Synthesis, structural and magnetic properties of cobalt(ii) complexes with pyridine-based macrocyclic ligand containing two pyridine pendant arms

Abstract

With the aim of tuning the magnetic anisotropy, a series of Co(II) complexes with the general formula of complex cations [Co(L)X]⁺, where X = Br⁻ (1); I⁻ (2); NCO⁻ (3); NCS⁻ (4a); N₃⁻ (5), and [Co(L)(NCS)₂] (4b), (L = a 17-membered pyridine-based N₃O₂-macrocyclic ligand containing two pyridin-2-ylmethyl pendant arms) were prepared and thoroughly characterized. The molecular structures for all complexes showed strongly distorted geometry in between octahedral and trigonal prismatic. The magnetic studies confirmed substantial magnetic anisotropy with positive values of D, the axial zero-field splitting parameter, but E/D ratios close to 1/3. This was supported by theoretical CASSCF calculations showing no significant effect of the co-ligands. Complex 4b was found to behave as a field-induced SMM.