【作者】 于丹；

【导师】 刘靖尧；

【作者基本信息】 吉林大学 ， 物理化学， 2021， 博士

【摘要】 由于弱相互作用在多种研究领域中的重要应用,其相关体系的结构、作用本质及性质分析一直受到广泛关注。本文从理论上详细考察了电子给体分别包含未成对电子、π电子及孤对电子的三类弱相互作用体系,并针对体系的几何结构、性质及相互作用本质做了系统的研究。本文中,首先提出一种新型弱相互作用类型,即单电子镁键;并对一个共轭分子与多个路易斯酸分子作用所形成的多体π-铍键和π-镁键复合物体系进行了详细的研究;最后在之前研究的基础上,考察了超碱金属阳离子Li₃⁺束缚多个N₂配体的非共价相互作用体系。本文具体研究内容如下:1、用量子化学计算方法对Mg X₂（X=F,H）分子与自由基Y[Y=CH₃,CH₂CH₃,CH（CH₃）₂和C（CH₃）₃]相互作用形成的复合物进行了表征。所有体系中的分子间结合距离都小于Mg和C的范德华半径之和,表明它们之间形成了非共价相互作用,即单电子镁键。能量分解分析表明,静电和极化贡献是稳定复合物的主要因素。对相互作用能,分子中的原子和独立梯度模型分析的研究结果表明,电子给体Y上的甲基取代对其与Mg X₂的结合有积极的影响。与其他非成键相互作用相比,单电子镁键的作用强度与单电子铍键和π-镁键相当。2、为了揭示π-共轭体系与Lewis酸分子之间相互作用位点的多样性及不同Lewis碱的给电子能力,我们研究了四种路易斯酸和三种路易斯碱相互作用形成的复合物n X₂M···Y[n=1,2,3,4;X=F,H;M=Be,Mg;Y=C₂H₂,C₂H₄,C₆H₆],详细考察复合物的几何结构和相关性质。根据Lewis碱的不同（乙炔、乙烯、苯）,将优化后的构型分为三大类。研究结果表明乙炔比乙烯和苯具有更好的给电子性能,并且只有乙炔分子可以与三个独立的Be H₂/Be F₂分子相互作用。RDG函数分析结果显示,对于所有的多体复合物,都存在路易斯酸碱之间的相互作用。此外,通过将3X₂M···C₆H₆复合物同分异构体间的相互作用能结果进行对比,发现两个路易斯酸分子的最优相对位置是对位。NBO结果表明,复合物n X₂M···Y主要的分子间电荷转移来自共轭分子的π_CC成键轨道到Be原子的2p空轨道或Mg原子的3p轨道的轨道相互作用。AIM分析是描述各种成键特征的有效手段,其结果表明,在研究的π-铍键、π-镁键复合物中,各组分间主要是通过环路径（RP）和键路径（BP）相互作用的。3、在MP2/6-311+G（d）水平上,对超碱阳离子Li₃⁺捕集N₂的潜力及其在气态氮中的行为进行了理论研究。复合物Li₃⁺（N₂）_n（n=1-7）结构的演变及其稳定性表明,N₂分子倾向于与Li₃⁺核的不同顶点结合,并且Li₃⁺在第一个配位壳层中可能有捕获多达12个氮分子的能力。根据自然布局和分子轨道分析,Li₃⁺在Li₃⁺（N₂）_n（n=1-4）复合物的最低能量结构中保持其超原子特性。通过计算Li₃⁺（N₂）_n（n=1-4）体系各种可能的解离通道的吉布斯自由能,发现Li₃⁺在（N₂）_n团簇中具有热力学稳定性。与以静电作用为主的Li₃⁺（H₂O）_n的情况不同,静电和极化相互作用对复合物Li₃⁺（N₂）_n形成的贡献相当。此外,Li₃⁺与N₂的结合能大于Na⁺和K⁺离子对N₂的吸附能,说明超碱阳离子Li₃⁺对N₂分子的吸附能力强于重碱金属离子。更多还原

