Synthesis and Magnetic Properties of Iron(III) Complexes with Several Quadridentate Schiff Bases

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Abstract
New iron(III) complexes containing quadridentate Schiff bases, [Fe(L)AB]n+, were prepared, where H2L represents a quadridentate Schiff base, and A and B, unidentate ligands, such as imidazole, pyridine derivatives, and cyanide ions. The magnetic moments of the complexes are in the range of 1.9–6.0 B.M. at room temperature. Based on the magnetic susceptibilities at various temperatures (90–295 K), these compleses were classified into four types: (1) high-spin (S=5⁄2), (2) low-spin (S=1⁄2), (3) intermediate spin (S=3⁄2), and (4) cross-over complexes, the last of which have a ligand-field strength near the cross-over point of high-spin and low-spin types. From the ESR spectra obtained, the existence of a spin-equilibrium was established for the cross-over complexes.