How reliable is DFT for predicting the redox potentials in polypyridine-based hydrogen evolution catalysts?

metal ions. A set of 10 GGA functionals, each of them with one all-electron and one ECP-corrected basis set, has been systematically applied to the catalyst series. The functional space contains pure, hybrid, dispersion-corrected, and long-range corrected functionals. Our proposed methodologies work impressively well in the case of Fe-containing catalysts, which is particularly encouraging considering the high abundance, low cost, and low toxicity of iron metal. The B3LYP-Def2TZVP, B3LYP-LANL2DZ(f)/6-311++G**, and M06-LANL2DZ(f)/6-311++G** are the three top-performing methods, which have mean average errors (MAEs) of 0.24 V, 0.26 V, and 0.25 V, respectively, when the entire benchmark set of all the catalytic complexes is considered. These methodologies can be preferably used for screening and discovery of novel polypyridine-based catalyst modules for the generation of hydrogen gas, which can be a source of clean and renewable energy.