Hyperpolarizing Small Molecules using Parahydrogen-Induced Polarization and Solid-State Spin Diffusion

Parahydrogen-induced polarization (PHIP) is an inexpensive way to produce hyperpolarized molecules with polarization levels of >10% in the solution-state, but PHIP is strongly limited in generality since it requires chemical reactions or interactions with H2. Here we report a new method to widen the scope of hyperpolarization via PHIP: a source molecule is produced via PHIP with high 13C polarization, and precipitated out of solution together with a target species. Spin diffusion in the solid state carries the polarization onto 13C spins in the target species, and the solid can subsequently be redissolved for NMR applications. We name this method PHIP-SSD (PHIP with solid-state spin diffusion) and demonstrate it using PHIP-polarized [1-13C]fumarate as the source molecule, to polarize the target molecules [13C4]fumarate, [1-13C]acetylene dicarboxylate, and [1-13C]benzoic acid. 13C signal enhancements of between 1000 and 3000 were measured on the target molecules at 1.9 T. This approach appears to be promising for polarizing a wider range of molecules via PHIP.