Hyperpolarizing Small Molecules using Parahydrogen 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 is strongly limited in generality since it requires chemical reactions/ interactions with H 2 . Here we report a new method to widen the scope of PHIP hyperpolarization: a source molecule is produced via PHIP with high 13 C polarization, and precipitated out of solution together with a target species. Spin diffusion within the solid carries the polarization onto 13 C spins of the target, which can then be dissolved for solution-state applications. We name this method PHIP-SSD (PHIP with solid-state spin diffusion) and demonstrate it using PHIP-polarized [1- 13 C]-fumarate as the source molecule, to polarize different 13 C-labelled target molecules. 13 C polarizations of between 0.01 and 3 % were measured on [1- 13 C]-benzoic acid, depending on the molar ratio of fumarate:benzoate in the solid state. We also show that PHIP-SSD does not require specific co-crystallization conditions by grinding dry powders of target molecules together with solid fumarate crystals, and obtain 13 C signal enhancements of between 100 and 200 on [ 13 C, 15 N 2 ]-urea, [1- 13 C]-pyruvate, and [1- 13 C]-benzoic acid. This approach appears to be a promising new strategy for facile hyperpolarization based on PHIP.