Structure-Induced Spin Switching in Triple-Decker Metal-Ring-Metal Nanoclusters

Controlling the spin state of single molecules is central to the next-generation molecular electronics and spintronic architectures. Using first-principles computational methods, we systematically investigate the geometrical, electronic structures, magnetic properties, and transport behaviors of the sandwich-like [Cp-M(cyclo-E₅)M-Cp]^x (E = Sb, Bi; M = V, Ta, Nb) nanoclusters (NCs), which feature a unique "metal-ring-metal" topology. We demonstrate that mechanical perturbations─specifically the vertical translation and in-plane rotation of the central E₅ ring─ effectively modulate the localized coordination field to enable robust, reversible high-spin to low-spin (HS ↔ LS). Moreover, in specific oxidation states, these distinct spin states are coupled with unique magnetic correlations, where the HS state exhibits ferromagnetic (FM) alignment and the LS state manifests antiferromagnetic (AFM) coupling. Crucially, the rotational dynamics of the central ring realize a temperature-dependent, conformationally switchable magnetic phase, while electronic charge modulation provides a highly sensitive, orthogonal axis for gating these magnetic characteristics. These combined mechanical and electrical degrees of freedom yield highly distinctive magnetic signatures and spin-polarized electronic transport profiles. By mapping out specific candidate molecules, highlighting the antimony-based [Cp-V(cyclo-Sb₅)V-Cp]^x NCs framework as an exceptional candidate for multimode mechanical control, our findings deliver a rigorous, structure-driven blueprint for molecular spin regulation, positioning this class of nanoclusters as highly promising platforms for single-molecule memory, nanoscale spin valves, and molecular spintronic applications.