Detection of pyridine derivatives by SABRE hyperpolarization at zero field

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical tool used in modern science and technology. Its novel incarnation, based on measurements of NMR signals without external magnetic fields, provides direct access to intramolecular interactions based on heteronuclear scalar J-coupling. The uniqueness of these interactions makes each zero-field NMR spectrum distinct and useful in chemical fingerprinting. However, the necessity of heteronuclear coupling often results in weak signals due to the low abundance of certain nuclei (e.g., N-15). Hyperpolarization of such compounds may solve the problem. In this work, we investigate molecules with natural isotopic abundance that are polarized using non-hydrogenative parahydrogen-induced polarization. We demonstrate that spectra of hyperpolarized naturally abundant pyridine derivatives can be observed and uniquely identified whether the same substituent is placed at a different position of the pyridine ring or different constituents are placed at the same position. To do so, we constructed an experimental system using a home-built nitrogen vapor condenser, which allows for consistent long-term measurements, crucial for identifying naturally abundant hyperpolarized molecules at a concentration level of similar to 1 mM. This opens avenues for future chemical detection of naturally abundant compounds using zero-field NMR.

Automated summary

Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique used in modern science and technology for chemical analysis. This study focuses on the use of hyperpolarized naturally abundant pyridine derivatives in zero-field NMR spectroscopy. The researchers developed an experimental system that allowed for consistent long-term measurements, enabling the identification of these hyperpolarized molecules at a concentration level of around 1 mM. This work paves the way for future chemical detection of naturally abundant compounds using zero-field NMR spectroscopy.