Magnetic and structural properties of dinuclear singly bridged-phenoxido metal(ii) complexes

Abstract

The reaction of a methanolic solution containing the bi-compartmental phenolic ligand 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenol (L^Cl-OH) with MCl₂·nH₂O in the presence of NH₄PF₆ or NaClO₄ afforded the dinuclear bridged-phenoxido dichlorido-metal(II) complexes [Co₂(μ-L^ClO)(H₂O)₂Cl₂][Co₂(μ-L^ClO)(MeOH)₂Cl₂](PF₆)₂ (1), [Ni₂(μ-L^ClO)(MeOH)₂Cl₂]PF₆ (2), [Ni₂(μ-L^ClO)(MeOH)(H₂O)Cl₂]ClO₄·1.25H₂O (3), [Cu₂(μ-L^ClO)Cl₂]PF₆·1/2MeOH (4) and [Zn₂(μ-L^ClO)Cl₂]PF₆·MeOH (5). The complexes were characterized by elemental microanalyses, conductivity measurements, IR and UV-Vis spectroscopy, mass spectrometry and single crystal X-ray crystallography. Each M(II) center within the dinuclear complex cations is octahedrally coordinated in complexes 1–3, and five-coordinated distorted square pyramidal in 4 and 5. Magnetic susceptibility measurements at variable temperature of the complexes 1–4 revealed weak to moderate antiferromagnetic coupling with |J| values = 8.38, 39.0, 30.2 and 0.79 cm⁻¹, respectively. The results of DFT calculations correlate well with the experimentally determined antiferromagnetic coupling and show that the magnetic exchange coupling occurs mainly through the phenoxido bridge M–O–M. Implications of geometry around the central metal ion, M⋯M distance, M–O–M bond angle and overlapping of magnetic orbitals on the magnetic exchange coupling are discussed.