ИСТИНА

In this report, we discuss recent results of combined experimental characterization and theoretical modeling of several hexa-coordinated Co(II) complexes ((C2H5)4N+[Co(hfac)3-] [1], cis- [Co(hfac)2(H2O)2] [2], [Co(hfac)2BPy], [Co(TDA)(BPy)(H2O)]·4H2O, PipH22+[Co(TDA)2]2-·2H2O, where Hhfac = hexafluoroacetylacetone, BPy = 2,2’-bipyridyl, H2TDA = 2,2’-thiodiacetic acid and Pip = piperazine) synthesized by our group. The analysis of the magnetic anisotropy of these complexes has been based on the use of complimentary experimental techniques such as SQUID magnetometry and EPR spectroscopy accompanied by the theoretical modeling by means of parametrized Griffith Hamiltonian with the set of parameters extracted from the ab initio calculations. The performed analysis revealed essentially triaxial character of the magnetic anisotropy of these complexes with different signs of axial components. The detected frequency dependent AC susceptibility signals show that independently of the sign of axial anisotropy, obtained Co(II) complexes demonstrate a slow paramagnetic relaxation in the presence of DC field, thus belonging to the class of non-uniaxial field induced single ion magnets (SIMs). Such kind of SIM behavior has been assigned to the Kramers character of the Co(II) ion. Along with the Co(II) complexes, we have synthesized and characterized unusual Co(III) complex [CoIII(DiPTU)6](NO3)3 (DiPTU -1,3-diisopropyl-2-thiourea). Although this complex is highly isotropic and does not behave as SIM, it represents unprecedented example of high-spin Co(III) complex with sulfur octahedral coordination.