Nonresonant SABRE provides an additional versatile hyperpolarization approach in magnetic resonance.

Abstract

Hyperpolarization approaches in magnetic resonance overcome sensitivity limitations imposed by thermal magnetization and are integral to many modern applications. We begin with an overview of hyperpolarization. We then focus on one method, SABRE, which uses parahydrogen to form hydride transition metal complexes, followed by reversible exchange to polarize target molecules in solution. SABRE has produced large signal enhancements (up to 10⁴) on many different molecules, cheaply and rapidly. Here, we demonstrate an unconventional SABRE strategy, applicable to a wide range of targets, that produces field-independent spin order in target molecules which efficiently converts to magnetization. The observed signal is even independent of field direction, and hyperpolarization can be achieved on a lab bench with no field control. We show that this signal arises from creation of two-spin order in targets and discuss ways this strategy should expand SABRE generality and efficiency. We also show that, often, the standard assumption that low-field SABRE requires a singlet-only starting state leads to incorrect results.