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Inorganics 2018, 6(1), 5; https://doi.org/10.3390/inorganics6010005

Pentacoordinated Chloro-Iron(III) Complexes with Unsymmetrically Substituted N2O2 Quadridentate Schiff-Base Ligands: Syntheses, Structures, Magnetic and Redox Properties

1
Laboratorio de Química Inorgánica y Laboratorio de Cristalografía, Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Campus Curauma, Avenida Universidad 330, Valparaíso, Chile
2
CNRS, University Rennes, ISCR (Institut des Sciences Chimiques de Rennes)—UMR 6226, F-35000 Rennes, France
Present address: Laboratorio de Química-Física, Departamento de Química, Universidad de Antofagasta: Campus Coloso, Avenida Universidad de Antofagasta 02800, Antofagasta, Chile.
*
Authors to whom correspondence should be addressed.
Received: 19 November 2017 / Revised: 22 December 2017 / Accepted: 26 December 2017 / Published: 29 December 2017
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Abstract

Since their development in the 1930s, Schiff-base complexes have played an important role in the field of coordination chemistry. Here, we report the synthetic, spectral, structural, magnetic and electrochemical studies of two new pentacoordinated neutral chloro-iron(III) complexes (3,5) supported by dianionic [N2O2]2− tetradentate Schiff-base ligands unsymmetrically substituted by either a pair of acceptor (F and NO2) or donor (ferrocenyl and OCH3) groups. The electron-withdrawing Schiff-base proligand 2 and the complexes 3 and 5 were prepared in good yields (79–86%). Complex 3 was readily obtained upon reaction of 2 with anhydrous iron chloride under basic conditions, while the bimetallic derivative 5 was synthesized by condensation of the free amino group of the ferrocenyl-containing O,N,N-tridentate half-unit 4 with 5-methoxysalicylaldehyde in the presence of FeCl3. The three new compounds were characterized by elemental analysis, FT-IR, UV–Vis, mass spectrometry and in the case of 2 by multinuclear NMR spectroscopy. The crystal structures of 3 and 5 revealed that in the two five-coordinate monomers, the iron atom showed distorted square-pyramidal geometry, with the N and O atoms of the Schiff-base ligand occupying the basal sites and the chlorine atom at the apex of the pyramid. Magnetic measurements showed a high-spin configuration (S = 5/2) for the Fe(III) ion in 3 and 5. Reduction associated with the Fe(III)/Fe(II) redox couple occurred at −0.464 and −0.764 V vs. Ag/Ag+, and oxidation taking place at the Schiff-base ligand was observed at 1.300 and 0.942 V vs. Ag/Ag+ for 3 and 5, respectively. A high-electronic delocalization of the Schiff-base ligand substituted by fluoro and nitro groups stabilizes the Fe(II) oxidation state and shifts the redox potential anodically. View Full-Text
Keywords: iron; unsymmetrically substituted tetradentate Schiff base; five-coordinate complex; square-pyramidal geometry; magnetism; crystal structure iron; unsymmetrically substituted tetradentate Schiff base; five-coordinate complex; square-pyramidal geometry; magnetism; crystal structure
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Cisterna, J.; Artigas, V.; Fuentealba, M.; Hamon, P.; Manzur, C.; Hamon, J.-R.; Carrillo, D. Pentacoordinated Chloro-Iron(III) Complexes with Unsymmetrically Substituted N2O2 Quadridentate Schiff-Base Ligands: Syntheses, Structures, Magnetic and Redox Properties. Inorganics 2018, 6, 5.

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