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

Kristina Sorochkina, Vladimir V. Zhivonitko, Konstantin Chernichenko, Ville Veikko Telkki, Timo Repo, Igor V. Koptyug

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)903-907
Number of pages5
JournalJournal of Physical Chemistry Letters
Volume9
Issue number4
DOIs
Publication statusPublished - 15 Feb 2018

Keywords

  • FRUSTRATED LEWIS PAIRS
  • PARA-HYDROGEN
  • INDUCED POLARIZATION
  • NMR
  • MRI
  • RELAXATION
  • ALIGNMENT
  • SABRE
  • ORDER
  • P-31

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