Metal-mediated catalytic polarisation transfer from parahydrogen to 3,5-dihalogenated pyridines

Ben J Tickner, Marcus Dennington, Benjamin G Collins, Callum A Gater, Theo F N Tanner, Adrian C Whitwood, Peter J Rayner, Daniel P Watts, Simon B Duckett

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The neutral catalysts [IrCl(H) 2(NHC)(substrate) 2] or [IrCl(H) 2(NHC)(substrate)(sulfoxide)] are used to transfer polarization from para hydrogen ( pH 2) to 3,5-dichloropyridine and 3,5-dibromopyridine substrates. This is achieved in a rapid, reversible, and low-cost process that relies on ligand exchange within the active catalyst. Notably, the sulfoxide-containing catalyst systems produced NMR signal enhancements between 1 and 2 orders of magnitude larger than its unmodified counterpart. Consequently, this signal amplification by reversible exchange hyperpolarization method can boost the 1H, 13C, and 15N nuclear magnetic resonance (NMR) signal intensities by factors up to 4350, 1550, and 46,600, respectively (14.0, 1.3, and 15.4% polarization). In this paper, NMR and X-ray crystallography are used to map the evolution of catalytically important species and provide mechanistic rational for catalytic efficiency. Furthermore, applications in spontaneous radiofrequency amplification by stimulated emission and NMR reaction monitoring are also shown.

Original languageEnglish
Pages (from-to)994-1004
Number of pages11
JournalACS Catalysis
Issue number2
Early online date5 Jan 2024
Publication statusPublished - 19 Jan 2024

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© 2024 The Authors. Published by American Chemical Society.

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