Temperature-Sensitive\nMagnetic Resonance Probes: Leveraging\nHyperpolarized Pyridine-2-Carbaldehyde and SABRE for Real-Time Temperature\nSensing

In this study, we developed a novel\napproach for real-time,\ntemperature-sensitive\nnuclear magnetic resonance (NMR) measurements using signal amplification\nby reversible exchange (SABRE). We discovered that pyridine-2-carbaldehyde\n(A) exhibits different behavior depending on temperature, showing\nhigh hyperpolarization efficiency. In contrast, its reversible reaction\nproduct, the hemiacetal form (A′), is not affected by temperature.\nExploiting this difference, we achieved a reliable polarization enhancement\nratio without internal standard materials, even at low concentrations.\nOur method overcomes challenges associated with SABRE for 2-functionalized\npyridines, enabling direct temperature monitoring in real-time NMR\nstudies. We successfully applied it to monitor temperatures in solutions\ncontaining SABRE-inactive compounds like caffeine. Furthermore, we\ndemonstrated its efficacy using a 60 MHz benchtop NMR spectrometer,\nvalidating its potential in challenging environments where conventional\ntechniques may be limited. This technique shows promise for influencing\nthe magnetic resonance field, potentially facilitating more accurate\nreal-time analyses of molecular reactions and structures. Future research\nwill focus on adapting this method for biological settings, aiming\nto stimulate advancements in NMR and magnetic resonance imaging (MRI)\napplications.