Temperature-Sensitive Magnetic Resonance Probes: Leveraging Hyperpolarized Pyridine-2-Carbaldehyde and SABRE for Real-Time Temperature Sensing

In this study, we developed a novel approach for real-time, temperature-sensitive nuclear magnetic resonance (NMR) measurements using signal amplification by reversible exchange (SABRE). We discovered that pyridine-2-carbaldehyde (A) exhibits different behavior depending on temperature, showing high hyperpolarization efficiency. In contrast, its reversible reaction product, the hemiacetal form (A′), is not affected by temperature. Exploiting this difference, we achieved a reliable polarization enhancement ratio without internal standard materials, even at low concentrations. Our method overcomes challenges associated with SABRE for 2-functionalized pyridines, enabling direct temperature monitoring in real-time NMR studies. We successfully applied it to monitor temperatures in solutions containing SABRE-inactive compounds like caffeine. Furthermore, we demonstrated its efficacy using a 60 MHz benchtop NMR spectrometer, validating its potential in challenging environments where conventional techniques may be limited. This technique shows promise for influencing the magnetic resonance field, potentially facilitating more accurate real-time analyses of molecular reactions and structures. Future research will focus on adapting this method for biological settings, aiming to stimulate advancements in NMR and magnetic resonance imaging (MRI) applications.