Magnetic interactions in compounds based on nickel phthalocyanines and pyridine

The nickel(II) complexes of phthalocyanine (four-coordinate, low spin) in pyridine were investigated by EPR spectroscopy and by magnetic susceptibility. The ESR spectra of Ni(II) complexes in frozen (77 K) pyridine solution exhibit well-resolved superhyperfine lines. We attributed this to the formation of six-coordinate high-spin Ni(II) complexes and the interaction of the magnetic moment of the Ni(II) ions with the in-plane and out-of-plane (solvating molecules) nitrogen atoms. Due to the aggragation of molecules, no resolved spectrum could be obtained. The EPR spectrum of the solid-state compound, which was obtained by evaporation of the solution, exhibits a single broad line. The magnetic susceptibility of this compound obeys the Curie-Weiss law with a Weiss constant of θ = −82.9 K. It prefers Ni(↑↑)…N(↓)N(↑)…Ni(↓↓) types of interaction.