Achieving Ambient‐Temperature Multiway Bistability via Electron‐Transfer‐Coupled Spin‐State Switching in 2D Hexagonal Materials

ABSTRACT Magnetic materials exhibiting bistability under ambient conditions are highly attractive for applications in data‐storage, memory devices, sensors, and stimuli‐responsive technologies. Cyanide‐bridged octacyanometallates provide a uniquely versatile platform for constructing molecular architectures with tunable electronic and magnetic properties. Here, we present two structurally related cyanide‐bridged 2D hexagonal [W─Co] networks that combine structural adaptability with multifunctional switching. Complex 1 {[W(CN) ₈ ] ₂ [Co(V‐im) ₄ ] ₃ } _n , undergoes a rare single‐crystal‐to‐single‐crystal (SC‐SC) transformation to yield complex 2 {[W(CN) ₈ ] ₂ [Co(V‐im) ₄ ] ₂ [Co(V‐im) ₂ (DMF) ₂ ].4H ₂ O} _n , enabling a direct structure‐property correlation within the same material system. Complex 1 displays a reversible, single‐step, thermally induced metal‐to‐metal electron transfer (MMET), while complex 2 exhibits a two‐step MMET process operating near ambient temperature. Both complexes further demonstrate light‐induced bistability: near‐infrared irradiation (808, 900 nm) drives conversion of the diamagnetic {W ^IV _LS ‐CN‐Co ^III _LS } ground state to a metastable paramagnetic {W ^V _LS ‐CN‐Co ^II _HS } state, which is reversibly switched OFF by visible‐light irradiation (405, 635 nm). The bistability is unambiguously established by combining variable‐temperature magnetic susceptibility, photomagnetic measurements, and synchrotron x‐ray absorption spectroscopy, which directly probes the local electronic reorganization at W and Co centers. This work demonstrates how molecular engineering of cyanide‐bridged 2D frameworks can deliver robust, multi‐stimuli‐responsive bistable materials that operate close to room temperature, offering a promising platform for molecular spintronics and optoelectronic devices.