Spin crossover in mononuclear and binuclear iron(III) complexes with pentadentate Schiff-base ligands

A series of mononuclear hexacoordinate iron(III) complexes, [Fe(5L)(py)]BPh4, and binuclear hexacoordinate iron(III) complexes, [(5L)Fe(μ2-bpy)Fe(5L)](BPh4)2, has been prepared and their magnetic properties were investigated; the pentadentate ligands were derivatives of 5L=saldptn=N,N′-bis(2-hydroxybenzyliden)-1,7-diamino-4-azaheptane. Temperature variation of the effective magnetic moment for them shows that a spin transition from the low-spin to the high-spin state occurs. The magnetic data were fitted to an Ising-like model appropriate for the mono- and binuclear systems.