Synthesis and characterization of a mononuclear iron(III) complex with a tripodal triamide ligand

Abstract

A new potentially heptadentate tripodal ligand has been synthesized by the condensation reaction between tris(2-aminoethyl)amine and acetylsalicyclic acid in a 1:3 molar ratio. The o-acetyl linkage is cleaved by treating with KOH to form the desired ligand with the donors that include three amide nitrogens, three phenolate oxygens and one bridgehead nitrogen. Fe(acac)₃ readily forms a dark red 1:1 complex with the ligand. The complex behaves as a non-electrolyte in acetonitrile. The electronic absorption spectrum in the visible region is dominated by a strong absorption with λ _max at 425 nm, assignable to an LMCT transition from phenolate oxygen to iron(III) in an octahedral coordination geometry. The magnetic moment value at room temperature (5.5 μ _eff/μ _g) and the EPR spectra in the solid state and in solution (g = 4.06) are consistent with high-spin rhombically distorted octahedral iron(III). Room-temperature Mössbauer data provide the following values: isomer shift 0.37 mm s⁻¹ and quadrupole splitting 0.82 mm s^8722;1. These data are consistent with a discrete, high-spin octahedral iron(III) complex.