Incommensurate crystal structure, thermal expansion study and magnetic properties of (dimethylimidazolium)2[Fe2Cl6(?-O)]

A thorough characterization of the title compound, (dimim)2[Fe2Cl6(µ-O)], consisting of a (µ-oxido)-bridged binuclear iron(III) complex and 1,3-dimethylimiazolium (dimim) cation, has been performed using a wide range of techniques. The room temperature disordered crystal structure of this compound transits to an incommensurately modulated crystal structure at 100 K; to our knowledge, the first one found for an imidazolium halometallate complex. The crystal structure was solved in the superspace group PĪ(/α/β/γ)0 with modulation vector q=0.1370(10) 0.0982(10) 0.326(2) at 100 K. Variable temperature synchrotron powder x-ray diffraction showed the presence of satellite peaks in addition to the main diffraction peaks up to 208 K. Furthermore, a thermal expansion study was performed with this technique from 100 to 383 K (near of its melting point) adressing questions about the nature and consequences of the ion self-assembly of this (µ-oxido)-bridged binuclear iron(III) complex, as well as the molecular motion of the imidazolium cation within the crystalline structure as a response to the temperature effect. Finally, we present a deep magnetic study based on magnetic susceptibility, magnetization and Mössbauer measurements, where the strong antiferromagnetic exchange coupling detected is due to the occurrence of a µ-oxido bridge between the Fe(III), giving rise to an intra-dimeric antiferromagnetic exchange coupling of -308 cm-1.Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 funded by SODERCAN_FEDER) , Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239-C2-(1,2)-P)

Cubane-type Mo3FeS44+,5+ complexes containing outer diphosphane ligands: ligand substitution reactions, spectroscopic studies, and electronic structure

A general protocol to access Mo3FeS44+ clusters selectively modified at the Fe coordination site is presented starting from the all-chlorine Mo3(FeCl)S4(dmpe)3Cl3 (1) [dmpe = 1,2-bis(dimethylphosphane-ethane)] cluster and tetrabutylammonium salts (n-Bu4NX) (X = CN–, N3–, and PhS–). Clusters Mo3(FeX)S4(dmpe)3Cl3 [X = CN– (2), N3– (3), and PhS– (4)] are prepared in high yield, and comparison of geometric and redox features upon modification of the coordination environment at the Fe site at parity of ligands at the Mo sites is also presented. The existence of the cubane-type Mo3FeS44+,5+ redox couple is demonstrated by cyclic voltammetry and for compound 1 by cluster synthesis and X-ray structure determinations. Ground states for the 1/1+ redox couple are evaluated on the basis of magnetic susceptibility measurements, electron paramagnetic resonance, and 57Fe Mössbauer spectroscopy aimed at providing an input of experimental data for electronic structure determination based on density functional theory calculations

Cubane-Type Mo₃FeS₄^4+,5+ Complexes Containing Outer Diphosphane Ligands: Ligand Substitution Reactions, Spectroscopic Studies, and Electronic Structure

A general protocol to access Mo₃FeS₄⁴⁺ clusters selectively modified at the Fe coordination site is presented starting from the all-chlorine Mo₃(FeCl)­S₄(dmpe)₃Cl₃ (<b>1</b>) [dmpe = 1,2-bis­(dimethylphosphane-ethane)] cluster and tetrabutylammonium salts (<i>n</i>-Bu₄NX) (X = CN^–, N₃^–, and PhS^–). Clusters Mo₃(FeX)­S₄(dmpe)₃Cl₃ [X = CN^– (<b>2</b>), N₃^– (<b>3</b>), and PhS^– (<b>4</b>)] are prepared in high yield, and comparison of geometric and redox features upon modification of the coordination environment at the Fe site at parity of ligands at the Mo sites is also presented. The existence of the cubane-type Mo₃FeS₄^4+,5+ redox couple is demonstrated by cyclic voltammetry and for compound <b>1</b> by cluster synthesis and X-ray structure determinations. Ground states for the <b>1</b>/<b>1</b>⁺ redox couple are evaluated on the basis of magnetic susceptibility measurements, electron paramagnetic resonance, and ⁵⁷Fe Mössbauer spectroscopy aimed at providing an input of experimental data for electronic structure determination based on density functional theory calculations

