理论研究π-镁键复合物的结构和性质

发布时间：2018-05-26 23:23

本文选题：镁键 + 共轭体系　；参考：《吉林大学》2017年硕士论文

【摘要】：本论文应用量子化学计算方法研究了MgX_2(X=H,F)分子分别和乙炔、乙烯、苯环作用并形成复合物时,体系中相互作用的本质。研究结果显示这是一种非共价相互作用,可称之为π-镁键。有趣的是随着参与形成的π电子给体的不同,复合物的结构也发生变化。对于X2Mg···C2H2体系,X2Mg和乙炔分子是共面的,整体结构具有C2v对称性;对于X2Mg···C2H4体系,H2Mg···C2H4和X2Mg···C2H2(X=H,F)体系的结构相似,H2Mg分子和碳碳双键C=C是共面的。但是F2Mg···C2H4二聚体的结构有些不同,由于带负电荷的F原子和C原子之间相互排斥,因此F2Mg分子和碳碳双键C=C不共面;对于X2Mg···C6H6体系,当X2Mg和苯作用的时候,分子更易和苯C-C(C=C)键中心作用,而不是和苯环的面心。在所有复合物的形成过程中,Mg X和C C的键长均增大,并且X Mg X和C C键的拉伸振动发生红移现象。NBO轨道分析显示电荷的转移主要是从共轭分子向MgX_2分子转移,即从C C的成键轨道向Mg的空轨道或Mg-X的反键轨道转移。苯环具有最强的给电子能力,其次是乙烯,乙炔。同时根据结果分析,当配体相同时,Mg F2更容易形成稳定的二聚体复合物。复合物在CCSD(T)水平下计算得到的相互作用能大小在-7.22到-15.80kcal/mol之间。BSSE修正的能量在0.31到1.61kcal/mol之间。能量分解结果显示,静电相互作用和极化作用是稳定复合物的主要作用,分别占总结合能的一半和28%-45%。本文通过和其他含有非传统键的体系对比发现,π-镁键的强度比π-锂键和π-钠键都强,而当Mg F2做路易斯酸配体时,π-镁键与π-铍键强度是相似的。
[Abstract]:In this paper, the nature of interaction between MgX _ 2H _ 2O _ (H) molecules and acetylene, ethylene, benzene rings and their complexes has been studied by means of quantum chemical calculation. The results show that this is a noncovalent interaction, which can be called 蟺-magnesium bond. Interestingly, the structure of the complex changes with the formation of 蟺 electron donors. For X2Mg C2H2 system, the structure of X _ 2mg and acetylene is coplanar, and the whole structure has C2v symmetry, while for X2Mg C2H4 system, the structure is similar to that of C _ 2mg and C _ 2H _ 2H _ 2O _ F), and that of C _ 2mg and C ~ (2 +) C ~ (2 +) is coplanar. However, the structure of the F2Mg C2H4 dimer is somewhat different. Because the negatively charged F atoms and C atoms repel each other, the F2Mg molecule is not coplanar with the carbon-carbon double bond C (C) C; for the X2Mg C6H6 system, when X2Mg and benzene interact, It is easier for the molecule to interact with the benzene-C-C-C bond center than with the benzene ring. During the formation of all the complexes, the bond lengths of mg X and C C increased, and the tensile vibration of X mg X and C C bonds red shifted. NBO orbital analysis showed that the transfer of charge was mainly from conjugate molecules to MgX_2 molecules. That is to say, the transfer from the bonding orbit of C C to the empty orbit of mg or the antibonding orbit of Mg-X. Benzene ring has the strongest electron ability, followed by ethylene and acetylene. According to the results, the stable dimer complex is easier to be formed when the ligands are the same. The interaction energies calculated at CCSD T) level range from -7.22 to -15.80 kcal / mol. The modified energy of BSSE is between 0.31 and 1.61kcal/mol. The results of energy decomposition show that electrostatic interaction and polarization are the main roles of the stable complex, accounting for half of the total binding energy and 28-45% of the total binding energy, respectively. By comparing with other systems containing non-traditional bonds, it is found that the strength of 蟺 -magnesium bond is stronger than that of 蟺 -lithium bond and 蟺 -sodium bond, but when MgF2 is a Lewis acid ligand, the strength of 蟺 -magnesium bond and 蟺 -beryllium bond is similar.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O641.1

【相似文献】