Systematic Investigation of Controlled Nanostructuring of Mn₁₂ Single-Molecule Magnets Templated by Metal–Organic Frameworks

Abstract

This is the first systematic study exploring metal-organic frameworks (MOFs) as platforms for the controlled nanostructuring of molecular magnets. We report the incorporation of seven single-molecule magnets (SMMs) of general composition [Mn₁₂O₁₂(O₂CR)₁₆(OH₂)₄], with R = CF₃ (1), (CH₃)CCH₂ (2), CH₂Cl (3), CH₂Br (4), CHCl₂ (5), CH₂Bu^t (6), and C₆H₅ (7), into the hexagonal channel pores of a mesoporous MOF host. The resulting nanostructured composites combine the key SMM properties with the functional properties of the MOF. Synchrotron-based powder diffraction with difference envelope density analysis, physisorption analysis (surface area and pore size distribution), and thermal analyses reveal that the well-ordered hexagonal structure of the host framework is preserved, and magnetic measurements indicate that slow relaxation of the magnetization, characteristic of the corresponding Mn₁₂ derivative guests, occurs inside the MOF pores. Structural host-guest correlations including the bulkiness and polarity of peripheral SMM ligands are discussed as fundamental parameters influencing the global SMM@MOF loading capacities. These results demonstrate that employing MOFs as platforms for the nanostructuration of SMMs is not limited to a particular host-guest system but potentially applicable to a multitude of other molecular magnets. Such fundamental findings will assist in paving the way for the development of novel advanced spintronic devices.