【作者】 侯娜；

【导师】 吴迪；

【作者基本信息】 吉林大学 ， 物理化学， 2014， 博士

【摘要】 团簇是当今化学比较活跃的研究领域，也是无机化学、材料化学等领域的研究热点，其在固体、表面物理、分子物理以及催化等方面也有重要作用。在团簇化学发展的过程中，人们发现某些特定尺寸和组分的团簇可以模拟元素周期表中单个原子的性质，这类原子团簇被描述为“超原子(Superatoms)”。超碱金属是超原子的一个重要分支，由于原子簇的聚集效应，超碱金属团簇通常具有比碱金属原子还低的电离势(IP)。本文从理论上考察了两类超碱金属体系，并对体系的几何结构、电子结构、成键特征等性质进行了详细的研究；此外还考察了超碱金属与有机配体构成的复合物体系，主要对其非线性光学性质进行了理论研究；并对超原子Al14团簇与水分子的反应进行了研究。主要贡献如下：1.首次预测了用氢原子作为配体构造超碱金属阳离子体系M2H2n+1+(M=F,O, N, C)。在OVGF/6-311++G(3df,3pd)水平下，计算得到了这些非金属阳离子的很低的电子亲和势(EA)3.55–4.48eV，因此它们可以归类于超碱金属阳离子。从键长可知，F2H3+和O2H5+阳离子可以分别表示为(HF)H+(FH)和(H2O)H+(H2O)，包含强的对称氢键。同时，值得注意的是，包含传统氢键的N2H7+体系可以看作是由NH4+和NH3单元两部分组成，而C2H9+中弱的范德华相互作用使CH5+和CH4两个单元结合在一起。此外，根据正的解离能，M2H2n+1+阳离子很稳定不易解离出一个H+离子或者一个MHn分子。这个工作确定H原子可以作为配体设计超碱金属，为超碱金属家族引入了非金属成员。2.基于具有独特电子结构的超碱土金属团簇，我们理论设计了低电子亲和势的一类超原子复合物(M F)+(M=OLi4, NLi5, CLi6, BLi7和Al14)。超原子M和F之间具有很强的相互作用，复合物表现出相当大的HOMO LUMO能隙值及高解离能，说明这些超原子体系具有很好的稳定性。需要特殊指出的是，氟化作用对降低M+的VEA值起着重要的作用，低的VEA值使(M F)+氟化物可以归类于超碱金属家族。(M X)+(X=F, Cl和Br)体系的垂直电子亲和势，与卤素原子自身的亲和势没有直接关系，而与它的电负性相关。卤化作用对降低超碱土金属团簇的垂直电子亲和势值有积极的作用，这为新型超碱金属的设计提供了新的思路。3.采用密度泛函(DFT)理论对超碱金属电子化物Li3@calix[4]pyrrole和Li3O@calix[4]pyrrole的几何结构，相对稳定性和非线性光学性质进行了理论研究。通过与Li@calix[4]pyrrole比较发现，以超碱金属Li3和Li3O为电子供体可以给体系带来更大的非线性光学响应。此外,当Li3和Li3O分子平面与calix[4]pyrrole配体的四个N原子构成的平面平行作用时，超碱金属的电离程度更高，体系具有更大的一阶超极化率值。我们的工作为合成新型的基于超原子的非线性光学材料提供了理论指导。4. Al14团簇具有类似超碱土金属的特性，使用密度泛函理论B3LYP方法对Al14团簇与水分子的反应机理进行了研究。研究表明Al14团簇化学吸附水分子，并形成Al–O键。Al–O键相邻的Al原子可以作为路易斯碱位点，接受一个H原子，导致O–H键断裂，形成HAl14(OH)中间体。此外Al14团簇还可以与更多的水分子反应，甚至可以生成氢气。超碱土金属Al14依次吸附解离三个水分子及生成第一个H2分子的反应过程是放热的，反应后Al14单元的结构基本保持完整性。但是HAl14(OH)3中间体表面吸附解离第四个水分子之后，Al14单元的结构发生扭曲并且改变了其最初的构型。我们预测超原子可以催化水分子制取氢气，这为氢气的制备有一定的理论指导作用。更多还原

