Analysis and prediction of anisotropic nuclear magnetic resonance parameters

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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.