А new series of Schiff base Ni(II)4 cubanes: Evaluation of magnetic coupling via carboxylate bridges

Abstract

The Schiff base ligand H2L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction between H2L and Ni(OOCR3)2, R = H in 1, -CH3 in 2, Cl in 3, yielded three new tetranuclear Ni(II) complexes. The complexes have been characterized by elemental analysis, IR- and ES-MS spectroscopy. Their structures as well as structure of ligand were determined by single-crystal X-ray diffraction. Compounds 1-3 possesses tetranuclear cubane-like structures con-taining [Ni4L4(R3COO)2]2- complex anions, which are charge balanced by two triethyl ammonium cati-ons. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridg-ing ligands, is reported for the first time. Variable temperature magnetic susceptibility measurements re-vealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1-3, in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.