Supramolecular approaches for light-induced spin hyperpolarisation

• Applicant: Professorin Dr. Sabine Richert
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545606231

Magnetic resonance techniques, such as nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and their imaging variants (e.g. MRI), have found widespread use in research, industry, as well as diagnostic medicine. However, they all suffer from one major drawback, which is their low sensitivity. A promising way to overcome this sensitivity limitation is spin hyperpolarisation. In NMR hyperpolarization experiments, such as DNP, hyperpolarization is often achieved by transferring electron spin polarization to nuclei. Classical DNP experiments are limited by Boltzmann population differences, but it is evident that much larger signal enhancements can in principle be achieved when making use of light-induced electron spin polarization. With the proposed work, we will contribute to the field of spin hyperpolarization by developing new experimental protocols for an efficient transfer of light-induced electron spin polarization to nuclei. To unravel important mechanistic details, we will work with highly modular model systems consisting of an organic chromophore and a stable radical and study their optical and magnetic properties with the help of several complementary spectroscopic techniques. The triplet state of the chromophore, generated upon photoexcitation, serves as the source of electron spin polarization. Chromophore triplet formation and associated side processes will be monitored by transient UV-vis spectroscopy, while transient EPR and transient NMR techniques will be used to detect and quantify the generation of electron spin polarization and its transfer to nuclear spins. Establishing structure-function relationships requires well-defined structures and the ability to make systematic design modifications. This is achieved here by exploiting the benefits of supramolecular chemistry. The modularity of the approach will further allow us to screen a large number of chromophore-radical combinations and conditions, with the goal to optimize the generation and transfer of electron spin polarization. This work will pave the way for the rational design of novel polarization transfer agents for spin hyperpolarization and the development of new experimental protocols for signal enhancement in both EPR and NMR experiments.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partner: Dr. Andreas Rodrigo Vargas Jentzsch