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Spontaneous 15N Nuclear Spin Hyperpolarization in Metal-Free Activation of Parahydrogen by Molecular Tweezers.


ABSTRACT: The ability of frustrated Lewis pairs (FLPs) to activate H2 is of significant interest for metal-free catalysis. The activation of H2 is also the key element of parahydrogen-induced polarization (PHIP), one of the nuclear spin hyperpolarization techniques. It is demonstrated that o-phenylene-based ansa-aminoboranes (AABs) can produce 1H nuclear spin hyperpolarization through a reversible interaction with parahydrogen at ambient temperatures. Heteronuclei are useful in NMR and MRI as well because they have a broad chemical shift range and long relaxation times and may act as background-free labels. We report spontaneous formation of 15N hyperpolarization of the N-H site for a family of AABs. The process is efficient at the high magnetic field of an NMR magnet (7 T), and it provides up to 350-fold 15N signal enhancements. Different hyperpolarization effects are observed with various AAB structures and in a broad temperature range. Spontaneous hyperpolarization, albeit an order of magnitude weaker than that for 15N, was also observed for 11B nuclei.

SUBMITTER: Sorochkina K 

PROVIDER: S-EPMC5862329 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Spontaneous <sup>15</sup>N Nuclear Spin Hyperpolarization in Metal-Free Activation of Parahydrogen by Molecular Tweezers.

Sorochkina Kristina K   Zhivonitko Vladimir V VV   Chernichenko Konstantin K   Telkki Ville-Veikko VV   Repo Timo T   Koptyug Igor V IV  

The journal of physical chemistry letters 20180208 4


The ability of frustrated Lewis pairs (FLPs) to activate H<sub>2</sub> is of significant interest for metal-free catalysis. The activation of H<sub>2</sub> is also the key element of parahydrogen-induced polarization (PHIP), one of the nuclear spin hyperpolarization techniques. It is demonstrated that o-phenylene-based ansa-aminoboranes (AABs) can produce <sup>1</sup>H nuclear spin hyperpolarization through a reversible interaction with parahydrogen at ambient temperatures. Heteronuclei are usef  ...[more]

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