Synthesis, structure and magnetic properties of homotrinuclear Ni(II) complexes with asymmetric Schiff-base ligands

Abstract

By using 1,3-propanediamine, 2-hydroxyacetophenone and salicylaldehyde an asymmetric ONNO type Schiff base, N(hydroxyphenylidene)-N'(2-hydroxyacetophenylidene)-1,3-propanediamine (H(2)metsalpn), has been prepared and isolated. This Schiff base has been reduced yielding N(2-hydroxybenzyl)-N'[1-(2-hydroxyphenyl)ethyl]-1,3-diaminopropane (H(2)metsalpn(H)) These two ligands were used in preparing three trinuclear Ni(II) complexes with catena-[Ni-3] structural motif, where DMF and carboxylato (formato, acetato, benzoato) ligands occur. These complexes were characterized by EA, IR, TG, DTA and MS data. The X-ray diffraction confirms that the Ni(II) central atoms are in a distorted octahedral coordination environment: the terminal centers possess {NiN2O4} octahedral coordination sphere whereas the very central atom possesses {NiO6} chromophore. The coordinated DMF groups are liberated between 140-240 degrees C. The SQUID magnetometry confirms presence of weak exchange coupling of the antiferromagnetic nature, J/hc = -2 to -7 cm(-1), with a moderate single-ion anisotropy reflected by the zero-field splitting D/hc = +4 to +7 cm(-1). (C) 2014 Elsevier B.V. All rights reserved.