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

摘要

The reaction of a methanolic solution containing the bi-compartmental phenolic ligand 2,6-bis[bis(2-pyridylmethyl) aminomethyl]-4-chlorophenol (LCl-OH) with MCl2 center dot nH(2)O in the presence of NH4PF6 or NaClO4 afforded the dinuclear bridged-phenoxido dichlorido-metal(II) complexes [Co-2(mu-(LO)-O-Cl)(H2O)(2)Cl-2][ Co-2(mu-(LO)-O-Cl)(MeOH)(2)Cl-2](PF6)(2) (1), [Ni-2(mu-(LO)-O-Cl)(MeOH)(2)Cl-2]PF6 (2), [Ni-2(mu-(LO)-O-Cl)(MeOH)(H2O)Cl-2]ClO4 center dot 1.25H(2)O (3), [Cu-2(mu-(LO)-O-Cl)Cl-2] PF6 center dot 1/2MeOH (4) and [Zn-2(mu-(LO)-O-Cl)Cl-2]PF6 center dot 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 vertical bar J vertical bar 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.