Synthesis, crystal structures and magnetic properties of three pentanuclear cyanide-bridged heterometallic complexes

Three dicyanide-containing building blocks and one manganese(III) compound based on bicompartimental Schiff base ligand have been employed to assemble cyanide-bridged heterometallic complexes, resulting in three cyanide-bridged MIII–MnIII (M = Fe, Cr, Co) complexes: K{{[Mn(L)(CH3OH)][Fe(bpb)]}2}ClO4·H2O (1), K{{[Mn(L)(CH3OH)][Cr(bpb)]}2}ClO4·CH3OH (2) and K{{[Mn(L)(CH3OH)][Co(bpb)]}2}ClO4·H2O (3) (bpb2− = 1,2-bis(pyridine-2-carboxamido)benzenate, L = N,N-ethylene-bis(3-methoxysalicylideneiminate). Single X-ray diffraction analysis shows their very similar pentanuclear structures consisting of two same units {[Mn(L)(CH3OH)][Fe(bpb)]} linked by K+ complexed to eight phenolic oxygen atoms. The coordination geometry for both of the M(III) and Mn(III) ion in all the complexes is a slightly distorted octahedron. Investigation over magnetic properties of complexes 1 and 2 reveals the antiferromagnetic magnetic coupling between the neighboring Fe(Cr)(III) and Mn(III) ions through the bridging cyanide group. A best-fit to the magnetic susceptibilities of these two complexes leads to the magnetic coupling constants J = −1.65(2) (1) and −0.99(1) cm−1 (2), respectively.