Reversible hyperpolarization of ketoisocaproate using sulfoxide‐containing polarization transfer catalysts
Tickner, Ben. J.; Ahwal, Fadi; Whitwood, Adrian C.; Duckett, Simon B. (2021-01-07)
B. J. Tickner, F. Ahwal, A. C. Whitwood, S. B. Duckett, ChemPhysChem 2021, 22, 13. https://doi.org/10.1002/cphc.202000825
© 2020 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.
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe202102013401
Tiivistelmä
Abstract
The substrate scope of sulfoxide‐containing magnetisation transfer catalysts is extended to hyperpolarize α‐ketoisocaproate and α‐ketoisocaproate‐1‐[¹³C]. This is achieved by forming [Ir(H)₂(κ²‐ketoisocaproate)(N‐heterocyclic carbene)(sulfoxide)] which transfers latent magnetism from p‐H₂ via the signal amplification by reversible exchange (SABRE) process. The effect of polarization transfer field on the formation of enhanced ¹³C magnetization is evaluated. Consequently, performing SABRE in a 0.5 μT field enabled most efficient magnetisation transfer. ¹³C NMR signals for α‐ketoisocaproate‐1‐[¹³C] in methanol‐d⁴ are up to 985‐fold more intense than their traditional Boltzmann derived signal intensity (0.8 % ¹³C polarisation). Single crystal X‐ray diffraction reveals the formation of the novel catalyst decomposition products [Ir(μ‐H)(H)₂(IMes)(SO(Ph)(Me)₂)]₂ and [(Ir(H)₂(IMes)(SO(Me)₂))₂(μ‐S)] when the sulfoxides methylphenylsulfoxide and dimethylsulfoxide are used respectively.
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