Synthesis, characterization and magnetic study of two new octahedral iron(III) complexes with pendant zwitterionic Schiff bases

Two Schiff bases, HL1 [2-((3-(dimethylamino)propylimino)methyl)-5-bromophenol] and HL2 [2-((2-(diethylamino)ethylimino)methyl)-6-methoxyphenol], have been employed to prepare two new octahedral iron(III) complexes, [Fe(HL1)2(N3)2]ClO4·2H2O (1) and [Fe(HL2)2(NCS)2]ClO4·H2O (2). Both complexes are characterized by spectral and elemental analyses. Single crystal X-ray diffraction studies confirm their structures. In both complexes, Schiff bases are trapped in their zwitterionic forms and coordinated to iron(III) only through the imine nitrogen and phenoxo oxygen, i.e., they behave as bi-dentate ligands, keeping the remaining potential donor sites pendant. The measurement of χM vs. T for both complexes shows a continuous increase in susceptibility as the temperature decreases. The χM·T values from 300 to 2 K and the shape of these curves for both complexes discard the existence of a high-spin/low-spin transition. The decrease in χM·T of 1 with temperature is more pronounced than that expected for a complex with a small zero-field splitting. The magnetic behavior of 1 is explained by proposing the existence of a physical mixture of S = 5/2 and S = 1/2 spins and the presence of zero-field splitting in the S = 5/2 species.