A Single Thiolate Ligand Modulates the Core Structure and Stability of Non-Magic-Numbered Cadmium-Sulfide Clusters [Cd9S4(SPh)12– x ](2– x )– ( x = 0, 1)

Abstract Semiconductor clusters with magic-numbered compositions have attracted considerable interest as ideal model systems in nanochemistry, whereas those with non-magic-numbered compositions remain poorly understood because of their limited accessibility by wet-chemical synthesis. Here, we generated thiolate-protected cadmium-sulfide clusters with non-magic-numbered compositions, [Cd9S4(SPh)12]2– (Cd9) and [Cd9S4(SPh)11]– (Cd9’), in the gas phase upon electrospray ionization of [Cd10S4(SPh)16](NMe4)4 and investigated the collision-induced dissociation (CID) behaviors. Both Cd9 and Cd9’ yielded the same major dissociation product [Cd8S4(SPh)9]–; however, the dissociation threshold energy for Cd9’ was markedly higher, by ca. 0.3 eV, than that for Cd9. Density functional theory (DFT) calculations revealed that Cd9 retains a highly symmetric pyramidal core closely related to that of the parent magic-numbered cluster, whereas Cd9’ prefers a more distorted core with increased local Cd–S bonds. These results indicate that a difference of one thiolate ligand alters not only the core structure and resistance to dissociation, but also the balance between symmetry-driven and bond-driven stabilization factors. This study highlights ligand coverage as an effective factor for tuning the geometric structure and stability of ligand-protected semiconductor clusters.