Lithium recognition reconfigures a multistep spin-crossover pathway in a crown ether-functionalized Hofmann-type framework

Chemically addressable bistable magnetic materials require molecular recognition events that do more than shift a transition temperature—they must reconfigure the underlying switching pathway. Here we report a crown ether-functionalized Hofmann-type framework, {Fe(DPy-B12C4)[Ag(CN)₂]₂}·2CH₂Cl₂ (1·2CH₂Cl₂), that couples Li⁺ recognition to a pronounced reorganization of multistep spin crossover (SCO). The pristine framework exhibits guest-dependent multistep switching, whereas Li⁺ uptake selectively suppresses the higher-temperature branch of the original transition and drives the magnetic response toward a single dominant switching event in a loading-dependent and reversible manner. Spectroscopic data support specific Li⁺ coordination at the crown ether site, while structural and magnetic analyses indicate that ion binding reduces local conformational heterogeneity and perturbs the cooperative elastic/electronic landscape governing spin-state interconversion. This work establishes ion recognition as a chemically selective means to reconfigure cooperative SCO pathways and identifies crown ether-functionalized Hofmann-type frameworks as a platform for ion-responsive bistable magnetic materials.