Copper Ligation and Nuclearity Dictate the Solution Dynamics and Hydrogen Evolution Activity of Discrete Mo-Cu
Lauren T Feden1, Eryck García L1, Gwendolyn A Bailey1
1Department of Chemistry, University of Minnesota, Twin Cities, Minneapolis, Minnesota 55455, United States.
None:
Ternary chalcogenides comprising Mo/W thiometallates and first-row metals are of significant interest for applications in laser technology, telecommunications, sensing, and catalysis. Discrete cluster variants have emerged as powerful nanoscale alternatives, offering a modular platform to interrogate and tune physicochemical properties with atomic precision. Recently, we reported [Tp*MoS3(CuSPh)2]- ([1•(CuSPh)2]-; Tp* = tris(3,5-dimethylpyrazolyl)borate), a discrete analog of layered Cu2MoS4 and functional hydrogen evolution reaction (HER) electrocatalyst. Computational analysis revealed that [1•(CuSPh)2]- operates via a sulfur-centered HER pathway; however, the fundamental structure-function relationships linking copper ligation and nuclearity to catalytic performance remained undefined. Herein, we report the synthesis and electrocatalytic evaluation of cluster series [1•(CuX)n]- and [1•(CuL)nn-1 (X = StBu, OAc, halide; L = NCMe, py; n = 2,3) bearing varied copper ligands and nuclearity. Electrocatalytic studies show that the clusters are markedly less active for HER than [1•(CuSPh)2]-. 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.
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