Development and Application of Wave Function Based Methods for the Calculation of Nuclear Magnetic Resonance Scalar Couplings and Chemical Shifts

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Nuclear magnetic resonance is one of the most important experimental techniques to investigate the structure of biomolecules. The most important observables in these experiments are chemical shifts and indirect spin-spin couplings. The chemical shifts depend on the electronic environment and allow the quantitative assessment of the structure of the biomolecules. The indirect spin-spin couplings, on the other hand, describe the influence of the binding electrons on the relaxation of the nuclear spins in the magnetic field. Experimentally, the interpretation of these quantities for the investigation of the structure of biomolecules is typically based on empirical knowledge, as the exact calculation of these spectra is not possible. For a better understanding of the experiments, however, such calculations would be highly desirable. The goal of the proposed project is the development of quantum chemical methods for the calculation of nuclear magnetic resonance spectra. The first step is the development of an in silico nuclear magnetic resonance laboratory, which allows the rapid characterization of a large number of molecules by calculating chemical shifts and spin-spin couplings. The nuclear spins and magnetic fields that are needed for these calculations are not described analytically, which would be the traditional approach. Instead, the nuclear spins are calculated via finite elements. This procedure allows the efficient calculation of chemical shifts and spin-spin couplings for a plethora of quantum chemical methods. In the second part of the project, new quantum chemical methods will be developed, which allow the calculation of chemical shifts and spin-spin couplings with high precision. As accuracy and computational cost are typically coupled, the system of interest will be divided into two fragments (core fragment and environment). In the small core fragment, highly accurate quantum chemical methods will be used for the calculation of the observables. In order to keep the computational cost within a reasonable frame, less expensive methods will be used for the description of the environment. This approach will allow the accurate calculation of chemical shifts and spin-spin couplings for biologically relevant molecules.