Utilisation of water soluble iridium catalysts for signal amplification by reversible exchange

The catalytic hyperpolarisation of pyridine, 3-hydroxypyridine and oxazole by the Signal Amplification By Reversible Exchange (SABRE) process is achieved by a series of water soluble iridium phosphine and N-heterocyclic carbene dihydride complexes. While the efficiency of the SABRE process in methanol-d(4) solution or ethanol-d(6) solution is high, with over 400-fold H-1 polarisation of pyridine being produced by [Ir(H)(2)(NCMe)(py)(IMes)(monosulfonated-triphenylphosphine)] BF4, changing to a D2O or a D2O-ethanol solvent mixture leads to dramatically reduced activity which is rationalised in terms of low H-2 solubility.