Copper Ligation and Nuclearity Dictate the Solution Dynamics and Hydrogen Evolution Activity of Discrete Mo–Cu Sulfide Clusters

. DFT calculations attribute this difference to attenuated sulfur basicity resulting from increased sulfur saturation, ancillary ligand donation, or overall charge, while experimental (single-crystal XRD, DOSY) studies also indicate cluster speciation under catalytic conditions. Collectively, this work clarifies the electronic and structural criteria for optimizing sulfur-centered HER using discrete ternary chalcogenide catalysts.