The synthesis and characterization of novel compounds (5-8) as mimetics of [FeFe]-hydrogenase, combining two distinct systems capable of participating in hydrogen evolution reactions (HER): the [(μ-adt)Fe2(CO)6] fragment and M-salen complexes (salen=N,N'-bis(salicylidene)ethylenediamine) (M=Zn, Ni, Fe, Mn), is reported. These complexes were synthesized in high yields via a three-step procedure from N,N'-bis(4-R-salicylidene)ethanediamine) 4 [R=Fe2(CO)6(μ-SCH2)2NCOCH2O]. Structural analysis through spectroscopic, spectrometric, and computational (DFT) methods confirmed distorted tetrahedral and square-planar geometries for Zn-salen and Ni-salen complexes (5 and 6) respectively, while complexes Fe-salen 7 and Mn-salen 8 exhibit square-based pyramidal structures typical of Fe(III) and Mn(III) high-spin salen-complexes. Electrochemical studies revealed different reduction events for [(μ-adt)Fe2(CO)6] and M-salen moieties, but the electrocatalytic experiments in TFA demonstrated a clear cooperative effect between these components, especially at higher acid concentrations. Notably, the Ni-salen (6), Fe-salen (7), and Mn-salen (8) complexes exhibit significant reductions in overpotential, highlighting their potential for enhanced catalytic performance.
Keywords: Hydrogenases; cooperative effects; electrocatalysis; electrochemistry; hydrogen evolution reaction.
© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.