Structure, magnetic properties, Mossbauer and catalase-like activity of spin crossover iron(III) complexes with salicylaldimine ligands

The preparation and characterization of three new spin-crossover ferric complexes with the composition [Fe(5-Br-Salmeen)(2)]ClO4 (1), [Fe(5-Br-SalEen)(2)]PF6.CH2Cl2 (2), and [Fe(3-OCH3-Salpen)(2)]PF6 (3), where substituted Salmeen, SalEen, and Salpen result from the Schiff-base condensation of substituted salicylaldehyde with N-methylethylenediamine, N-ethylethylenediamine, and N-methylpropylenediamine, respectively. The structural determinations reveal that complexes 1-3 cations possess the same general structure with the N4O2 donor atom set from two tridentate ligands forming a distorted octahedron about the Fe(III) ion. Complexes 1-3 have been shown by variable-temperature magnetic susceptibility (2-300 K) and Fe-57 Mossbauer spectroscopy to be (low-spin, S = 1/2) <-> (high-spin, S = 5/2) spin-equilibrium compounds in the solid state. The H2O2 disproportionation of complexes 1-3 in methanol at 25 degreesC show the rate law of k(obs)[H2O2] [complex].