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Abstract
The synthesis, structural, and magnetic characterization of five new members of the hexanuclear oximate [MnIII6] family are reported. All five clusters can be described with the general formula [MnIII6O2(R-sao)6(R′-CO2)2(sol)x(H2O)y] (where R-saoH2 = salicylaldoxime substituted at the oxime carbon with R = H, Me and Et; R′ = 1-naphthalene, 2-naphthalene, and 1-pyrene; sol = MeOH, EtOH, or MeCN; x = 0–4 and y = 0–4). More specifically, the reaction of Mn(ClO4)2·6H2O with salicylaldoxime-like ligands and the appropriate carboxylic acid in alcoholic or MeCN solutions in the presence of base afforded complexes 1–5: [Mn6O2(Me-sao)6(1-naphth-CO2)2(H2O)(MeCN)]·4MeCN (1·4MeCN); [Mn6O2(Me-sao)6(2-naphth-CO2)2(H2O)(MeCN)]·3MeCN·0.1H2O (2·3MeCN·0.1H2O); [Mn6O2(Et-sao)6(2-naphth-CO2)2(EtOH)4(H2O)2] (3); [Mn6O2(Et-sao)6(2-naphth-CO2)2(MeOH)6] (4) and [Mn6O2(sao)6(1-pyrene-CO2)2(H2O)2(EtOH)2]·6EtOH (5·6EtOH). Clusters 3, 4, and 5 display the usual [Mn6/oximate] structural motif consisting of two [Mn3O] subunits bridged by two Ooximate atoms from two R-sao2− ligands to form the hexanuclear complex in which the two triangular [Mn3] units are parallel to each other. On the contrary, clusters 1 and 2 display a highly distorted stacking arrangement of the two [Mn3] subunits resulting in two converging planes, forming a novel motif in the [Mn6] family. Investigation of the magnetic properties for all complexes reveal dominant antiferromagnetic interactions for 1, 2, and 5, while 3 and 4 display dominant ferromagnetic interactions with a ground state of S = 12 for both clusters. Finally, 3 and 4 display single-molecule magnet behavior with Ueff = 63 and 36 K, respectively.
Funding
This work was supported by the Operational Programme for Education and Lifelong Learning 2007–2013 (E.P.E.D.V.M.) of the NSRF (2007–2013) [grant number IRAKLITOS II - University of Crete]; which is co-funded by the European Union (European Social Fund) and National Resources.