Structural, magnetic, and electronic properties of a pentacoordinated intermediate-spin (S = 3/2) iron(III) complex with a macrocyclic [N4]2- ligand

H. Keutel*, I. Käpplinger, E. G. Jäger, M. Grodzicki, V. Schünemann, A. X. Trautwein

*Corresponding author for this work
50 Citations (Scopus)

Abstract

The complex (6,13-bis(ethoxycarbonyl)-5,14-dimethyl-1,4,8,11 -tetraazacyclotetradeca-4,6,12,14-tetraenato(2-))-iron(III) iodide, 3 (chemical formula C18H26O4N4FeI·0.5 C7H8), has been characterized by X-ray crystallography (a = 16.063(3) Å, b = 15.895(3) Å, c = 19.703(4) Å, β = 107.11(3)°; monocline; I2/a; Z = 8), EPR and Mössbauer spectroscopy, and temperature-dependent magnetic susceptibility as well as by MO calculations. The pentacoordinated iron atom is 0.34 Å outside of the [N4] plane. The equatorial Fe-N distances (1.92 Å for the N's in neighborhood of the methylated C-atoms and 1.88 Å for the others) are not significantly different from those found in octahedral low-spin iron(III) complexes with the same macrocyclic [N4 2-] ligand. The magnetic moment (μeff = 4.19μB up to 20 K; Θ = -7.37 K), the EPR measurements (gy eff = 5.38, gx eff = 2.70, and gz eff = 1.74), and the Mössbauer data (δ = 0.18 mm/s, ΔEQ = 3.56 mm/s, T= 120 K) indicate a pure intermediate-spin state of S = 3/2. The MO calculations yield a complete picture of bonding modes, intramolecular interactions, and the electronic structure around the iron center, as indicated by the correct determination of the ground state and by the agreement between the measured and calculated quadrupole splitting.

Original languageEnglish
JournalInorganic Chemistry
Volume38
Issue number10
Pages (from-to)2320-2327
Number of pages8
ISSN0020-1669
DOIs
Publication statusPublished - 01.12.1999

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