【作者】 刘丽；

【导师】 章福平； 毕树平；

【作者基本信息】 南京大学 ， 化学工程（专业学位）， 2018， 硕士

【摘要】 气相（H₂O）₆团簇的研究对于理解液相和固相本体水的性质、揭示大气物理与化学及生命科学领域的本质问题具有重要意义,对不断变化与错综复杂的氢键网络重排动力学过程的理解是至关重要的核心问题。自Richardson等报道了在（H₂O）₆的Prism构型中存在两根氢键协同断裂的现象后,对于水团簇氢键网络重排又引起了广泛的关注。氢键网络重排动力学机制和完整的反应路径对于理解重排过程和将重排机制拓展到其它水团簇中有重要意义,但目前从分子水平上提供相关两根氢键协同断裂的详细过程未见报道。在Al（H₂O）₆³⁺水溶液体系模拟研究中,需添加真实溶剂水分子来模拟短程的溶剂效应。但由于真实溶剂水分子数目和排布方式带来的大量局域最小点的问题,在添加真实溶剂水分子问题上一直缺乏普遍适用的方法。手性物质广泛存在于环境和生物体中,Al（III）与有机配体分子以1:2或1:3的方式配位可形成不同的手性配合物。从分子水平上提供手性配合物的静态结构和动态水交换反应的相关信息对于理解手性物质理化性质的相似性和手性对映性有重要意义。本论文围绕上述问题开展了研究工作,论文共分为四章:1.（H₂O）₆氢键网络“协同断裂和分步形成”重排机制的MP2—团簇方法研究。采用二阶微扰理论（Moller-Plesset second order perturbation theory,MP2）结合团簇模型（Cluster model,CM）,在aug-cc-pVDZ基组下,模拟了（H₂O）₆的Prism构型中氢键“协同断裂和分步形成”的动力学反应过程。其它三种典型物种包括手性异构体、（D20）6和（H2180）6也进行了研究。首次提出了两根氢键协同断裂并形成一根氢键（“-2+1”）和另一根氢键后形成（“+1”）的两步连续氢键网络重排机制,其中“-2+1”过程为决速步骤。整个氢键重排涉及一个bifurcation结合两个flip形式的隧穿过程,对应的置换反演表达式为P =（AD）（B F）（C E）（1 8 2 7）（3 11）（4 12）（5 9）（6 10）。采用 CCSD（T）/aug-cc-pVDZ 计算活化单点能AEelec,a≠与文献报道的随最小路径变化的势能（Potentialenergy along the minimum-energy paths,V）吻合。其它8种与重排相关的可能的转动方式的计算结果均表明,geared路径为最可行路径,其次是antigeared路径。2.Al（H₂O）₆³⁺水交换反应溶剂效应的密度泛函理论研究—外层真实溶剂水分子数目和排布方式。采用密度泛函理论（Density functional theory,DFT）与团簇模型（Cluster model,CM）结合的量子化学计算方法研究Al（H₂O）₆³⁺水交换反应溶剂效应中外层（第二水化层）真实溶剂水分子数目和排布方式。在B3LYP/6-311+G（d,p）基组水平下,采用逐个添加水分子直至内层氢键饱和的方法,得到了外层真实溶剂水分子数目（Nm’）为1～7时的最佳排布方式,探索了一种简单有效的外层水分子数目和排布方式的研究方法。通过对比逐个添加法和独立添加法中Nm’对水交换反应路径中反应物种的结构参数、能量参数和过渡态寿命的影响,确认Al（H₂O）₆³⁺水交换反应中Nm’ = 6为最佳的外层溶剂分子数。3.铝-草酸和铝-麦芽酚手性配合物特性的密度泛函理论研究。采用密度泛函理论（Density functional theory,DFT）结合团簇模型（Cluster model,CM）和极化连续模型（Polarizable Continuum Model,PCM）的量子化学计算方法,在 B3LYP/6-311+G（d,p）基组水平下,以铝-草酸和铝-麦芽酚为典型实例,研究手性铝有机配合物的动静态性质,系统地开展了以下工作:（1）采用GP-SM-PCM模型优化得到了 1对铝-草酸和3对铝-麦芽酚手性配合物,并通过静态结构参数、能量参数和谱学性质分析了手性配合物之间的差异;（2）采用GP-SM（PCM）模型模拟了手性配合物可能存在的10条水交换反应路径,对比了手性配合物水交换反应速率常数;（3）采用GP-SM（PCM）模型通过Berny方法得到了铝-草酸手性配合物异构体构型转化的动态反应路径,并计算了构型转化的活化能。4.铝-草酸1:3手性配合物特性的密度泛函理论研究。采用密度泛函理论（Density functional theory,DFT）结合团簇模型（Cluster model,CM）和极化连续模型（Polarizable Continuum Model,PCM）的量子化学计算方法,在B3LYP/6-311+G（d,p）基组水平下,优化得到一对Al（Ox）33-手性异构体的静态构型,并对比分析了手性异构体的静态结构特性、能量参数、NMR谱图、IR光谱和VCD光谱特性以及前线分子轨道和静电势特征。结果表明:手性异构体结构和能量参数及NMR化学位移相近,IR谱图基本重合而VCD谱上下对映,但前线分子轨道不完全对映。计算结果体现了 Al（ox）₃^3-手性异构体理化性质的相同性和微观结构的差异性。更多还原

