Hydrogen Evolution by FeIIIMolecular Electrocatalysts Interconverting between Mono and Di-Nuclear Structures in Aqueous Phase

Anew FeL/Fe2L2 manifold,with HL= 2-({[di(2-pyridyl)methyl]-(methyl)amino}methyl)phenol, was preparedingram scale (> 50%yield) and characterized in solution and solid state. The monomer/dimer interconversion is controlled in aqueous phase, upon varying thepHconditions. The electrocatalytic hy-drogen evolution reaction (HER) occurs through the FeL mono-mer with added trifluoroacetic acid (TFA)and through the Fe2L2 m-oxo dimer in acetate buffer (pH 4.9), with an overpo-tential of about 1Vand faradaic yield up to 75 %. The resulting icat/ip valuesinthe range 15–28are among the highest report-ed for Fe-based electrocatalysts (icat is the catalytic current, whereas ip is the current of an Fe-based redox event).