𝛿𝑃 thus can be used to characterize the efficiency of the -𝑆 𝑇 0 conversion process, which is due to symmetry breaking in H 2 bound to the SABRE complex. Symmetry breaking can be due to the chemical shift difference between the two protons and/or to subtler effects of J-couplings. In the SABRE complex, the 1 H-15 N J-couplings are sizeable; furthermore, there is a large difference in the couplings and , so that it 𝐽 𝐴𝑀 = 𝐽 𝐴 ′ 𝑀 ′ 𝐽 𝐴 ′ 𝑀 = 𝐽 𝐴𝑀 ′ has been estimated that Hz. As a 𝛿𝐽 = 𝐽 𝐴𝑀 -𝐽 𝐴 ′ 𝑀 ≈ 20 consequence, the two pH 2 -nascent protons become magnetically non-equivalent and the effective value 𝛿𝜔 becomes non-zero. We have studied the effect of symmetry breaking through magnetic non-equivalence by varying the enrichment of N nuclei, i.e., by using a mixture of 14 N-Py and N-Py (the fast relaxing quadrupolar 14 N nuclei do not alter the spin dynamics of the proton system). Please do not adjust margins Please do not adjust margins Py); straight lines are drawn to guide the eye. We used solutions after ion exchange with AgPF 6 .