Ferromagnetic interaction in iron(II)-bis-Schiff base complexes

The preparation and magnetic properties of three Fe(II)-bis-Schiff base complexes, [Fe-2(L1)2(4,4'-bpy)]center dot MeOH (1), [Fe(L2)(EtOH)] (2) and [Fe(L3)(MeOH)] (3) (L1 =N,N'-bis(2-hydroxy-1-naphthaldehyde)-1,2-phenylenediimine; L2 = N,N'-bis(salicylidene)-1,2-phenylenediamine; L3 = N,N'-bis(5-Cl-salicylidene)-1,2-phenylenediamine; 4,4'-bpy = 4,4'-bipyridine) are reported. X-ray single crystal structure analyses for 1-3 reveal that 1 shows a dinuclear Fe(II)-bis-Schiff base complex bridged by 4,4'-bpy, while 2 and 3 show mononuclear structures. Molecular packing of 2 shows a uniform one-dimensional chain structure through hydrogen bonds and Fe center dot center dot center dot pi interaction and that of 3 indicates significant pi-pi interaction to form a dimmer structure. The chi T-T plots of 1-3 show all ferromagnetic interaction at low temperature. The origin of the ferromagnetic interaction observed in 2 is tentatively ascribed to the dimer formation through Fe center dot center dot center dot pi interaction at low temperature. (C) 2008 Elsevier Ltd. All rights reserved.