Structural and magnetic studies of the [Mn12O12(CH3COO)16(H2O)4]·2CH3COOH·4H2O thermal derivatives

Abstract

Thermal transformations of the well-known high spin manganese carboxylate cluster [Mn₁₂O₁₂(CH₃COO)₁₆(H₂O)₄]·4H₂O·2CH₃COOH have been studied in detail. Three steps in its thermal transformation have been observed with the successive formation of well-defined compounds. Upon heating at 403 K, acetic acid and water molecules located in inter-cluster void spaces are removed without significant modification of the structural packing and magnetic properties. Interestingly, the resulting material presents the remarkable property of being able to incorporate ammonia into its structure. Dramatic changes in the magnetic properties of this insertion compound have been observed and confirmed the first synthesis of a single-molecule magnet material by gas inclusion. Further heating at 513 K stabilizes the hausmannite Mn₃O₄ phase as indicated by X-ray diffraction, thermogravimetric analyses and magnetic measurements. Finally, heating of the compound above 573 K leads to a mixture of different manganese compounds, Mn₃O₄ and MnCO₃, previously observed in the decomposition of Mn(CH₃COO)₂·4H₂O.