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

• Asymmetric ONNO type Schiff bases were synthesized and characterized.
• Homotrinuclear NiII–NiII–NiII complexes were synthesized with ONNO type asymmetrical ligands and characterized.
• The magnetic susceptibility and magnetizations of these complexes were measured and explained.
• NiII–NiII–NiII complexes were investigated using thermogravimetry and observed strong exothermic decomposition.

By using 1,3-propanediamine, 2-hydroxyacetophenone and salicylaldehyde an asymmetric ONNO type Schiff base, N(hydroxyphenylidene)-N′(2-hydroxyacetophenylidene)-1,3-propanediamine (H2metsalpn), has been prepared and isolated. This Schiff base has been reduced yielding N(2-hydroxybenzyl)-N′[1-(2-hydroxyphenyl)ethyl]-1,3-diaminopropane (H2metsalpnH) These two ligands were used in preparing three trinuclear Ni(II) complexes with catena-[Ni3] 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 °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.

Asymmetric Schiff-base and its reduced counterpart have been complexes with Ni(II) ions in presence of formato, acetato, and benzoato ions in DMF yielding three catena-[Ni3] complexes whose structures were determined by X-ray diffraction. The SQUID magnetic data confirm presence of the weak exchange interaction of an antiferromagnetic nature, J/hc = −2 to −7 cm−1, along with the moderate zero-field splitting D/hc = +4 to +7 cm−1.Figure optionsDownload as PowerPoint slide