【作者】 冯璐；

【导师】 张红星；

【作者基本信息】 吉林大学 ， 物理化学， 2011， 博士

【摘要】 双氢键是氢键的一种,特殊之处在于其非传统的质子受体,一个带有负电荷的氢原子。一些双氢键的强度与常规氢键的强度相当,这使得双氢键能够影响物质的结构、相关体系的反应性及选择性,因而在催化反应、晶体工程以及储氢材料等领域具有潜在的应用价值。本论文针对这种特殊的氢键作用,采用多种理论研究方法对含有H…H作用的复合物体系的性质及其本质进行了详细地研究。论文中所研究的构型和分析结果将有助于加深对双氢键本质的了解。主要内容包括以下五个方面:（1）在MP2/6-311++G（d,p）水平下对C₂H_4-nCl_n…MgH₂（n = 0,1,2,3）体系进行了研究。根据优化的结构该体系可分为三组:L构型只包含CH…H作用,相互作用能在0.5 2.0 kcal/mol的范围;F和S构型表示体系呈五元环和六元环构型,其同时包含了CH…H和HMg…Cl作用,相互作用能在3.4 5.9 kcal/mol左右。所有复合物体系内的质子供体C–H键长较单体时明显变长,并伴随C–H伸缩振动的红移现象。乙烯分子上Cl原子取代数目的增加,对H…H作用体系的几何结构、频率、相互作用能以及C–H的σ*反键轨道电子占据数都产生了重要影响。采用分子中原子理论（AIM）和自然键轨道理论（NBO）方法对C₂H_4-nCl_n…MgH₂（n = 0,1,2,3）体系进行了分析,通过对比几何结构数据以及AIM拓扑数据,考察了环状结构对双氢键体系的影响。利用NBO分析解释了其中的环状结构内存在的与常规氢键相反的电荷转移方向。研究中所发现的新连接形式（六元和五元环状构型）将有助于加深对双氢键本质的了解。（2）采用从头算MP2方法,在aug-cc-PVTZ基组水平上对由CH₄,C₂H₄,C₂H₂以及其氯代衍生物和MgH₂分子形成的C–H…H作用体系进行了研究。研究了它们的几何结构、伸缩振动频率和相互作用能等性质。结果表明双氢键的强度按照如下质子供体顺序递增:C（sp³）–H < C（sp²）–H< C（sp）–H。对于含有相同C原子杂化类型的复合物体系,Cl原子取代数目增加增强了C–H…H作用强度。对于大部分环状结构,质子受体Mg?H键的键长变化以及频率变化都明显大于质子供体C–H键的相应变化值。NBO分析表明环状结构中除H…H作用以外同时具有的Mg…Cl作用引起了额外的电荷转移,使得总的电荷转移方向不同于传统氢键中的结果。AIM分析考察了H…H键临界点处的电子密度拓扑性质,结果突出了C–H…H双氢键的静电作用本质。（3）在MP2/6-311++G（d,p）水平下对C₂H_4-nCl_n…NaH（n = 0,1,2,3）体系进行了详细的理论研究。根据优化出的几何构型将C₂H_4-nCl_n…NaH体系分为三组进行讨论:L构型只包含CH…H作用;F和S代表同时包含了CH…H和HNa…Cl作用的五元和六元环构型。分析了复合物结构、相互作用能、电子密度拓扑数据与H…H作用距离之间的关系。AIM分析证明了C₂H_4-nCl_n…NaH体系中H…H作用的静电作用本质,同时根据反映键强度的电子密度ρ值进一步分析环状构型对H…H作用的影响。通过NBO分析综合考虑了C-H和H-Na键的σ成键轨道和σ*反键轨道上电子占据数变化对键长的影响,并进一步分析了分子间独特的双通道电荷转移特征。（4）在MP2/6-311++G（d,p）水平下对MH…HC₂Cl₃ （M=Li, Na, K）体系进行了细致的研究。L构型只包含CH…H作用;F和S构型代表包含了CH…H和HM…Cl作用的五元和六元环构型。分析了质子供体分子相同的情况下,不同的质子受体分子对体系双氢键的影响。质子受体分子电负性按照Li、Na、K规律递减,而相同构型下的MH…HC₂Cl₃复合物体系的H…H距离、相互作用能、电荷转移大小、电子密度拓扑性质等随该电负性顺序发生了递减或递增的变化。同时运用AIM分析和NBO分析对复合物体系双氢键的性质进行了讨论,进一步分析了分子间独特的电荷转移特征。（5）采用密度泛函B3LYP方法以及6-31++G（d,p）和6-311++G（3df,2p）基组,研究了CaH₂…HY（Y = C₂H, C₂HCl, HC₂BeH,CN, NC）体系的几何结构、双氢键的相互作用能和电子密度拓扑性质等。从优化所得的CaH₂…HY体系结构来看,B3LYP/6-31++G（d,p）方法计算所得体系中的CaH₂分子呈线型结构,而B3LYP/6-311++G（3df,2p）方法优化得到了一个非常明显的弯曲结构。基于不同的CaH₂分子结构,两种方法计算得到的CaH₂…HY体系H…H间距离、相互作用能以及分子间电荷转移量等结果非常接近。结果表明CaH₂分子结构的差异性对CaH₂…HY体系双氢键的性质影响微乎其微。通过NBO分析考察了Ca-H和H-Y片段的轨道间相互作用以及不同基组水平下的CaH₂分子电子结构特征的不同。另外,采用分子中的原子（AIM）方法分别对各复合物体系中相关键临界点处的电子密度拓扑性质进行了分析,结果证明了CaH₂…HY体系中H…H相互作用的静电作用本质。更多还原

