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Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy

Technologies for mass production require cheap and abundant materials such as ferrous chloride (FeCl(2)). The literature survey shows the lack of experimental studies to validate theoretical conclusions related to the population of ionic Fe-species in the aqueous FeCl(2) solution. Here, we present a...

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Autores principales: Luin, Uroš, Arčon, Iztok, Valant, Matjaz
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8839570/
https://www.ncbi.nlm.nih.gov/pubmed/35163907
http://dx.doi.org/10.3390/molecules27030642
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author Luin, Uroš
Arčon, Iztok
Valant, Matjaz
author_facet Luin, Uroš
Arčon, Iztok
Valant, Matjaz
author_sort Luin, Uroš
collection PubMed
description Technologies for mass production require cheap and abundant materials such as ferrous chloride (FeCl(2)). The literature survey shows the lack of experimental studies to validate theoretical conclusions related to the population of ionic Fe-species in the aqueous FeCl(2) solution. Here, we present an in situ X-ray absorption study of the structure of the ionic species in the FeCl(2) aqueous solution at different concentrations (1–4 molL(−1)) and temperatures (25–80 °C). We found that at low temperature and low FeCl(2) concentration, the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33 (±0.02) Å and five water molecules at a distance of 2.095 (±0.005) Å. The structure of the ionic complex gradually changes with an increase in temperature and/or concentration. The apical water molecule is substituted by a chlorine ion to yield a neutral Fe[Cl(2)(H(2)O)(4)](0). The observed substitutional mechanism is facilitated by the presence of the intramolecular hydrogen bonds as well as entropic reasons. The transition from the single charged Fe[Cl(H(2)O)(5)](+) to the neutral Fe[Cl(2)(H(2)O)(4)](0) causes a significant drop in the solution conductivity, which well correlates with the existing conductivity models.
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spelling pubmed-88395702022-02-13 Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy Luin, Uroš Arčon, Iztok Valant, Matjaz Molecules Article Technologies for mass production require cheap and abundant materials such as ferrous chloride (FeCl(2)). The literature survey shows the lack of experimental studies to validate theoretical conclusions related to the population of ionic Fe-species in the aqueous FeCl(2) solution. Here, we present an in situ X-ray absorption study of the structure of the ionic species in the FeCl(2) aqueous solution at different concentrations (1–4 molL(−1)) and temperatures (25–80 °C). We found that at low temperature and low FeCl(2) concentration, the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33 (±0.02) Å and five water molecules at a distance of 2.095 (±0.005) Å. The structure of the ionic complex gradually changes with an increase in temperature and/or concentration. The apical water molecule is substituted by a chlorine ion to yield a neutral Fe[Cl(2)(H(2)O)(4)](0). The observed substitutional mechanism is facilitated by the presence of the intramolecular hydrogen bonds as well as entropic reasons. The transition from the single charged Fe[Cl(H(2)O)(5)](+) to the neutral Fe[Cl(2)(H(2)O)(4)](0) causes a significant drop in the solution conductivity, which well correlates with the existing conductivity models. MDPI 2022-01-19 /pmc/articles/PMC8839570/ /pubmed/35163907 http://dx.doi.org/10.3390/molecules27030642 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Luin, Uroš
Arčon, Iztok
Valant, Matjaz
Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy
title Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy
title_full Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy
title_fullStr Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy
title_full_unstemmed Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy
title_short Structure and Population of Complex Ionic Species in FeCl(2) Aqueous Solution by X-ray Absorption Spectroscopy
title_sort structure and population of complex ionic species in fecl(2) aqueous solution by x-ray absorption spectroscopy
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8839570/
https://www.ncbi.nlm.nih.gov/pubmed/35163907
http://dx.doi.org/10.3390/molecules27030642
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