Abstract
The Schiff base ligand H 2 L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction with Ni(OOCR 3 ) 2 , R = H in 1 , -CH 3 in 2 , Cl in 3 , to yield three new tetranuclear Ni(II) complexes The ligands and the complexes have been characterized by elemental analysis, IR- and NMR- spectroscopy. Their structures 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 ] 2- complex as 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 cubane-like compounds 1-3 , in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.
Highlights
Tetranuclear cubane-like M4O4 complexes including high-spin cobalt(II) and nickel(II) metal centers have been a very important class of molecules due to their potential application as a new type of magnetic materials [1,2]
This is apparently helpful for the synthesis of new molecular magnets allowing preparation of the Co(II) or Ni(II) cubanes with the dominant ferromagnetic interactions among the metal centers and non-negligible magnetic anisotropy of the ground state
None of them possessed the cubane like structure and here we present the first Ni cubane compound bridged by trichloroacetate ligand
Summary
Tetranuclear cubane-like M4O4 complexes including high-spin cobalt(II) and nickel(II) metal centers have been a very important class of molecules due to their potential application as a new type of magnetic materials [1,2]. The structure of the cubane cores can be modified by introducing alterations in the coordinating ligands and the change in crystallization conditions such as solvent, temperature, guest molecules and pH [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] This is apparently helpful for the synthesis of new molecular magnets allowing preparation of the Co(II) or Ni(II) cubanes with the dominant ferromagnetic interactions among the metal centers and non-negligible magnetic anisotropy of the ground state. We present a detailed magnetic study explaining the observed unexpected magnetic behavior of complexes in correlation to their structures
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