【Abstract】 Study on（H₂O）₆ in gas phase has important significance for understanding the properties of water in liquid and solid phase,as well as uncovering the essential problems in the field of atmospheric physics and chemistry and life science.The insight of the rearrangement dynamics of the ever-changing and complex hydrogen-bond networks is the core issue for these studies.Recently,Richardson et al reported a new phenomenon of concerted breaking of two hydrogen-bonds in water hexamer prism.This research has caused widespread concern.The dynamic mechanism and the whole reaction pathways of the rearrangement of hydrogen-bond networks are important to understand the rearrangement process and to investigate other water clusters.However,the detailed process of the concerted breaking of two hydrogen-bonds at molecular level has not been reported.In the simulation of Al（H₂O）₆³⁺aqueous solution system,the explicit water molecules are added to simulate the short-range solvent effect.However,due to the large number of local minimum structures caused by the number and arrangement of the explicit water molecules,there is no uniform method for adding the explicit water molecules.Chiral substances are widely exist in environment and living organisms.The coordination of Al（Ⅲ）and organic ligand molecules in the way of 1:2 or 1:3 can form different chiral complexes.At the molecular level,the information about the static structure and dynamic water exchange reaction of chiral complexes is important for understanding the similarity and chiral enantiomers of chiral compounds.In this dissertation,the key issues mentioned above are investigated.There are four chapters as follows:1.MP2-CM studies on the mechanism of the "Concerted breaking and stepwise making" rearrangement of hydrogen-bond networks in water hexamer.The "concerted breaking and stepwise making" dynamic reaction pathways for the rearrangement of hydrogen-bond networks in water hexamer prism are simulated by M（?）ller-Plesset second order perturbation theory（MP2）combined with cluster model（CM）at aug-cc-pVDZ level.Other three typical species including the chiral isomer of（H₂O）₆,（D2O）6 as well as（H218O）6 are also investigated.For the first time,the pathways for concerted hydrogen-bonds breaking reactions of a two-step mechanism are obtained.The first step is the concerted breaking of two hydrogen-bonds and making of one of the hydrogen-bonds,denoted as "-2+1" process,which is the rate-determining step.The second step is the making of another hydrogen-bond,denoted as "＋1 "process.The whole reaction pathways combine a bifurcation with a double flip,corresponding to the permutation P =（A D）（B F）（C E）（1 8 2 7）（3 11）（4 12）（5 9）（610）.The activation single-point energy calculated by CCSD（T）/aug-cc-pVDZ agrees well with the previous report.All the results of other eight possible rotation modes related to the rearrangement prove that the geared pathway of "-2+1"/"+1" processes is the most feasible pathway,and then,antigeared pathway is also feasible.2.Density functional theory studies on the solvent effects in Al（H₂O）₆³⁺Water-exchange reactions-The number and arrangement of outer-sphere water molecules.Density functional theory（DFT）calculations combined with cluster model（CM）are performed at B3LYP/6-311+G（d,p）level for investigating the solvent effects in Al（H₂O）₆³⁺ water-exchange reactions.The "One-by-one" method is proposed to obtain the most representative number and arrangement of explicit H₂O in the second hydration sphere.First,all the possible ways to locate one explicit H₂O in second sphere（Nm’ = 1）based on the gas phase structure（Nm’=0）are examined,and the optimal pathway（with the lowest energy barrier）for Nm’ = 1 is determined.Next,more explicit H₂O are added one by one until the inner-sphere is fully hydrogen bonded.The optimal pathways with Nm’ = 0～7 are obtained finally.The structural and energetic parameters as well as the lifetimes of transition states are compared with the results obtained with "Independent-minimum" method and "Independent-average" method,and all three methods show that the pathway with Nm’ = 6 may be representative.Our results give a new idea for finding the representative pathway for water-exchange reactions in other hydrated metal ion systems.3.Density functional theory studies on the properties of aluminium-oxalate and aluminium-maltolate chiral complexes.Density functional theory（DFT）calculations combined with cluster model（CM）are performed at B3LYP/6-311+G（d,p）level for investigating the aluminium-organic chiral complexes.Using both aluminium-oxalate and aluminium-maltolate complexes as examples,systematic studies on the static and dynamic properties of chiral aluminium-organic complexes are conducted:（1）The static configurations for one pair of aluminium-oxalate and three pairs of aluminium-maltolate chiral complexes are optimized to obtain their static structure parameters and energetic parameters,as well as spectroscopic properties,based on the gas phase-supermolecule-polarizable continuum model（GP-SM-PCM）;（2）Ten possible water-exchange reaction pathways are obtained with GP-SM（PCM）model,and the water-exchange rate constants are predicted;（3）The chirality inversion pathway for aluminium-oxalate is simulated with GP-SM（PCM）model using Berny algorithm,and the activation barrier is obtained.4.Investigation of the properties of chiral tris-oxalate-Al（Ⅲ）complexes by the density functional theory.Density functional theory（DFT）combined with the cluster model（CM）and the polarizable continuum model（PCM）at the level of B3LYP/6-311+G（d,p）are used to obtain the static configurations of chiral tris-oxalate-Al（Ⅲ）(Al（ox）₃^3-).The structural and energetic parameters,NMR,IR and VCD spectroscopy,frontier molecular orbitals and electrostatic potential characteristics of the chiral isomers are compared.The results show that the structural and energetic parameters as well as the NMR shifts are basically the same.The IR of chiral Al（ox）₃^3-is the same but their VCD are basically equal in intensity but opposite in sign（mirror images of each other）.However,there are obvious differences in the frontier molecular orbitals.The results give insight into the similarity in physicochemical properties and the enantiomeric characteristics on the Licrostructure of the chiral Al（ox）₃^3-.更多还原