Flipped Spin-State Resists Cobalt Poisoning for the Durable Electrocatalytic Deuteration of N-Heterocyclic Compounds.

Electrocatalytic deuteration represents a sustainable method for synthesizing deuterated N-heterocycles, which are scaffolds for drug development. However, the utility of this transformation is severely restrained by strong orbital interactions between metal sites and the lone pairs of N atoms that lead to irreversible catalyst deactivation. Here, we propose a Mn3Co7 alloy electrocatalyst that triggers a high-spin-to-low-spin transition in Co. The flipped spin state originates from tuned d-electron pairing, promoting electron occupation in antibonding orbitals and weakening the Co-N bond. The reduced adsorption energy that facilitates the desorption of N-heterocycles is revealed to be the key factor driving the improved catalytic durability. This strategy enables a scaled-up electrosynthesis with a yield of 92.5% at 1.25 A to obtain 10 g of deuterated piperazine hydrochloride. The methodological universality of diverse unsaturated N-heterocycles highlights the application potential.