The Intricate Determination of Magnetic Anisotropy in Quasi-octahedral Vanadium(III): An HF-EPR and Magnetic Study

We report here the synthesis and a preliminary characterization of the tetranuclear complex of formula [Ga 3 V(L Et ) 2 (dpm) 6 ], Ga 3 VEt , in which H 3 L Et = 2-Ethyl-2-(hydroxymethyl)-propane-1,3-diol and Hdpm = dipivaloylmethane , containing a single paramagnetic vanadium(III) center, from a structural, magnetic, and spectroscopic point of view. Structural characterization by X-ray diffraction evidenced that this derivative is isostructural with the star-shaped Single-Molecule Magnet [Fe 3 V(L Et ) 2 (dpm) 6 ], Fe 3 VEt , and can, thus, be considered a model to analyze the magnetic anisotropy of the vanadium(III) ion in that system. The observed results confirm the complexity in obtaining a rationalization of the magnetic behavior of this metal ion, with magnetization data and High Field Electron Paramagnetic Resonance (HF-EPR) spectroscopy providing apparently conflicting results. Indeed, the former were rationalized assuming a rhombic distortion of the ligand field and a dominant easy-axis type anisotropy (equivalent to D ≈ −14.1 cm −1 , E ≈ 1.2 cm −1 ), while a simple axial Spin Hamiltonian approach could explain HF-EPR data (| D | ≈ 6.98 cm −1 ).