A self-assembled octanuclear complex bearing the uncommon close-packed {Fe4Mn4(μ4-O)4(μ-O)4} molecular core

Abstract

A one-pot open-air reaction of manganese powder with iron(II) chloride in DMF solution of the Schiff base (H₂L) formed in situ from salicylaldehyde and hydroxylamine hydrochloride yields the heterometallic complex [Fe₄(μ₄-O)₄Mn₄(L)₈(DMF)₄]·2DMF (1). Single crystal X-ray analysis shows that its molecular structure is based on the octanuclear core {Fe₄Mn₄(μ₄-O)₄(μ-O)₄} with a quite rare molecular structure type {M₈(μ₄-X)₄(μ-X)₄}, where the central cube-like iron motif is modified with four terminal manganese fragments, the whole core being presented as the {Fe₄(μ₄-O)₄} + 4{Mn(μ-O)} combination. Using the data from the Cambridge Structural Database (CSD), an analysis of the octanuclear structures with similar central {M₄(μ₄-X)₄} fragments was performed. The hierarchical order of molecular structure types with the general formula M₈X_n for such compounds was proposed and the topological features as well as the factors that influence the molecular type formation are discussed. Variable-temperature (1.8–300 K) magnetic susceptibility measurements reveal an antiferromagnetic coupling among the magnetic centres in 1.