University of Oulu

Parahydrogen-induced polarization in H2 activations and hydrogenations mediated by metal-free catalysts

Saved in:
Author: Zakharov, Danila O.1,2
Organizations: 1University of Oulu Graduate School
2University of Oulu, Faculty of Science, Physics, NMR Research Unit (NMR)
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.5 MB)
Persistent link:
Language: English
Published: Oulu : University of Oulu, 2023
Publish Date: 2023-11-13
Thesis type: Doctoral Dissertation
Defence Note: Academic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public discussion in the Auditorium IT115, Linnanmaa, on November 17th, 2023, at 12 o’clock noon
Tutor: Associate Professor Vladimir V. Zhivonitko
Professor Ville-Veikko Telkki
Reviewer: Professor Silvio Aime
Professor Simon Duckett
Opponent: Professor Clifford Russell Bowers
Kustos: Associate Professor Vladimir V. Zhivonitko


The aim of this thesis is to study the metal-free activation of parahydrogen and the subsequent effects of parahydrogen-induced polarization (PHIP). PHIP is a nuclear spin hyperpolarization method that dramatically increases the sensitivity in NMR by enhancing signals in the spectrum. Typically, PHIP experiments involve catalysts based on metal complexes to activate parahydrogen. However, a recent discovery has shown that metal-free H2 activators can also lead to the spin hyperpolarization. At the same time, there were no reports about metal-free catalytic hydrogenations yielding in hyperpolarized products.

The first part of the thesis focuses on metal-free hydrogenations of alkynes mediated by the ansa-aminoborane-based catalyst HCAT. In this research, we performed hydrogenations of various alkynes in a high magnetic field using parahydrogen. During these reactions, HCAT interacted with alkynes to form HCAT-alkyne adducts, which activated the parahydrogen molecules and resulted in the corresponding alkenes. Consequently, we observed enhanced signals of HCAT-alkyne-H2 intermediates, and most importantly, the alkene products. This represents the first example of PHIP effects on the hydrogenation products using a metal-free catalyst. Additionally, by applying PHIP, we studied and confirmed the proposed reaction mechanism.

Next, we proceeded to further investigate metal-free hydrogenations utilizing parahydrogen. In the second paper, we examined hydrogenation of imines facilitated by the catalyst QCAT. These experiments resulted in enhanced signals in amine products. Additionally, we demonstrated the reversibility of a catalytic cycle, wherein the amines could interact with QCAT and parahydrogen, showcasing hyperpolarization of the NH group hydrogens. This study highlights the significance of PHIP experiments in providing valuable mechanistic insights into metal-free hydrogenations.

Finally, we significantly expanded the range of biradicaloid-based metal-free parahydrogen activators. Namely, pnictogen biradicaloids represent another class of metal-free parahydrogen activators, following the ansa-aminoboranes, that exhibit PHIP effects. In our third paper, we employed four- and five-membered biradicaloids containing P or/and As radical centers. Significant findings were achieved with the four-membered As-P biradicaloid, which exhibited a high enhancement factor exceeding three orders of magnitude at 9.4 T, which is a particularly high level for metal-free systems. Furthermore, the reversibility of parahydrogen addition enabled the hyperpolarization of the biradicaloids themselves, thereby demonstrating the example of SABRE-like (Signal Amplification By Reversible Exchange) effect with metal-free catalytic systems.

see all

Osajulkaisut / Original papers

Osajulkaisut eivät sisälly väitöskirjan elektroniseen versioon. / Original papers are not included in the electronic version of the dissertation.

  1. Zakharov, D. O., Chernichenko, K., Sorochkina, K., Yang, S., Telkki, V.-V., Repo, T., & Zhivonitko, V. V. (2022). Parahydrogen‐induced polarization in hydrogenation reactions mediated by a metal‐free catalyst. Chemistry – A European Journal, 28(8), e202103501.

    Rinnakkaistallennettu versio / Self-archived version

  2. Zakharov, D. O., Chernichenko, K., Sorochkina, K., Repo, T., & Zhivonitko, V. V. (2022). Parahydrogen-induced polarization study of imine hydrogenations mediated by a metal-free catalyst. Dalton Transactions, 51(36), 13606–13611.

    Rinnakkaistallennettu versio / Self-archived version

  3. Zhivonitko, V. V., Beer, H., Zakharov, D. O., Bresien, J., & Schulz, A. (2021). Hyperpolarization effects in parahydrogen activation with pnictogen biradicaloids: Metal‐free phip and sabre. ChemPhysChem, 22(9), 813–817.

    Rinnakkaistallennettu versio / Self-archived version

see all

Series: Report series in physical sciences
ISSN: 1239-4327
ISSN-E: 2814-967X
ISSN-L: 1239-4327
ISBN: 978-952-62-3856-2
ISBN Print: 978-952-62-3855-5
Issue: 156
Type of Publication: G5 Doctoral dissertation (articles)
Field of Science: 114 Physical sciences
Copyright information: © University of Oulu, 2023. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.