Electronic Properties of a Structural Model of Single-Atom Co-Adsorption to MoS₂ Edge Sites

Molecular-level insight into how single-atom transition metal dopants modulate electronic structure at the edge sites of MoS₂ remains an underdeveloped area of research that is essential for the design of efficient catalysts. The present work describes the synthesis of a cobalt-substituted thiomolybdate dimer, [(CpMo)₂(Cp*Co)(μ₃-S)₂(μ₂-S₂CH₂)], which serves as a molecular model for cobalt adsorption at the MoS₂ edge. Spectroscopic and magnetic measurements establish a diamagnetic, closed-shell ground state for the heterobimetallic complex. Time-dependent density functional theory (TD-DFT) calculations indicate significant electronic communication across the "CoMo₂S₄" assembly. Electrochemical studies reveal three reversible redox processes, assigned to a Co-centered reduction and Mo-based oxidations. Access to the reduced and oxidized species was possible, allowing for investigation into redox-dependent changes to electronic structure. Reduction centered at the cobalt atom generates a Co(II)Mo(III)₂ complex, whereas one-electron oxidation affords a mixed-valent Co(III)Mo(IV)Mo(III) species that features electron delocalization across the "Mo₂" subunit. Our findings demonstrate that cobalt incorporation significantly impacts the charge distribution and magnetic properties of the thiomolybdate, providing insight into the effects of transition metal uptake at MoS₂ edge sites.