Structural chemistry of subvalent oxo- and nitrdiometalates: chemical twinning of ionic and metallic building units

亚价化合物在固态化学中占有特殊的地位。离子和金属键的贡献在它们内部以一种独特的方式实现。结构单元可以看作是从(金属间)相切割出来的，与离子结构的基元周期性地交替，形成有序的晶格。因此，二价化合物是以金属键为主的区域与离子键占优势的区域共存的固体。根据结构单元的两个不同特征，亚价化合物结合了金属和离子固体的典型行为。亚价化合物总体上表现出良好的金属行为，但传导电子与离子区域的局部库仑势的相互作用导致了有趣的新效应。金属和离子特性的意外组合有望导致新材料的出现。金属导电性和例如局域磁性过渡金属中心的组合可能导致电子或数据存储设备的感兴趣的材料。改变离子和金属结构区域的体积分数可以合理地设计低维金属导体，甚至是由不相互作用的原子基团组成的小量子点。此外，强各向异性光学材料也是可以想象的。关于亚价化合物的固态化学的这些方面的系统工作很少。这类物质最早的代表是重碱土金属的碱金属亚氧化物和亚氮化物。我们成功地通过合成了碱金属亚硝酸盐和第一个含有复杂的四面体氧代和硝基金属酸根阴离子的碱土亚硝酸盐，并通过表征新的结构家族，成功地拓宽了亚价化合物的家族。这个项目的目的是系统地扩大亚硝基和亚硝基金属酸盐的类别，并表征新代表的性质。通过比较尽可能多的亚价金属酸盐的个体实例，可以更深入地了解离子和金属结构亚基的相互作用及其对宏观性质的影响。根据电导率、热容、磁悬浮性的测量，结合电子结构的量子化学计算，将建立一幅全面的二价化合物结构-性质关系的图景。

Subvalent compounds hold a special position within solid state chemistry. Ionic and metallic bonding contributions are realised within them in a unique manner. Structural units which can be regarded as cut-outs from (inter-)metallic phases alternate periodically with motifs from ionic structures and form an ordered crystal lattice. Subvalent compounds thus are solids in which areas with perdominantly metallic bonding coexist with areas in which ionic bonding prevails. According to the two different characters of the structural building units, subvalent compounds combine the typical behaviour of metals and ionic solids. Subvalent compounds show overall good metallic behavour but interaction of the conduction electrons with the local Coulomb potentials from the ionic regions lead to interesting new effects. Unexpected combinations of metallic and ionic properties can prospectively lead to novel materials. The combination of metallic conductivity and e. g. ocalised magnetic transition metal centres could result in matierals of interest for electronic or data storage devices. Modifying the volume fraction of ionic and metallic structural areas could enable the rational design of low-dimensional metallic conductors or even quantum dots of small, not interacting atomic groups of atoms. Also strongly anisotropic optical materials are conceivable.Systematic work on these aspects of the solid state chemistry of subvalent compounds is scarce. The first representatives of this class of substances were the alkali metal suboxides and he subnitrides of the heavy alkaline earth metals. We succeeded in broadening the family of subvalent compounds by synthesising alkali metal suboxometalates and the first alkaline earth subnitridometalates containing complex, tetrahedral oxo- and nitridometalate anions and by characterising new structural families.This project aims at a systematic expansion of the classes of suboxo- and subnitridometalates and the characterisation of the properties of new representatives. By comparing as many individual examples of subvalent metalates as possible a ddeper insight for the interaction of ionic ande metallic structural subunits and its influence on macroscopic properties may be gained. A comprehensive picture of the structure-property relations of subvalent compounds based on measurements of electric conductivity, heat capacity, magnetic suscebility in combination with quantum chemical calculations of the electronic structure is to be established.