Synthesis, characterization and electrocatalysis of mono- and di-nickel tetraiminodiphenolate macrocyclic complexes as active site models of [NiFe]-hydrogenases

A series of mononuclear NiII and binuclear NiIINiII macrocyclic complexes were investigated as functional models of the active site of [Ni–Fe]-hydrogenase. The electrocatalytic properties of the compounds were assessed and their efficiency was correlated with the availability of donor atoms in the structure of the macrocycle to accept the proton. The catalysts exhibited a regular activity for proton reduction. Redox levels and plausible electrochemical mechanisms for H2 production are presented as well.

► Electrocatalysis of nickel(II) macrocylic complexes to dihydrogen production.
► Macrocycle ligands containing donor atoms in the structure are more efficient catalysts than those that do not have them.
► For the binuclear complexes, the NiI–NiI state seems to be accessible.