А New Series of Schiff Base Ni(II)4 Cubanes: Evaluation of Magnetic Coupling Via Carboxylate Bridges

Abstract

The Schiff base ligand H 2 L has been synthesized by condensation of 2-aminophenol with 3-methyl-1phenyl-4-formylpyrazol-5-one and reaction between H 2 L and Ni(OOCR 3 ) 2 , R = H in 1, -CH 3 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 containing [Ni 4 L 4 (R 3 COO) 2 ] 2À complex anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubanelike compounds 1-3, in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.