Determination of oxidation states based on single-crystal diffraction experiments

元素的氧化态是理解其化学性质的核心概念。然而，它不能直接访问。即使是通过复杂的实验装置进行的间接评估也往往是有限的，或者只能应用于某些元素。在这个项目中，一个新的程序，采用色散校正将在常规软件中实施的单晶X射线衍射实验的分析，使常规实验室设备的使用，用于确定氧化态。这个新软件将依靠多波长实验来获得给定元素相对于相应中性原子的色散光谱的位移，以推导其氧化态。所需的计算和改进是使用Olex2中的非球形原子（“NoSpherA2”）进行的。这是我在以前的一个项目中部分开发的软件，它允许使用基于手头晶体结构电子密度的量子化学计算的定制原子形状因子。计划进一步实施“身份解析”和“有效核心潜力”。这两种技术在量子化学中都很成熟，可以加速波函数的计算。因此，在非球形形状因子推导期间所需的计算时间将被带到常规应用的规模和实用性。采用合作者当前研究项目中的晶体样品，将评估新方法的实际准确性和可靠性。本研究的主要物质类别将是催化和光氧化还原活性分子。后者也将在其激发状态下进行检查，使用实验装置，该装置允许在衍射实验期间进行额外的照射。这将提供激发态和基态晶体结构之间的色散和电子结构的差异。

The oxidation state of an element is a central concept for understanding its chemical properties. However, it is not directly accessible. Even indirect evaluation through complex experimental setups are often limited or can only be applied to certain elements. In this project, a new procedure employing dispersion correction will be implemented in routine software for analyses of single crystal X-ray diffraction experiments, to enable the use of routine lab-equipment for the determination of oxidation states. This new software will rely on multi-wavelength experiments to obtain the shift of dispersion spectra of a given element with respect to the corresponding neutral atom to derive its oxidation state. The required calculations and refinements are carried out using Non-Spherical-Atoms in Olex2 (“NoSpherA2”). This is a software developed in parts by me in a previous project, which allows the use of tailor-made atomic form factors based on quantum chemical calculations of the electron density of the crystal structure at hand. An additional implementation of the “Resolution of Identity” and the “Effective Core potentials” is planned. Both techniques are well established in quantum chemistry to speed up wavefunction calculations. Thereby the computational time required during non-spherical form factor derivation will be brought to a scale and practicability for routine application. Employing crystal samples from current research projects of collaborators, the practical accuracy and reliability of the new methods will be evaluated. The main class of substances for this investigation will be catalytically and photo-redox active molecules. The latter are to be also examined in their excited state, using an experimental setup, which allows additional irradiation during the diffraction experiment. This will give access to the differences in dispersion and electronic structure between the excited and ground state crystal structure.