Synthesis, structure, and magnetic properties of dicopper and tricobalt complexes based on N-(2-pyridylmethyl)iminodiethanol

Abstract

Dinuclear [Cu(H₂pmide)(NO₃)Cu(Hpmide)](NO₃)₂ (1) and trinuclear [(pmide)₂Co₃(CH₃CO₂)₂(NCS)₂]·4CH₃OH (2) coordination complexes have been prepared by the reaction of the tetradentate H₂pmide ligand and Cu(NO₃)₂·3H₂O or Co(CH₃CO₂)₂·4H₂O/NaNCS in organic solvent (H₂pmide = N-(2-pyridylmethyl)iminodiethanol). In 1, one copper(II) ion is bonded with a H₂pmide, and the other is coordinated with a mono-deprotonated Hpmide⁻. The copper(II) ions are linked through an ethoxo group of the Hpmide⁻ ligand and two oxygen atoms of a nitrate ion, resulting in an asymmetric dinuclear structure. In 2, two terminal cobalt(III) units are coordinated with pmide²⁻, NCS⁻, and CH₃CO₂⁻. The terminal units are each connected to a central cobalt(II) cation through the two oxygen atoms of pmide²⁻ and one bridged acetate ion, giving rise to a mixed-valence trinuclear cobalt complex formulated as Co^III–Co^II–Co^III. Complex 1 shows a strong antiferromagnetic interaction through the ethoxo and nitrato groups between the copper(II) ions [g = 2.070, J = –88.1 cm⁻¹ (–61.2 K)]. However, complex 2 behaves as a paramagnetic cobalt(II) monomer, due to the diamagnetic cobalt(III) ions in the terminal units [g = 2.526, |D| = 51.8 cm⁻¹ (36.0 K)].