【作者】 张迪；

【导师】 颜力楷； 苏忠民；

【作者基本信息】 东北师范大学 ， 材料物理与化学， 2011， 硕士

【摘要】 多金属氧酸盐是由前过渡金属离子通过氧连接而成的金属-氧簇类化合物,具有确定的结构,多样化的组成以及优异的物理化学性质,因而多金属氧酸盐在催化、生物活性、医药、分析化学和材料科学等领域显示出诱人的应用前景。随着实验研究的不断深入,多金属氧酸盐及其衍生物的电子性质,氧化还原性质,成键特征,稳定性,以及磁、光、电等性质备受关注。本文通过量子化学计算探讨了多钒酸盐及其多酸类似物的几何结构,轨道特征和氧化还原性质。研究工作主要分为两个部分:1.应用密度泛函理论方法研究了钒氧簇[V^IV₁₈O₄₂（X）]1^3- （X=Cl^-, Br^-, I^-, SH^-, NO₂^-）的几何结构和电子性质,计算结果表明,钒氧笼包封的简单客体离子影响钒氧笼的尺寸,客体离子半径增大,主体笼的尺寸增大。客体离子对该类体系的前线轨道分布以及氧化还原性质的影响很小,说明客体离子和主体笼的相互作用很弱。2.采用密度泛函理论方法研究了多酸型铼氮等电子类似物的结构和电子性质。铼氮等电子类似物的结构和其母体相似,其簇合物的尺寸比相应的母体稍小。电荷布居表明,[XRe₁₂(N₁₂O₂₈]n-可以看成是一个XO₄^n-阴离子包封在一个中性笼内。振动频率分析表明[Re₆N₆O₁₃]^2-和[PRe₁₂(N₁₂O₂₈]^3-是能量最小点,与Re–Ob键的振动模式相比,Re≡N键的振动发生在较高频率区域。[Re₆N₆O₁₃]^2-和[PRe₁₂(N₁₂O₂₈]^3-的HOMO-LUMO能隙以及LUMO能级比相应的母体[W6O19]^2-和[PW₁₂O₄₀]^3-低。可以预测,[Re₆N₆O₁₃]^2-和[PRe₁₂(N₁₂O₂₈]^3-的反应活性强于其母体阴离子。铼氮类似物的轨道特征与其母体相似。与多酸阴离子一样,铼氮类似物也是“电子储库”,可以接受多个电子而其结构没有明显变化。更多还原

【Abstract】 Polyoxometalates （POMs） have been traditionally the subject of study of molecular inorganic chemistry. Yet, these polynuclear molecules, reminiscent of oxide clusters, present a wide range of structures and with them ideal frameworks for the deployment of a plethora of useful magnetic, electronic, catalytic, bioactive and photochemical properties. With the splendid experimental studies, POMs have been recently paid much attention on their electronic structures, redox properties, bonding features, and molecular stabilities.In this thesis, the density functional theory （DFT） has been employed to study the geometrical and electronic structures, bonding character, and redox properties of polyanions. All finished work has been focused on the following aspects:1. The geometrical structures and electronic properties of [VIV18O42（X）]1^3- （X=Cl^-, Br^-, I^-, SH^-, NO₂^-） were investigated by DFT method. The results show that the guest anion affects the size of the host cluster. With the increasing size of guest anion, the size of host cluster increases. The frontier molecular orbital and the LUMO energy of[VIV18O42（X）]1^3- are slightly influenced by the guest anion. It indicates that the interaction between guest anion and the host cluster is weak.2. The investigations of the structural and electronic properties of proposed novel rhenium-nitrido isoelectronic analogues toward several typical polyoxometalates were performed by theoretical approach. The structures of rhenium-nitrido isoelectronic analogues are similar to their parents POMs. The cluster sizes of rhenium-nitrido analogues are slightly smaller than that of related polyoxoanions. The charge populations computed for the [XRe₁₂(N₁₂O₂₈]n- （X= P, Si, Al） clusters support the hypothesis that an oxidized anion is an XO4n- clathrate inside a neutral Re12N12O24 cage. The vibrational frequency analysis show that [Re₆N₆O₁₃]^2- and [PRe₁₂(N₁₂O₂₈]^3- are minima. Comparing with Re–Ob bonds vibrations, Re≡N bonds occur at high frequencies. The HOMO-LUMO gaps and LUMO energies of [Re₆N₆O₁₃]^2- and [PRe₁₂(N₁₂O₂₈]^3- are lower than related parents [W6O19]^2- and [PW12O40]^3- as the d-rhenium orbitals are lower in energy than tungsten orbitals. It suggests that [Re₆N₆O₁₃]^2- and [PRe₁₂(N₁₂O₂₈]^3- could be more reactive than their parent species. The orbital characters in rhenium-nitrido analogues resemble with their related species. The rhenium-nitrido analogue core is a reservoir of electrons that resemble polyoxoanions and can accept many electrons without significantly deforming the framework.更多还原