【Abstract】 Dihydrogen bonding is an unconventional hydrogen bonding. It has strength and directionality comparable with those found in classical hydrogen bonding. Consequently, it can influence structure, reactivity and selectivity in solution and solid state, finding thus potential utilities in catalysis, crystal engineering, and materials chemistry. The theoretical studies were performed on the structures, interactions and properties of some representative systems containing dihydrogen bond and other interactions in this thesis. The results obtained on new structures and intermolecular interactions may be valuable for improving our understanding of the nature of intermolecular interaction, and enriching our knowledge of dihydrogen bonds and other weak intermolecular interactions.There are five main aspects included in this thesis:（1） The dihydrogen-bonded complexes of ethylene and its chlorine derivatives with magnesium hydride have been systematically investigated at the MP2/6-311++G（d,p） level. The studied complexes are divided into three groups based on the optimized structures. The most stable complexes with interaction energies between 3.4 and 5.9 kcal/mol present circular structures enclosed by CH…H and HMg…Cl bonds. The other linear structures with interaction energies between 0.5 and 2.0 kcal/mol are stabilized by only CH…H dihydrogen bond. All investigated complexes exhibit slight elongation of C–H bond accompanied by a red shift of C–H stretching frequency. With increasing chlorine atoms on ethylene, the geometries, frequencies, interaction energies, and the electron density in the C–Hσ* antibonding orbital of the complexes all increase or decrease gradually. The nature of the electrostatic interaction in this type of dihydrogen bond has also been unveiled by means of the atoms in molecules （AIM） and natural bond orbital （NBO） analysis. The effect of ring structures on the dihydrogen bonding systems has been considered by comparing the geometric data and AIM parameters. Moreover, the calculated direction of net charge transfer of ring structure complexes is contrary to the previous found in dihydrogen bonded systems.（2） The C–H…H dihydrogen-bonded complexes of methane, ethylene, acetylene, and their derivatives with magnesium hydride have been systematically investigated at the MP2/aug-cc-PVTZ level. The results confirm that the strength of dihydrogen bonding increases in the following order of proton donors: C（sp³）–H < C（sp²）–H< C（sp）–H and chlorine substituents enhance the C–H…H interaction. For the majority complexes with cyclic type of structure, the bond length variations and red-shifts of Mg-H proton-accepting bond are more sensitive than the corresponding value of C-H proton-donating bond. The nature of the electrostatic interaction in these C–H…H dihydrogen bond has also been unveiled by means of the atoms in molecules （AIM） analysis. The natural bond orbital （NBO） analysis suggests that the charge transfer in cyclic complexes have dual-channel character. The direction of net charge transfer of cyclic complexes is contrary to the previous found in dihydrogen bonded systems.（3） The dihydrogen-bonded complexes of ethylene and its chlorine derivatives with sodium hydride have been systematically investigated at the MP2/6-311++G（d,p） level. The studied complexes are divided into three groups （including Linear, Five- and Six-membered cyclic structures） based on the optimized structures. The structural, energetic and topological parameters are presented and analyzed in terms of their possible correlation with the interaction energies and the intermolecular H…H distances. The nature of the electrostatic interaction in this type of dihydrogen bond has also been unveiled by means of the atoms in molecules （AIM） and natural bond orbital （NBO） analysis. The effect of ring structure on the dihydrogen bonding systems has been considered by comparing to corresponding linear structure. NBO analysis suggests that the EDT in cyclic structures have dual-channel character.（4） The properties of the dihydrogen-bonded （DHB） complexes MH…HC2Cl3 （M=Li, Na, K） were calculated by the MP2/6-311++G（d,p） method. The studied complexes are divided into three groups （including Linear, Five- and Six-membered cyclic structures） based on the optimized structures. For the same optimized structure, if the acceptors listed in order of increasing proton-accepting ability are LiH < NaH < KH. It is undoubted that such observations are related with the gradually decreasing of electronegativity for Li, Na and K. The nature of the electrostatic interaction in this type of dihydrogen bond has also been unveiled by means of the atoms in molecules （AIM） and natural bond orbital （NBO） analysis. The effect of ring structure on the dihydrogen bonding systems has been considered by comparing to corresponding linear structure.（5） The B3LYP/6-31++G（d,p） and B3LYP/6-311++G（3df,2p） calculations are carried out to investigate the structures and properties of dihydrogen-bonded CaH₂…HY （Y = C₂H, C₂Cl, C₂BeH,CN, and NC） complexes. Our calculations revealed two possible structures for CaH₂ in CaH₂…HY complexes: linear （I） and bent （II）. The bond lengths, interaction energies, and strength for H…H interactions obtained by both B3LYP/6-31++G（d,p） and B3LYP/6-311++G（3df, 2p） methods are quite close to each other. The inverse ratio correlation indicates interaction energy decrease with the increase of the electron density at Ca–H bond critical point. The AIM results point out that for all of Ca–H…H–Y interactions considered here the Laplacian of the electron density at H…H bond critical point are positive indicating the electrostatic nature in these Ca–H…H–Y dihydrogen bond systems.更多还原