Novel NHC-iridium complexes for advanced application of hyperpolarized NMR

Hyperpolarization with parahydrogen emerged as an important method for increasing the signal strength of magnetic resonance measurements like NMR or MRI. In SABRE (signal amplification by reversible exchange) spin order is transferred via a reversibly formed NHC-iridium complex. Recent strategies to apply SABRE in living cells or in vivo in medicine use the separation of the complexes by filtration or heterogeneous catalysts. The development of new heterogeneous systems, biphasic systems and the synthesis of catalysts with improved water solubility are important for the advanced applications of SABRE. In this work, a new class of NHC-iridium-functionalized linker molecules was used to develop metal-organic frameworks for the heterogeneous catalysis in SABRE NMR. The new NHC-iridium complexes were successfully established in SABRE experiments. Additionally, NHC-iridium complexes were modified to be used in a biphasic system of water and fluorinated solvents for an easy separation of the catalyst and the enhanced substrate. Furthermore, novel PEG-functionalized catalysts were designed with improved solubility in water. Efforts made in this work should help to bring forward a promising technology to gain new possibilities in natural science and medicine.