Strong ³¹P nuclear spin hyperpolarization produced via reversible chemical interaction with parahydrogen

Abstract

Substantial (31)P NMR signal enhancement of more than two orders of magnitude at 7 T for free and bound PPh3 species was observed under reversible interaction of (PPh3)3Ir(H2)Cl with parahydrogen. The large improvement in sensitivity made single-shot (31)P NMR imaging of a model object possible. The observed effects are temperature and magnetic field dependent as shown experimentally and theoretically.

NMR Signal Amplification by Reversible Exchange of Sulfur‐Heterocyclic Compounds Found In Petroleum

“…[14] Additional experimental details are provided in the Supporting Information (SI). When B T is roughly matched to the spin-spin coupling ( J H-H ) between nascent parahydrogen-derived hydride protons on the metal center, [4b, 15] a coherent polarization transfer from hydride protons to the protons of the substrate molecule occurs (Figure 2c)--in accord with conventional SABRE of N-heterocycles. [3, 16] Once polarization transfer occurs on the Ir-hexacoordinate complex, the HP substrate molecules and hydride hydrogens exchange with free substrate and parahydrogen in solution, allowing the SABRE hyperpolarization cycle to continue as it reaches the maximum hyperpolarization level at steady state (which typically occurs in seconds).…”

“…To date, SABRE hyperpolarization of N-heterocycles has been demonstrated successfully by many research groups. [4] Despite being structurally limited to hyperpolarization of N-heterocycles, the SABRE technique has been applied for structural studies [5] of coffee extracts [6] and biofluids, [7] in addition to hyperpolarization of contrast agents for biomedical applications. [4b, 8] …”

“…The activated form of the catalyst previously shown to be the most potent for SABRE of N-heterocycles (Ir-IMes hexacoordinate complex [4a] ) was employed for chemical exchange with parahydrogen and the to-be-hyperpolarized sulfur-containing substrates (S), Figure 1a. A previously developed high-pressure setup [14] was employed with a magnetic field for polarization transfer ( B T ) provided by a small solenoid (Figure 1b).…”

NMR Hyperpolarization Techniques of Gases

“…[11c] This seminal discovery of Bowers and Weitekamp opened up a new strategy for hyperpolarization of various compounds, and currently PHIP and its recent modification, SABRE (Signal Amplification By Reversible Exchange), [8] are used to obtain HP molecules with 1 H, [11c, 200b] 13 C, [12] 15 N, [13d] 19 F, [14] and 31 P [15] nuclei in a hyperpolarized state. Detailed explanation of the spin dynamics and chemical kinetics behind PHIP can be found in several comprehensive reviews.…”

“…[8] . A wide range of nuclei can be directly hyperpolarized, including 1 H, [9] 3 He, [10] 7 Li [11] , 13 C, [1c, 12] 15 N, [13] 19 F, [14] 31 P, [15] 83 Kr, [16] and 129 Xe, [4,17] among others. [18] Hyperpolarized (HP) substances are revolutionizing the fields of NMR spectroscopy and magnetic resonance imaging (MRI), because many applications that were previously impractical because of weak NMR signals (e.g.…”