Magnetic resonance spectra of some mixed-metal paramagnetic dinuclear complexes with 2-pyridyl methyl ketazine

2-Pyridyl methyl ketazine (PMK) is known to form dinuclear octahedral complexes of formula M2(PMK)3Y4.nH20 (M = Co, Ni, Cu, Zn; Y = Clod, I, BF4). The exchange coupling between the two metal ions appears to be small. We have prepared also solid compounds containing metal complexes of formula MM’(PMK)3(N03)4.3H20 and have recorded the proton magnetic resonance spectra of all the complexes. The isotropic shifts of the ligand protons have been discussed in terms of a simple additive model according to which they are the result of two independent contributions, one from the closer and the other from the farther metal ion. This model allowed us also to assign all the observed signals in the mixed-metal species. Dipolar contributions to the isotropic shifts have been discussed using ESR data. The effect of the two neighboring paramagnetic centers on the signal widths is discussed.