Harnessing polarisation transfer to indazole and imidazole through signal amplification by reversible exchange to improve their NMR detectability

Marianna Fekete, Peter J. Rayner, Gary G.R. Green, Simon B. Duckett*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The signal amplification by reversible exchange (SABRE) approach has been used to hyperpolarise the substrates indazole and imidazole in the presence of the co-ligand acetonitrile through the action of the precataysts [IrCl(COD)(IMes)] and [IrCl(COD)(SIMes)]. 2H-labelled forms of these catalysts were also examined. Our comparison of the two precatalysts [IrCl(COD)(IMes)] and [IrCl(COD)(SIMes)], coupled with 2H labelling of the N-heterocyclic carbene and associated relaxation and polarisation field variation studies, demonstrates the critical and collective role these parameters play in controlling the efficiency of signal amplification by reversible exchange. Ultimately, with imidazole, a 700-fold1H signal gain per proton is produced at 400 MHz, whilst for indazole, a 90-fold increase per proton is achieved. The co-ligand acetonitrile proved to optimally exhibit a 190-fold signal gain per proton in these measurements, with the associated studies revealing the importance the substrate plays in controlling this value.

Original languageEnglish
Article numberMRC4607
Pages (from-to)1-31
Number of pages31
Early online date11 May 2017
Publication statusE-pub ahead of print - 11 May 2017

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© 2017, The Author(s).This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.


  • Imidazole
  • Indazole
  • Iridium catalyst

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