Abstract
Synthesis and characterization of structure and magnetic properties of the quasi-octahedral complex (pipH2)[Co(TDA)2] 2H2O (I), (pipH22+ = piperazine dication, TDA2- = thiodiacetic anion) are described. X-ray diffraction studies reveal the first coordination sphere of the Co(II) ion, consisting of two chelating tridentate TDA ligands with a mixed sulfur-oxygen strongly elongated octahedral coordination environment. SQUID magnetometry, frequency-domain Fourier-transform (FD-FT) THz-EPR spectroscopy, and high-level ab initio SA-CASSCF/NEVPT2 quantum chemical calculations reveal a strong "easy-plane" type magnetic anisotropy (D ≈ +54 cm-1) of complex I. The complex shows field-induced slow relaxation of magnetization at an applied DC field of 1000 Oe.
Highlights
For a few decades since the discovery of single molecule magnets (SMMs),[1,2] researchers have sought to obtain polynuclear SMMs with record magnitudes of the spin-inverse barrier (Ueff ) and blocking temperature by increasing the total spin of the molecule.[3,4] contrary to the expectations, the increase of the total molecular spin was unable to give rise to a significant increase of Ueff due to the fact that such increase of the spin leads to a decrease in the absolute value of the axial zero field splitting (ZFS) parameter D,5 which represents the main contribution to the global axial anisotropy of the molecule
The magnetic properties of the complex are determined by a combination of experimental methods SQUID magnetometry, frequency-domain Fourier-transform (FD-FT) THz-EPR spectroscopy, and are in agreement with the results of high-level ab initio SA-CASSCF/NEVPT2 quantum chemical calculations
The data of DC and AC magnetometry analysis, FD-FT THz-EPR spectroscopy, in combination with SA-CASSCF/NEVPT2 calculations show that the complex exhibits a strong easy-plane magnetic anisotropy (D ≈ +54 cm−1) and field-induced slow relaxation of magnetization
Summary
For a few decades since the discovery of single molecule magnets (SMMs),[1,2] researchers have sought to obtain polynuclear SMMs with record magnitudes of the spin-inverse barrier (Ueff ) and blocking temperature by increasing the total spin of the molecule.[3,4] contrary to the expectations, the increase of the total molecular spin was unable to give rise to a significant increase of Ueff due to the fact that such increase of the spin leads to a decrease in the absolute value of the axial zero field splitting (ZFS) parameter D,5 which represents the main contribution to the global axial anisotropy of the molecule. The magnetic properties of the complex are determined by a combination of experimental methods SQUID magnetometry, frequency-domain Fourier-transform (FD-FT) THz-EPR spectroscopy, and are in agreement with the results of high-level ab initio SA-CASSCF/NEVPT2 quantum chemical calculations.
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