A series of mononuclear hexacoordinate iron(III) complexes, [Fe(L-5)(py)]BPh4, and binuclear hexacoordinate iron(III) complexes, [(L-5)Fe(mu(2)-bpy)Fe(L-5)](BPh4)(2), has been prepared and their magnetic properties were investigated; the pentadentate ligands were derivatives of L-5 = 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.