Engineering On‐Surface Spin Crossover: Spin‐State Switching in a Self‐Assembled Film of Vacuum‐Sublimable Functional Molecule

다국어 초록 (Multilingual Abstract)

The realization of spin‐crossover (SCO)‐based applications requires study of the spin‐state switching characteristics of SCO complex molecules within nanostructured environments, especially on surfaces. Except for a very few cases, the SCO of a surface‐bound thin molecular film is either quenched or heavily altered due to: (i) molecule–surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self‐assembly strategy is proposed to fabricate thin spin‐switchable surface‐bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system [Fe(H2B(pz)2)2(bpy)] (pz = pyrazole, bpy = 2,2′‐bipyridine) with a dodecyl (C12) alkyl chain yields a classical amphiphile‐like functional and vacuum‐sublimable charge‐neutral FeII complex, [Fe(H2B(pz)2)2(C12‐bpy)] (C12‐bpy = dodecyl[2,2′‐bipyridine]‐5‐carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiOx surfaces of the complex show comparable spin‐state switching characteristics mediated by similar lamellar bilayer like self‐assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO‐based applications, especially in molecular spintronics.
Self‐assembly and spin crossover go hand in hand, leading to the realization of comparable spin‐state switching characteristics of a pseudoamphiphilic charge‐neutral and vacuum‐sublimable functional SCO complex in bulk and thin film states with implications for the development of large‐area spintronics devices based on SCO complexes.