拉曼光谱对具有非重合效应的几种不同类型物质的研究

发布时间：2018-04-10 03:15

本文选题：分子间弱相互作用　切入点：C-H伸缩振动　出处：《浙江理工大学》2017年硕士论文

【摘要】：分子间弱相互作用在生命科学及催化领域起着重要的作用,因此近年来被广泛的研究。对于调查研究溶质结构和溶液环境的变化振动光谱是种灵敏的工具。通过它可以观测振动峰的频率和结构的变化。非重合效应(NCE)是与分子间相互作用有关的重要光谱现象。本论文运用显微拉曼光谱包括基质隔离显微拉曼光谱结合密度泛函理论(DFT)对几种分子的非重合效应进行了研究。通过对氘代丙酮的C=O伸缩振动模、四氢呋喃的C-H伸缩振动模和苯乙酮的C=O伸缩振动模的浓度效应、非重合(NCE)效应和溶剂效应的研究,我们对这些体系中存在的分子间弱相互作用以及分子的聚集结构有新的认识。(1)在文中分别深入的研究了四氢呋喃分子在水溶液及四氯化碳溶液中的C-H伸缩振动模的NCE效应及浓度效应。我们分别采集了THF在水和四氯化碳中从10%到100%浓度的C-H伸缩振动模的各项同性拉曼峰和各向异性拉曼峰。在水溶液中,随着四氢呋喃浓度的增加,我们发现C-H振动模的频率发生红移,NCE效应的值相应地随之增加。然而在四氯化碳溶液中四氢呋喃分子的C-H伸缩振动模在所有浓度下频率保持不变,各项同性与各向异性拉曼峰重合,没有NCE效应。同时,我们用MP2计算四氢呋喃分子的单体及二聚结构来解释以上的振动光谱行为。理论计算可以很好的与实验现象相结合。简而言之,四氢呋喃在水溶液中的强的分子间的相互耦合作用可以很好的解释NCE效应,然而四氢呋喃在四氯化碳溶液中弱的分子间相互耦合作用没有表现出NCE效应。(2)获取了苯乙酮在四氯化碳溶液中不同浓度时的拉曼光谱。对于苯乙酮分子我们发现随着苯乙酮-四氯化碳溶液的稀释,各向同性和各向异性的C=O伸缩振动模的频率发生蓝移,而NCE值随之减小。同时在B3LYP/6-311++G(d,p)计算水平上优化苯乙酮的单体和二聚结构,计算结果可以很好地与实验结果相吻合。(3)为了详细的了解氘代丙酮在四氯化碳中C=O伸缩振动模的NCE效应,我们获取了体积分数从30%到100%的氘代丙酮显微拉曼光谱以及它的偏振显微拉曼光谱。随着浓度的增加C=O峰频率发生红移。随着溶液的稀释,NCE的值随着减小。同时收集了低温氩气基质隔离中的氘代丙酮的显微拉曼光谱,观察到在8 K时氘代丙酮C=O伸缩谱带是一个尖锐的单峰,25K时分裂成两个小峰。同时我们利用Gaussian09在MP2/6-311++G(d,p)计算水平上优化氘代丙酮单体和二聚结构,计算表明氘代丙酮分子通过分子间相互作用分别可以形成头对尾平行的二聚结构,这种二聚结构可以很好地解释氘代丙酮C=O振动模的NCE效应。
[Abstract]:Weak intermolecular interaction plays an important role in life sciences and catalysis, so it has been widely studied in recent years.It is a sensitive tool for investigating the variation of solute structure and solution environment.The frequency and structure of the vibration peak can be observed by it.Noncoincidence effect (NCE) is an important spectral phenomenon related to intermolecular interaction.In this paper, the noncoincidence effects of several molecules have been studied by means of micro-Raman spectroscopy, including matrix isolated micro-Raman spectroscopy and density functional theory (DFT).The concentration effect, noncoincidence NCE-effect and solvent effect of C-H stretching vibration modes of deuterated acetone, C-H stretching vibration modes of tetrahydrofuran and acetophenone are studied.We have a new understanding of the weak intermolecular interaction and the molecular aggregation structure in these systems. (1) the C-H stretching vibration modes of tetrahydrofuran molecules in aqueous solution and carbon tetrachloride solution have been studied in this paper.NCE effect and concentration effect.We have collected the isotropic and anisotropic Raman peaks of C-H stretching vibrational modes of THF in water and carbon tetrachloride from 10% to 100% respectively.With the increase of tetrahydrofuran concentration in aqueous solution, we find that the frequency of C-H vibrational mode increases with the red shift NCE effect.However, in the solution of carbon tetrachloride, the C-H stretching vibrational modes of tetrahydrofuran remain constant at all concentrations, and the isotropic and anisotropic Raman peaks coincide with each other, and there is no NCE effect.At the same time, we use MP2 to calculate the monomer and dimer structure of tetrahydrofuran molecule to explain the above vibrational spectrum behavior.Theoretical calculation can be well combined with experimental phenomena.In short, the strong intermolecular coupling of tetrahydrofuran in aqueous solution can explain the NCE effect well.However, the weak intermolecular coupling of tetrahydrofuran in carbon tetrachloride solution does not show the NCE effect.) Raman spectra of acetophenone in different concentrations of acetophenone in carbon tetrachloride solution were obtained.For acetophenone molecules we find that with the dilution of acetone-carbon tetrachloride solution the frequency of isotropic and anisotropic Con O stretching vibrational modes is blue shifted and the NCE value decreases.At the same time, the monomer and dimer structures of acetophenone were optimized at the level of B3LYP/6-311 GDX. The calculated results were in good agreement with the experimental results. (3) in order to understand the NCE effect of deuterated acetone in CCO stretching vibration mode in carbon tetrachloride in detail,The microscopic Raman spectra of deuterated acetone from 30% to 100% in volume fraction and its polarization microRaman spectra were obtained.With the increase of concentration, the frequency of Con O peak shifts red.The value of NCE decreases with the dilution of the solution.The microRaman spectra of deuterated acetone isolated in low temperature argon substrate were also collected. It was observed that the C-O stretching band of deuterated acetone at 8 K was a sharp single peak and split into two small peaks at 25 K.At the same time, we optimize the deuteriated acetone monomer and dimer structure at the level of MP2/6-311 MP2/6-311 by using Gaussian09. The results show that the deuteriated acetone molecules can form a head to tail parallel dimer structure by intermolecular interaction.The dimeric structure can explain the NCE effect of the vibrational mode of deuterated acetone.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O657.37

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