by using the CAM-B3LYP hybrid functional group 6-311G (dapp) solvation model. The maximum absorption peak of UV spectrum is 333 nm and the experimental value is 354 nm, which is in good agreement. Compared with the hydrogen bond length, hydrogen bond binding energy and infrared spectrum of different electronic states, the excited state structure is obtained and the formation of N-H is found. The phenomenon of electron-proton transfer observed in the experiment is verified, the electron excitation energy and oscillator intensity are compared, the S1 state is the main excited state, and the frontier molecular orbital is analyzed, which shows that S1 state is an intramolecular charge transfer excited state with 蟺-蟺 * transition characteristic. It provides useful theoretical information for experiments. Secondly, the excited state properties of chlortetracycline-water molecular hydrogen bond complexes were studied by using the B3LYP hybrid functional group 6-311-1 G (dapp) and the CPCM solvation model of water. The maximum absorption peak of UV spectrum is 370 nm and the experimental value is 367 nm, which is in good agreement. By comparing the configuration and vibrational spectra of different electronic states, it is found that in excited states, intramolecular charge transfer is accompanied by intermolecular proton transfer. The results show that the interaction between chlortetracycline and water is enhanced in the excited state, the electron excitation energy and the oscillator intensity are compared, the main excited state is S2 state, and the S1 state and S2 state are both localized excited states, and the frontier molecular orbitals are analyzed. It shows that both S1 and S2 states are intramolecular charge transfer excited states. Finally, the excited state properties of norfloxacin-water molecular hydrogen bond complexes were studied by using the B3LYP hybrid functional group 6-311G (dapp) and the CPCM solvation model of water. The maximum absorption peak of UV spectrum is 277nm and the experimental value is 272nm.The calculated absorption peak of C37N038 is 1734 cm-1 and the experimental value of 1731cm-1 is in good agreement, and the hydrogen bond length and infrared spectra in different electronic states are compared. The results show that the intramolecular hydrogen bond is strengthened in the excited state and the intramolecular hydrogen bond in S _ 4 is stronger than that in S _ 1.Compared with the electron excitation energy and oscillator strength, the main excited states are S _ (1) S _ (2) S _ (2) S _ (4) and S _ (6). By analyzing frontier molecular orbitals and NBOs, it is shown that both S1 and S4 states have 蟺-蟺 * transition characteristics, and S1 states are torsional intramolecular charge transfer excited states.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O644.11

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