Toward Continuous Production of Catalyst-Free Hyperpolarized Fluids Based on Biphasic and Heterogeneous Hydrogenations with Parahydrogen

Abstract

It is demonstrated that hyperpolarized catalyst-free gases can be produced in a gas–liquid biphasic hydrogenation with parahydrogen using a dissolved catalyst and gaseous reactants. The reaction product is shown to return to the gas phase while retaining a substantial level of nuclear spin hyperpolarization, providing a complete separation of the hyperpolarized substance from the catalyst. The approaches based on biphasic and heterogeneous hydrogenations are shown to be suitable for producing hyperpolarization in a continuous mode. Subsequent gas dissolution can be added to yield solutions of hyperpolarized substances. Extension to a broader range of hyperpolarized substances is shown to be possible based on the hydrogenation of liquid vapors.

Toward Biocompatible Nuclear Hyperpolarization Using Signal Amplification by Reversible Exchange: Quantitative in Situ Spectroscopy and High-Field Imaging

“…14,24 The quality control and equipment necessary for in vivo experimentation has been described, but the technique is not yet available as a “push-button” method. 25−28 Recently, the detection and quantification of 13 C-polarization achieved via such a transfer at a B 0 field of ≈50 mT 29 and steps toward a catalyst-free pH 2 -hyperpoalrization 30 was presented and this can be considered as an important step in moving toward routine and reliable biomedical application.…”

High‐Resolution 3D Proton MRI of Hyperpolarized Gas Enabled by Parahydrogen and Rh/TiO2 Heterogeneous Catalyst

“…However, homogeneous PHIP hydrogenation poses the problem of catalyst separation, which is the main obstacle for its potential biomedical use. [13] Metal (e.g., Rh I ) complexes dissolved in organic solvents can be also used for producing catalyst-free HP fluids by bubbling parahydrogen and substrate gas mixtures through the solution of the homogeneous catalyst, [14] but the volatility of the solvent may be a problem for potential biomedical use. Furthermore, these complexes are prone to oxidation, [15] which can degrade their catalytic activity and HP contrast agent production.…”

NMR Hyperpolarization Techniques of Gases

“…In the demonstration of this approach it was shown that the reaction product can return to the gas phase while retaining a significant degree of hyperpolarization. [213] This feature significantly extends the range of gases that can be hyperpolarized. It was shown that utilization of a simple experimental procedure allows one to achieve signal enhancements of 300 for propyne hydrogenation to propylene using the bidentate cationic complex [Rh(PPh 2 -(CH 2 ) 4 -PPh 2 )(COD)]BF 4 .…”

“…It was shown that utilization of a simple experimental procedure allows one to achieve signal enhancements of 300 for propyne hydrogenation to propylene using the bidentate cationic complex [Rh(PPh 2 -(CH 2 ) 4 -PPh 2 )(COD)]BF 4 . [213] Another approach for HP gas production is the use of homogeneous catalysts based on a judicious choice of the metal complex (homogeneous hydrogenation catalyst) in which the desired unsaturated substrate is coordinated to the metal center. [214] In that case hydrogenation with parahydrogen allows the substrate to leave the metal center and to migrate to a different phase with preservation of the spin order of the two nascent protons derived from the para -H 2 molecule.…”