Hyperpolarization effects in parahydrogen activation with pnictogen biradicaloids : metal‐free PHIP and SABRE
|Author:||Zhivonitko, Vladimir V.1; Beer, Henrik2; Zakharov, Danila O.1;|
1NMR Research Unit, University of Oulu, P.O. Box 3000, 90014 Oulu (Finland)
2Institute of Chemistry, University of Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock (Germany)
3Leibniz-Institut für Katalyse e.V., Universität Rostock, Albert-Einstein-Strasse 29a, 18059 Rostock (Germany)
|Online Access:||PDF Full Text (PDF, 2 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2021051229792
John Wiley & Sons,
|Publish Date:|| 2021-05-12
Biradicaloids attract attention as a novel class of reagents that can activate small molecules such as H₂, ethylene and CO₂. Herein, we study activation of parahydrogen (nuclear spin‐0 isomer of H₂) by a number of 4‐ and 5‐membered pnictogen biradicaloids based on hetero‐cyclobutanediyl [X(μ‐NTer)₂Z] and hetero‐cyclopentanediyl [X(μ‐NTer)₂ZC(NDmp)] moieties (X,Z=P,As; Ter=2,6‐Mes₂−C₆H₃, Dmp=2,6‐Me₂−C₆H₃). The concerted mechanism of this reaction allowed observing strong nuclear spin hyperpolarization effects in ¹H and ³¹P NMR experiments. Signal enhancements from two to four orders of magnitude were detected at 9.4 T depending on the structure. It is demonstrated that 4‐membered biradicaloids activate H₂ reversibly, leading to SABRE (signal amplification by reversible exchange) hyperpolarization of biradicaloids themselves and their H₂ adducts. In contrast, the 5‐membered counterparts demonstrate rather irreversible parahydrogen activation resulting in hyperpolarized H₂ adducts only. Kinetic measurements provided parameters to support experimental observations.
|Pages:||813 - 817|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
114 Physical sciences
116 Chemical sciences
This work was supported by the Academy of Finland (grant no. 323480), the University of Oulu (Kvantum Institute) and the European Research Council (ERC) under Horizon 2020 (H2020/2018‐2022/ERC Grant Agreement No. 772110). We gratefully acknowledge funding by the DFG (SCHU 1170/12‐2).
|EU Grant Number:||
(772110) UFLNMR - Ultrafast Laplace NMR
|Academy of Finland Grant Number:||
323480 (Academy of Finland Funding decision)
© 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.