Liquid-Phase Parahydrogen-Induced Polarization (PHIP) with Ligand-Capped Platinum Nanoparticles

The low sensitivity of NMR, which is dictated by the weakness of the interaction between nuclear spins and the applied magnetic field, is probably its greatest limitation for more general applications, especially in biological systems. PHIP exploits the high spin order of the parahydrogen molecule to induce nuclear spin alignment and consequently the hyperpolarization resulting in the strong NMR signal enhancements even at low magnetic fields. In this study, the liquid-phase hydrogenation catalyzed by mercaptosuccinic acid-capped Pt-0 nanoparticles was carried out with ALTADENA. The reaction of parahydrogen with several alkynes and alkenes gave PHIP enhancement factors of up to 150 (P = 0.72%) at 600 MHz and room temperature, without preactivation of the hydrogenation catalyst. The hyperpolarization was observed for partially as well as fully hydrogenated products, also involving protons other than the ones introduced in the hydrogenation. The proposed transfer of polarization to these protons during adiabatic transfer of the sample from low to high field was confirmed by a simulation study.