New methods for the measurement and evaluation of anisotropic NMR parameters for the configurational assignment of molecular structures

• Applicants: Professor Dr. Christian Griesinger; Professor Dr. Michael Reggelin
• Subject Area: Analytical Chemistry ; Organic Molecular Chemistry - Synthesis and Characterisation ; Polymer Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 528400063

The application of anisotropic NMR parameters in the structure determination of dissolved organic compounds is of increasing importance. This is especially true for residual dipolar couplings (RDCs), but also for residual quadrupolar couplings (RQCs). Recently, residual chemical shift anisotropy (RCSA) has been added, mainly by the Griesinger group. In addition to 13C-RCSA, methods have been developed that also allow 1H-RCSA to be measured, which is particularly attractive for reasons of measurement sensitivity. The measurement of anisotropic parameters requires a restriction of the isotropic movement of the molecules, which up to now has essentially been achieved by lyotropic liquid crystalline phases (LLC) or by mechanically deformed polymer gels. Electric fields are now to serve as a completely new variant for the generation of this "weak alignment", which bring this about either indirectly through alignment of the polymer chains, or directly through interaction of the E-field with the analytes. In connection with this measurement method project, which is being worked on by both groups (CG and MR) new approaches to structurally diverse, helically chiral, polyacetylenes and polyisonitriles are to be developed. These will then serve both as a basis for fundamental investigations into the problem of enantiomer-differentiating alignment and for solving challenging problems of relative configurations of natural products. In collaboration, attempts will be made to determine absolute configurations. For this purpose, NMR data will be collected in the chiral media and then processed using novel software solutions.

• DFG Programme: Research Grants