Field-induced SIM behaviour of a Co(II) complex with a 1,1'-diacetylferrocene-derived ligand.

Herein, we report the synthesis and magnetic properties of the Co(ii) coordination compound with the 1,1'-bis(1-((pyrid-2-ylmethylene)hydrazono)ethyl)ferrocene (L) ligand, having the general formula [CoLCl2]. The static magnetic data analysis supported by the CASSCF/NEVPT2 calculations revealed the presence of the triaxial magnetic anisotropy with Dexp = +35.2 cm-1 and large rhombicity (E/D = 0.

Purely Spectroscopic Determination of the Spin Hamiltonian Parameters in High-Spin Six-Coordinated Cobalt(II) Complexes with Large Zero-Field Splitting.

Accurate determination of the spin Hamiltonian parameters in transition-metal complexes with large zero-field splitting (ZFS) is an actual challenge in studying magnetic and spectroscopic properties of high-spin transition metal complexes. Recent critical papers have convincingly shown that previous determinations of these parameters, based only on the magnetic data, have low accuracy and reliability. A combination of X-band electron paramagnetic resonance (EPR) spectroscopy and SQUID magnetometry seems to be a more convincing and accurate approach.

Evidence of field induced slow magnetic relaxation in cis-[Co(hfac)(HO)] exhibiting tri-axial anisotropy with a negative axial component.

We report a combined experimental characterization and theoretical modeling of the hexa-coordinated high-spin Co(ii) complex cis-[Co(hfac)(HO)] (I). The magnetic static field (DC) data and EPR spectra (measurements were carried out on the powder samples of diluted samples cis-[CoZn (hfac)(HO)]) were analyzed with the aid of the parametric Griffith Hamiltonian for the high-spin Co(ii) supported by the ab initio calculations of the crystal field (CF) parameters, g-factors and superexchange parameters between H-bonded Co(ii) ions in the neighboring molecules in a 1D network. This analysis suggests the presence of the easy axis of magnetic anisotropy and also shows the existence of a significant rhombic component.

Single-Ion Magnet EtN[Co(hfac)] with Nonuniaxial Anisotropy: Synthesis, Experimental Characterization, and Theoretical Modeling.

In this article we report the synthesis and structure of the new Co(II) complex EtN[Co(hfac)] (I) (hfac = hexafluoroacetylacetonate) exhibiting single-ion magnet (SIM) behavior. The performed analysis of the magnetic characteristics based on the complementary experimental techniques such as static and dynamic magnetic measurements, electron paramagnetic resonance spectroscopy in conjunction with the theoretical modeling (parametric Hamiltonian and ab initio calculations) demonstrates that the SIM properties of I arise from the nonuniaxial magnetic anisotropy with strong positive axial and significant rhombic contributions.

Theoretical Modeling of the Magnetic Behavior of Thiacalix[4]arene Tetranuclear Mn(II)2Gd(III)2 and Co(II)2Eu(III)2 Complexes.

In view of a wide perspective of 3d-4f complexes in single-molecule magnetism, here we propose an explanation of the magnetic behavior of the two thiacalix[4]arene tetranuclear heterometallic complexes Mn(II)2Gd(III)2 and Co(II)2Eu(III)2. The energy pattern of the Mn(II)2Gd(III)2 complex evaluated in the framework of the isotropic exchange model exhibits a rotational band of the low-lying spin excitations within which the Landé intervals are affected by the biquadratic spin-spin interactions. The nonmonotonic temperature dependence of the χT product observed for the Mn(II)2Gd(III)2 complex is attributed to the competitive influence of the ferromagnetic Mn-Gd and antiferromagnetic Mn-Mn exchange interactions, the latter being stronger (J(Mn, Mn) = -1.

Strong Direct Magnetic Coupling in a Dinuclear Co(II) Tetrazine Radical Single-Molecule Magnet.

The ligand-centered radical complex [(CoTPMA)2 -μ-bmtz(.-) ](O3 SCF3 )3 ⋅CH3 CN (bmtz=3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine, TPMA=tris-(2-pyridylmethyl)amine) has been synthesized from the neutral bmtz precursor. Single-crystal X-ray diffraction studies have confirmed the presence of the ligand-centered radical.

Control of the Barrier in Cyanide Based Single Molecule Magnets Mn(III)2Mn(II)3: Theoretical Analysis.

The aim of this communication is to probe the possibility of increasing the barrier for reversal of magnetization in the family of new cyano-bridged pentanuclear Mn(III)2Mn(II)3 clusters in which single molecule magnet behavior has been recently discovered. In this context, we analyze the global magnetic anisotropy arising from the unquenched orbital angular momenta of ground terms (3)T1(t2(4)) of the two apical Mn(III) ions. The model takes into account the trigonal component of the crystal field, spin-orbit interaction in (3)T1(t2(4)), and an isotropic exchange interaction between Mn(III) and Mn(II) ions.