| 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 andMössbauer spectroscopy, and temperature-dependent magnetic susceptibility as well as by MO calculations. Thepentacoordinated iron atom is 0.34 Å outside of the [N4] plane. The equatorial Fe−N distances (1.92 Å for theN's in neighborhood of the methylated C-atoms and 1.88 Å for the others) are not significantly different fromthose found in octahedral low-spin iron(III) complexes with the same macrocyclic [N42-] ligand. The magneticmoment (μeff = 4.19 μB up to 20 K; ϑ = −7.37 K), the EPR measurements (gyeff = 5.38, gxeff = 2.70, and gzeff= 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 stateand by the agreement between the measured and calculated quadrupole splitting.
- The iron(III) complex with a non-porphyrin [N4]2- macrocycle and axial iodide was characterized as a pentacoordinated complex with pure intermediate-spin state by X-ray crystallography and EPR and Mössbauer spectroscopy as well as magnetic measurements. MO calculations yield a complete picture of the bonding modes and the electronic structure.
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