Additionally, we present a CEST measurement of the same sample, when the free hydrogen pool has been removed from solution by several minutes of helium bubbling ( Figure ). In this case, the line intensity of the main species is plotted. The resulting CEST spectra clearly shows, that these complexes undergo interexchange (via substrate ligand exchange, compare scheme in figure in the main text), even in the absence of a free hydrogen pool. Hyperpolarized NMR spectra SABRE hyperpolarization experiments were conducted before and after ion exchange of chlorine to PF6 -in methanol and benzene. The SABRE enhancements are comparable, or even better when PF6 -is the counterion of the SABRE active catalyst. Lifetime measurements of the singlet-state.