Probing the Influence of Structural Distortion and Axial Ligands on Magnetic Anisotropy in a Series of Chiral Pentagonal Bipyramidal Co(II) and Ni(II) Complexes

Abstract

A series of magnetically anisotropic chiral pentagonal bipyramidal (PBP) Co(II) and Ni(II) complexes are prepared by employing chiral bis-hydrazone ligands, viz., 2,6-diacetylpyridinebis(R/S-lactic acid hydrazide) (R,R/S,S-daplh) and (R)/(S)-2, 6-diacetylpyridinebis(3-hydroxyisobutyric acid hydrazide) (R,R/S,S-daphibh). Investigations of magnetic anisotropy by wave function based ab initio CASSCF calculations manifest the presence of substantial negative uniaxial magnetic anisotropy in the present PBP Ni(II) complexes, while the chiral PBP Co(II) complexes display large easy-plane magnetic anisotropy. Magnetostructural correlations show the profound influence of structural distortions and the ligand field environment on the axial zero field splitting parameter (D). Accordingly, a convenient strategy to enhance the D parameter in PBP Co(II) and Ni(II) complexes is devised.