466. In Situ Hyperpolarization Enables ¹⁵N and ¹³C Benchtop NMR at Natural Isotopic Abundance

Raphael Kircher, Jingyan Xu, and Danila A. Barskiy, JACS (2023), DOI: 10.1021/jacs.3c10030

Without employing isotopic labeling, we demonstrate the generation of 15N and 13C NMR signals for molecules containing −NH2 motifs using benchtop NMR spectrometers (1−1.4 T). Specifically, high-SNR (>50) detection of ammonia, 4-aminopyridine, benzylamine, and phenethylamine dissolved in methanol or dichloromethane is demonstrated after only 10 s of parahydrogen bubbling using signal amplification by reversible exchange and applying a pulse sequence based on spin-lockinduced crossing. Optimization of the sequence parameters allows us to achieve up to 12% 15N and 0.4% 13C polarization in situ without the need for the sample transfer typically employed in other hyperpolarization methods. Moreover, hyperpolarization is generated continuously without having to stop the parahydrogen bubbling to reset magnetization, paving the way toward fast 2D spectroscopic methods and relaxometry. The provided methodology may find application for the identification of diluted chemicals