Zig-zag [MnIII4] clusters from polydentate Schiff base ligands

Abstract

Reactions of Schiff base ligands, OH–C6H4–CHNC(R)(CH2OH)2 (R=CH3, H3L1; R=C2H5, H3L2; R=CH2OH, H3L3) with Mn(ClO4)2·6H2O in MeOH solutions afforded MnIII4 complexes, i.e. compounds [Mn4(L1)2(HL1)2(H2O)2(MeOH)2](ClO4)2·yH2O (y=1, 1a·H2O; y=2, 1b·2H2O), [Mn4(L2)2(HL2)2(MeOH)4](ClO4)2 (2a), [Mn4(L2)2(HL2)2(H2O)2(MeOH)2] (ClO4)2·MeOH (2b·MeOH) and [Mn4(L3)2(HL3)2(H2O)4](ClO4)2 (3). The crystal structures of 1a, 1b, 2a and 2b revealed the first examples of MnIII4 complexes consisting of three corner sharing [MnIII2(μ-OR)2] units in trans orientation. The Schiff bases behave as chelating through their phenolato oxygen and imino nitrogen atoms as well as bridging ligands through their deprotonated alkoxo oxygen atoms. In each tetranuclear entity, there are two doubly deprotonated and two triply deprotonated Schiff base ligands which connect two and three metal ions, respectively. Magnetic susceptibility measurements for 2b indicate the interplay of ferromagnetic and antiferromagnetic interactions resulting in a diamagnetic ground state.