Rational ligand choice extends the SABRE substrate scope

Here we report on chelating ligands for Signal Amplification By Reversible Exchange (SABRE) catalysts that permit hyperpolarisation on otherwise sterically hindered substrates. We demonstrate(1)H enhancements of similar to 100-fold over 8.5 T thermal for 2-substituted pyridines, and smaller, yet significant enhancements for provitamin B(6)and caffeine. We also show(15)N-enhancements of similar to 1000-fold and(19)F-enhancements of 30-fold.