Manganese clusters of aromatic oximes: synthesis, structure and magnetic properties

Abstract

With the aim of tuning the structures by using oxime ligands with different non-coordinating groups, three aromatic oxime ligands were designed by fusing oxime groups (N–OH) onto different non-coordinating groups. Their reactions with the corresponding Mn(II) salts gave five manganese clusters [Mn^III₃(μ₃-O)(L¹)₃(DMF)(H₂O)₃Cl]·2DMF·CH₃OH (1), [Mn^III₃(μ₃-O)(L²)₃(OAc)(CH₃OH)₂] (2), [Mn^III₆(μ₃-O)₂(L²)₆(H₂O)(py)₇](ClO₄)₂·py·0.5CH₃OH·2H₂O (3), [Mn^III₈O₄(L²)₈(DMF)₄]·DMF·6CH₃CN (4), and [Mn^II₄Mn^III₄O₄(L³)₁₂]·3DMF·6H₂O (5), in which H₂L¹, H₂L² and HL³ represent indane-1,2,3-trione-1,2-dioxime, acenaphthenequinone dioxime, and 9,10-phenanthrenedione-9-oxime, respectively. Their structures were determined and studied in detail. 1 and 2 show planar triangular trinuclear Mn^III₃ structures. 3 has a hexanuclear Mn^III₆ skeleton formed from two Mn^III₃ triangular units through inter-trinuclear mutual coordination. 4 and 5 present octanuclear skeletons constructed from planar triangular Mn₃O and tetrahedral Mn₄O secondary building units, respectively, with different symmetries and different oxidation states of the manganese ions. Their structural studies reveal a significant contribution of the parent rings for fusing oxime groups, different non-coordinating groups and anions to the formation of different cluster skeletons. Their magnetic properties were investigated and simulated, which revealed the presence of dominant antiferromagnetic interactions between the metal ions in these compounds.