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Chemphyschem ; 20(8): 1001-1005, 2019 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-30897255


Herein, we report a new trigonal prismatic cobalt(II) complex that behaves as a single molecule magnet. The obtained zero-field splitting, which is also directly accessed by THz-EPR spectroscopy (-102.5 cm-1 ), results in a large magnetization reversal barrier U of 205 cm-1 . Its effective value, however, is much lower (101 cm-1 ), even though there is practically no contribution from quantum tunneling to magnetization relaxation.

ACS Omega ; 3(5): 4941-4946, 2018 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-31458710


Variable-temperature NMR spectroscopy has recently emerged as a new alternative to the magnetometry methods for studying single molecule magnets. Its use is based on an accurate determination of magnetic susceptibility tensor anisotropy Δχ, which is not always achievable due to some contact contribution to NMR chemical shifts and possible conformational dynamics. Here, we applied this approach to cholesteryl-substituted cage cobalt(II) complexes featuring a very large magnetic anisotropy. Conformational rigidity and large size of the cholesteryl substituent with many magnetically nonequivalent nuclei resulted in an excellent convergence of experimental and calculated 1H and 13C chemical shifts, thus allowing for the determination of Δχ value for all of the synthesized cobalt(II) complexes with a very high accuracy and providing a more reliable zero-field splitting energy for further calculations.

Inorg Chem ; 56(12): 6943-6951, 2017 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-28541691


High magnetic anisotropy is a key property of paramagnetic shift tags, which are mostly studied by NMR spectroscopy, and of single molecule magnets, for which magnetometry is usually used. We successfully employed both these methods in analyzing magnetic properties of a series of transition metal complexes, the so-called clathrochelates. A cobalt complex was found to be both a promising paramagnetic shift tag and a single molecule magnet because of it having large axial magnetic susceptibility tensor anisotropy at room temperature (22.5 × 10-32 m3 mol-1) and a high effective barrier to magnetization reversal (up to 70.5 cm-1). The origin of this large magnetic anisotropy is a negative value of zero-field splitting energy that reaches -86 cm-1 according to magnetometry and NMR measurements.