【Abstract】 Due to the extensive application of weak interaction in many research fields,the structures,properties,and nature of the interaction of related systems have been paid much attention.In this paper,three types of weak interactions where radicals,conjugated molecules,and lone pair serve as electron donors,respectively,have been studied in detail by quantum chemical methods.The geometrical structure,properties and interaction nature of the resulting system have been systematically examined.In this thesis,a new type of weak interaction,namely single-electron magnesium bond,has been proposed.And then,multibody complexes formed between a conjugated molecule and multiple magnesium/beryllium salt molecules have been studied in detailed.Besides,the non-covalent interaction system of superalkali metal cation Li₃⁺binding multiple N₂ligands has been investigated.The main contributions of this thesis are as follows:1.The complexes formed between Mg X₂（X=F,H）molecules and alkyl radicals Y[Y=CH₃,CH₂CH₃,CH（CH₃）₂,and C（CH₃）₃]have been characterized by using quantum chemical methods.The binding distances in all cases are shorter than the sum of vd W radii of Mg and C,indicating the formation of a non-covalent interaction,namely single-electron magnesium bond.Energy decomposition analysis reveals that electrostatic and polarization contributions are the major components responsible for the stability of the studied complexes.According to interaction energy,atoms in molecules,and independent gradient model analyses,methyl substitution on electron donor Y imposes a positive effect on its complexation with Mg X₂.When compared with other nonbonded interactions,single-electron magnesium bond is found to have strength comparable to those of single-electron beryllium bond andπ-magnesium bond.2.To reveal the diversity of interaction sites betweenπ-conjugated and Lewis acid molecules and compare the electron-donating ability of different Lewis bases,we have studied the geometric structures and related properties of the n X₂M···Y[n=1,2,3,4;X=F,H;M=Be,Mg;Y=C₂H₂,C₂H₄,C₆H₆]complexes.Results indicate that acetylene possesses better electron-donating performance than ethylene and benzene.And only the C₂H₂molecule can bind with three independence Be H₂/Be F₂molecules.The RDG results indicate that there is intermolecular interactions between each Lewis acid and Lewis base molecule in all cases.The results of interaction energy of the3X₂M···C₆H₆complexes show that para-position is the preferred relative location of two Lewis acid subunits.NBO analysis reveals that the main charge-transfer arises from theπ_CCbonding orbital of the conjugated molecule to the empty 2p orbital of Be atom or 3p orbital of Mg atom.AIM analysis,which serves as an effective method to describe bonding character,has revealed that the MX₂and Y subunits are mainly connected by ring path（RP）and bond path（BP）in the studiedπ-Be andπ-Mg complexes.3.The potential of superalkali cation Li₃⁺for capturing N₂and its behavior in gaseous nitrogen have been theoretically studied at the MP2/6-311+G（d）level.Evolution of structures and stability of the Li₃⁺（N₂）_n（n=1-7）complexes shows that the N₂molecules tend to bind to different vertices of the Li₃⁺core,and that Li₃⁺might have the capacity to capture up to twelve nitrogen molecules in the first coordination shell.Based on natural population and molecular orbital analyses,Li₃⁺keeps superatom identity in the lowest-lying Li₃⁺（N₂）_n（n=1-4）complexes.The change in Gibbs free energies of possible fragmentation channels also indicates thermodynamic stability of Li₃⁺in the（N₂）_nclusters when n≤4.Different from the case of Li₃⁺（H₂O）_nwhere the electrostatic interaction is dominant,the electrostatic and polarization components are found to make nearly equal contributions to the Li₃⁺（N₂）_ncomplex formation.In addition,it can be concluded that superalkali cation Li₃⁺surpasses heavy alkali metal cations in capturing N₂molecules since it has larger binding energy with N₂than Na⁺and K⁺ions.更多还原