Abstract
We report here the synthesis and a preliminary characterization of the tetranuclear complex of formula [Ga3V(LEt)2(dpm)6], Ga3VEt, in which H3LEt = 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 [Fe3V(LEt)2(dpm)6], Fe3VEt, 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).
Highlights
The discovery in the early 90s of Single-Molecule Magnet (SMM) behavior, i.e., magnetic bistability at the molecular level in polynuclear transition metal complexes [1], sparked intense research in the field of molecular magnetism, aiming at the possible use of these systems as magnetic memory units [2]
It is first to be noted that the analysis of magnetic and High Field Electron Paramagnetic Resonance (HF-EPR) data provides conflicting indications: for the first set of techniques, the results can only be rationalized by assuming that vanadium(III) in Ga3VEt has easy-axis type anisotropy, and its global behavior cannot be traced back to a simple spin triplet, but rather to a 3E ligand field state partially split by rhombic distortion
We have reported a preliminary characterization of a Ga3VEt cluster both from a structural, magnetic, and spectroscopic point of view
Summary
The discovery in the early 90s of Single-Molecule Magnet (SMM) behavior, i.e., magnetic bistability at the molecular level in polynuclear transition metal complexes [1], sparked intense research in the field of molecular magnetism, aiming at the possible use of these systems as magnetic memory units [2]. When thermal energy is much lower than the height of the barrier, a system previously magnetized will retain its magnetization; on the contrary, on increasing temperature, thermal energy becomes large enough to allow fast relaxation of the magnetization, leading to a loss of the information stored in it This prompted many groups to find ways to improve the magnetic anisotropy barrier rationally [4, 5]. This is, by no means a simple task: in polynuclear clusters, it requires careful engineering of the anisotropic features of the constituent ions, the relative orientation of their magnetic anisotropy axis, and the exchange coupling among the centers [6].
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