SCHEDULED MAINTENANCE
Easy-axis magnetic anisotropy in tetragonally elongated cobalt(ii) complexes beyond the spin-Hamiltonian formalism†
a
Cyril
Rajnák,
*a
Ján
Titiš,
a
Alina
Bieńko,
b
Ján
Moncoľ,
c
Erika
Samoľová
d
and
Roman
Boča
a
Abstract
Two hexacoordinate Co(II) complexes [Co(hfac)2(etpy)2] (1) and [Co(hfac)2(bzpyCl)2] (2) were synthesized and spectrally and structurally characterized. The {CoO4N2} chromophore adopts a geometry of the elongated tetragonal bipyramid with a small o-rhombic component. This less common arrangement causes the magnetic data to need be analysed using the Griffith-Figgis model, instead of the commonly used spin-Hamiltonian with zero-field splitting parameters D and E. In the case of the elongated bipyramid for d7 complexes, the source of the magnetic anisotropy of an easy-axis type is the axial crystal field splitting Δax. The ab initio CASSCF calculations followed by the NEVPT2 module confirm that the ground electronic term is quasi-degenerate owing to the splitting of the 4Eg (D4h) mother term. The lowest spin–orbit multiplets appear as four Kramers doublets belonging to the Γ5 irreducible representation of the double point group D2′. They exhibit a serious mixing of the |±1/2〉 and |±3/2〉 spins which reflects a sizable effect of the spin–orbit coupling. Both complexes exhibit field-supported slow magnetic relaxation governed by the Raman process.
Please wait while we load your content...
