Syntheses, structures and magnetism of mixed-valence Mn19 and Mn21 complexes supported by alkylamine-based alkoxo-bridging ligands

Abstract

Two new high-nuclearity mixed-valence Mn clusters, Mn₁₉ and Mn₂₁, were synthesised utilising an alkylamine-based flexible ligand with five alkoxo-bridging groups, 1,3-bis-diethanolamino-2-propanol (H₅bdp). They were obtained from the reaction of Mn(O₂CPh)₂·2H₂O with H₅bdp·2HCl·H₂O and Et₃N in a 4 : 1 : 7 molar ratio in CH₃CN/CH₃OH mixed solution. The X-ray crystal structures revealed {Mn^II₈Mn^III₁₀Mn^IV} and {Mn^II₆Mn^III₁₅} mixed-valence cores composed around {Mn₇O₈} corner-shared double cubanes. Magnetic susceptibility measurements on both complexes indicated dominant intramolecular antiferromagnetic interactions between Mn ions. No clear SMM behaviour was observed above 1.8 K due to the non-parallel alignment of magnetic anisotropy axes of the Mn^III ions.