【Abstract】 Clusters are of considerable interest in research on inorganic chemistry andmaterials chemistry, and play an important role in solid, surface physics, molecularphysics, catalysis and other fields. In preliminary work, Khanna and Jena haveproposed that atomic clusters with suitable size and composition could mimic thechemical behavior of atoms in the periodic table. Such intriguing species are, hence,termed as “superatoms”. A well-known subset of superatoms is superalkali, which arecharacterized by lower ionization potentials than those of alkali-metal atoms.In this thesis, two new kinds of superalkali cations are investigated by thequantum chemical method. Their structures, bonding features and other properties arediscusses in detail. We have discussed nonlinear optical properties of the(super)alkali-doped compounds by means of density functional theory. In addition, themechanism of the reaction between Al14cluster and H2O molecules has been studied.The main contributions are as follows:1. A new type of hydrogen-based M2H2n+1+(M=F, O, N, C) superalkali cationshas been theoretically predicted at the CCSD(T)/6-311++G(3df,3pd) level. Thesenonmetallic cations exhibit low vertical electron affinities of3.55–4.48eV at theOVGF/6-311++G(3df,3pd) level, and hence should be classified as superalkali cations.It is also worth mentioning that the weakly bound N2H7+and C2H9+cations exhibiteven lower VEA values than the ionization potential (IP) of Cs atom. In addition,according to the positive dissociation energies, the M2H2n+1+cations are stable withrespect to loss of an H+ion or an MHnmolecule. Our results presented in this worknot only verify the feasibility of utilizing hydrogen atoms as ligands in designingspecial superalkalies but add non-metallic candidates to the superalkali family.2. A new kind of cationic superatom compounds (M-F)+(M=OLi4, NLi5, CLi6,BLi7and Al14) with low vertical electron affinities (VEA) has been predicted andcharacterized in the present paper. The stability of the studied superatom compoundsis guaranteed by strong M-fluorine interactions, considerable HOMO LUMO gaps, as well as large dissociation energies. Interestingly, the introduction of F significantlyreduces the vertical electron affinities (VEA) of M+. The VEA for the (M-F)+(M=OLi4, NLi5, CLi6, BLi7) cations are within the3.42–3.85eV range, which are lowerthan the IP of Cs atom. The (Al14-F)+cations also exhibit low VEA values of4.60–5.06eV. Hence the studied cationic compounds further enrich the superalkali family.The researches for (OLi4-X)+and (Al14-X)+(X=F, Cl, Br) indicate that fluorination ismore effective than chlorination and bromination to reduce the VEA value of theOLi4+cation, while there is no obvious dependence of the VEA values of larger sized(Al14-X)+on the atomic number of the halogen atoms X. The new knowledge enrichesthe design ideas for superalkalies.3. By means of density functional theory, the optimized structures, relativestabilities and nonlinear optical properties of superalkali-based electridesLi3@calix[4]pyrrole and Li3O@calix[4]pyrrole were investigated. It has been foundthat, replacing alkali metal with superalkalis brings larger NLO responses to theelectrides. In addition, the Li3and Li3O molecules are ionized to a greater degreewhen they are parallel to the plane composed by four N atoms of the calix[4]pyrrolecomplexant. As a result, such structures exhibit larger first hyperpolarizabilities (β0)than the other isomers. The results presented in this work may offer meaningfulreferences to future investigation on other NLO materials with superatoms.4. It has been demonstrated that the Al14cluster can behave as an alkaline earthmetal atom, which arouses our interest to study the reaction of Al14with the H2Omolecules. The mechanism of the reaction between Al14cluster and H2O moleculeshas been investigated by means of density functional theory calculations. Ourcomputational results reveal that reaction begins with a water molecule chemicallyadsorbed to Al14and a nascent Al–O bond forms during the adsorption. A second Alatom neighboring to the Al–O bond acts as Lewis base and accepts the hydrogen atom,which results in the splitting of the O–H bond and the formation of the HAl14(OH)species. In addition, the Al14cluster could absorb more water molecules, and evenrelease H2with addition of multiple water molecules. It has been found that theprocess of superalkaline earth metal Al14adsorbing three water molecules and releasing the first H2is exothermic, during which the Al14moiety basically maintainsthe geometrical integrity of Al14cluster. However, the structure of Al14moietybecomes much more complex and deviates from its original frame after adsorbing anddissociating the fourth H2O molecule. Moreover, the whole process for release of thesecond H2is endothermic. Accordingly, we predict that the superatom may provide apossibility for hydrogen production.更多还原