Binuclear cobalt(II/II) and cobalt(II/III) chelates with O₂N₂ ligands: synthesis, structure and magnetic studies

Abstract

The title complexes $[{\text{Co}}^{\text{II}}_{2} {\text{L}}^{ 1}_{2} ]$ and $[{\text{Co}}^{\text{II}} {\text{Co}}^{\text{III}} ( {\text{OAc)L}}^{ 2}_{2} ]$ have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with H₂L¹ and H₂L², respectively, in acetonitrile solution. Here, [L¹]²⁻ and [L²]²⁻ are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of $[{\text{Co}}^{\text{II}}_{2} {\text{L}}^{ 1}_{2} ]$ and $[{\text{Co}}^{\text{II}} {\text{Co}}^{\text{III}} ( {\text{OAc)L}}^{ 2}_{2} ]{\cdot}{\text{H}}_{ 2} {\text{O}}{\cdot}{\text{CH}}_{ 2} {\text{Cl}}_{ 2}$ were determined by x-ray crystallography. In $[{\text{Co}}^{\text{II}}_{2} {\text{L}}^{ 1}_{2} ]$, each cobalt atom has distorted trigonal bipyramid geometry, while in $[{\text{Co}}^{\text{II}} {\text{Co}}^{\text{III}} ( {\text{OAc)L}}^{ 2}_{2} ]$, each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in $[{\text{Co}}^{\text{II}}_{2} {\text{L}}^{ 1}_{2} ]$. The magnetic characterization for $[{\text{Co}}^{\text{II}} {\text{Co}}^{\text{III}} ( {\text{OAc)L}}^{ 2}_{2} ]$ is in agreement with the presence of Co(II) and Co(III) centers.

Graphical Abstract

The title complexes $[{\text{Co}}^{\text{II}}_{2} {\text{L}}^{ 1}_{2} ]$ and $\left[ {\left( {{\text{Co}}^{\text{II}} {\text{Co}}^{\text{III}} } \right){\text{L}}^{ 2}_{2} } \right]$ have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with dianionic N₂O₂ coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III) centers.