Publication in Inorganic Chemistry

The aim of the work was to reveal the impact of axial ligands on the magnetic anisotropy of pentagonal-bipyramidal mononuclear Co(II) complexes with general formula [Co(L)X2], where L is a 15-membered pentadentate pyridine-based macrocycle and X is monodentate halogenido ligand (Cl, Br, I). The thorough analyses of the magnetic data revealed a large easy-plane type of the magnetic anisotropy (D > 0) for all three compounds, with the D-values (axial zero field splitting parameter) increasing in the order 35 cm−1 (I), 38 cm−1 (Cl), and 41 cm−1 (Br). Various theoretical methods like the Angular Overlap Model, density functional theory, CASSCF/CASPT2, CASSCF/NEVPT2 were utilized in order to understand the observed trend in magnetic anisotropy. The D-values correlated well with the Mayer bond order (decreasing in order Co−I > Co−Cl > Co−Br), which could be a consequence of two competing factors: (a) the ligand field splitting and (b) the covalence of the Co−X bond. All the complexes also behave as field-induced single-molecule magnets with the Raman relaxation process most likely responsible for the slow relaxation of the magnetization. The results of the work revealed that the previously suggested and fully accepted strategy employing heavier halogenido ligands in order to increase the magnetic anisotropy has some limitations in the case of pentagonal−bipyramidal CoII complexes.

 

 

 

 

Date: 13. apr 2017 | Author: agch

Department of Inorganic Chemistry

Faculty of Science
Palacký University in Olomouc

17. listopadu 12
CZ-771 46 Olomouc
Czech Republic

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email : agch(at)upol.cz