Analysis and prediction of anisotropic nuclear magnetic resonance parameters

该项目的目标是借助计算机模拟以及量子化学能和性质计算来解决溶解在对准介质中的中小型有机和金属有机化合物的核磁共振谱分析和预测问题，以确定半刚性到柔性分子的相对和绝对构型。模型研究和模拟应首先进行测试，并在必要时修改先前使用的分析方法，用于在定义良好的条件下增加复杂性的系统（刚性分子->半刚性（振动）分子->分子具有大振幅运动->分子具有几个构象和大相互转化屏障->分子具有几个构象和小相互转化屏障）。随后，重点将放在实验研究具有高而不是低对称性的小手性分子上，以解决绝对构型问题。用高级从头算方法计算溶质的分子参数（结构、谐波力场、屏蔽张量、自旋-自旋耦合张量、旋向性质）将补充实验数据。溶质和取向介质之间的分子间相互作用势应主要通过量子化学方法来确定，以预测对映体的取向差异，并通过与实验的比较来确定绝对构型。一旦对高度对称的手性体系做到了这一点，目标体系的对称性就会逐渐降低，化合物的灵活性会增加，模型的复杂性会降低，从而得到一种通用的、普遍适用的方法，用于在具有多个构象的体系中分配相对和绝对构型。

The objective of this project is to address with the help of computer simulations as well as quantum chemical energy and property calculations the problem of analysis and prediction for NMR spectra of small to medium sized organic and metalorganic compounds dissolved in alignment media in order to determine relative and absolute configuration of semi-rigid to flexible molecules. Model studies and simulations shall be performed that allow in the first place to test and, if necessary, modify previously employed analysis methodologies for systems under well-defined conditions of increasing complexity (rigid molecules -> semi-rigid (vibrating) molecules -> molecules with large amplitude motions -> molecules with several conformers and large barriers for interconversion -> molecules with several conformers and small barriers for interconversion). Subsequently, the focus will be on experimentally studied small chiral molecules with high rather than low symmetry to address the absolute configuration problem. Molecular parameters (structures, (an)harmonic force fields, shielding tensors, spin-spin coupling tensors, chiroptical properties) of the solute computed with high-level ab initio methods will complement the experimental data. Intermolecular interaction potentials between solute and alignment medium shall be determined primarilly from quantum chemical approaches to predict differences in alignment for the enantiomers and by comparison to experiment assign the absolute configuration. Once this was accomplished for highly symmetric chiral systems, the symmetry of the target system shall gradually be reduced, the flexibility of the compounds increased and the model complexity reduced to arrive at a versatile and generally applicable method for assignment of both relative and absolute configuration in systems with multiple conformers.