Synthesis, structural investigations and magnetic properties of dipyridinated manganese phthalocyanine, MnPc(py) 2

Abstract

The MnPc(py) 2 complex was obtained in the reaction of MnPc with purified and dry pyridine under non-oxidation conditions. It crystallises in the centrosymmetric space group P2 1/ c of the monoclinic system with two molecules per unit cell. The Mn 2+ cation is coordinated by four N-isoindole atoms of phthalocyaninato(2−) macrocycle and axially by two nitrogen atoms of pyridine molecules into a tetragonal bipyramid. The MnPc(py) 2 crystals are moderately stable under air, but in pyridine solution the MnPc(py) 2 complex undergoes oxidation by O 2 yieldings the binuclear manganese(III) μ-oxo complex (MnPcpy) 2O as evidenced by the UV–Vis spectroscopy. The magnetic susceptibility measurement performed on solid sample of MnPc(py) 2 shows the Curie–Weiss behaviour in the temperature region of 300–15 K. The calculated magnetic moment μ eff indicates three unpaired electrons ( S=3/2), thus the ground state configuration of Mn ion is (a 1g) 2(e g) 2(b 2g) 1, and the MnPc(py) 2 complex is the intermediate spin complex. Below 5.5 K ( T N) the magnetic susceptibility sharply decreases due to the cooperative intermolecular antiferromagnetic interactions.