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.

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. The detected frequency dependent (AC) susceptibility signal shows that complex I exhibits slow paramagnetic relaxation in the applied DC field belonging thus to the class of non-uniaxial field induced single ion magnets with a negative axial component of anisotropy. It is demonstrated that the main contributions to the relaxation come from the direct one-phonon process dominating at low temperatures, while the contribution of the two-phonon Raman process becomes important with increasing temperature.

A molecular magnetic (C 25 H 23 N 3 O 3 Cl)CrMn(C 2 O 4 ) 3 •H 2 O whose spiropyran cation con tains a quaternized pyridine fragment in the side aliphatic chain was synthesized for the first time. The compound possesses the properties of a ferromagnetic with T c = 5.2 K and photo chromic properties in the crystalline state. The photochemical properties of the hybrid com pound were studied by electronic and IR spectroscopies. Photochromic transformations of the spiropyran cation are accompanied by the appearance of a broad absorption band in the region 400-600 nm in the electronic spectra and by reduction of intensity of the ν(C spiro -O) IR band at 942 cm -1 .

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