Cubane-Type Mo₃FeS₄^4+,5+ Complexes Containing Outer Diphosphane Ligands: Ligand Substitution Reactions, Spectroscopic Studies, and Electronic Structure

A general protocol to access Mo₃FeS₄⁴⁺ clusters selectively modified at the Fe coordination site is presented starting from the all-chlorine Mo₃(FeCl)­S₄(dmpe)₃Cl₃ (<b>1</b>) [dmpe = 1,2-bis­(dimethylphosphane-ethane)] cluster and tetrabutylammonium salts (<i>n</i>-Bu₄NX) (X = CN^–, N₃^–, and PhS^–). Clusters Mo₃(FeX)­S₄(dmpe)₃Cl₃ [X = CN^– (<b>2</b>), N₃^– (<b>3</b>), and PhS^– (<b>4</b>)] are prepared in high yield, and comparison of geometric and redox features upon modification of the coordination environment at the Fe site at parity of ligands at the Mo sites is also presented. The existence of the cubane-type Mo₃FeS₄^4+,5+ redox couple is demonstrated by cyclic voltammetry and for compound <b>1</b> by cluster synthesis and X-ray structure determinations. Ground states for the <b>1</b>/<b>1</b>⁺ redox couple are evaluated on the basis of magnetic susceptibility measurements, electron paramagnetic resonance, and ⁵⁷Fe Mössbauer spectroscopy aimed at providing an input of experimental data for electronic structure determination based on density functional theory calculations

Exploiting redox activity of MIL-100(Fe) carrier enables carvacrol prolonged antimicrobial activity

The design of efficient food contact materials that maintain optimal levels of food safety is of paramount relevance to reduce the increasing foodborne illnesses. In this work, we develop a smart composite MOF-based material that fosters a unique prolonged antibacterial activity. The composite is obtained by entrapping a natural preserving food molecule, carvacrol, into the mesoporous MIL-100(Fe) material following a direct and biocompatible impregnation method and obtaining particularly high payloads. By exploiting the intrinsic redox nature of MIL-100(Fe) material it is possible to achieve a prolonged activity against E. coli bacteria due to a triggered two-step carvacrol release of films containing the carvacrol@MOF composite. Essentially, it was discovered that based on the underlying chemical interaction among MIL-100(Fe) and carvacrol, it is possible to undergo a reversible charge transfer process between the metallic MOF counterpart and the carvacrol upon certain physical stimuli. During this process, the preferred carvacrol binding site has been monitored by IR, Mössbauer and EPR spectroscopies and is supported by theoretical calculations

Synthesis and Structural/Physical Properties of U3Fe2Ge7: A Single-Crystal Study

International audienceA single crystal of U3Fe2Ge7 was synthesized by the tin-flux method, and its structural and electronic properties were studied. The compound crystallizes in the orthorhombic crystal structure of La3Co2Sn7 type with two Wyckoff sites for the U atoms. U3Fe2Ge7 displays a ferromagnetic order below TC = 62 K. Magnetization measurements in static (up to 14 T) and pulsed (up to 60 T) magnetic fields revealed a strong two-ion uniaxial magnetic anisotropy. The easy magnetization direction is along the c axis and the spontaneous magnetic moment is 3.3 μB per formula unit at 2 K. The moment per Fe atom is 0.2 μB, as follows from Mossbauer spectroscopy. The magnetic moments are oriented perpendicular to the shortest inter-uranium distances that occur within the zigzag chains in the ab plane, contrary to other U-based isostructural compounds. The magnetization along the a axis reveals a first-order magnetization process that allows for a quantitative description of the magnetic anisotropy in spite of its enormous energetic strength. The strong anisotropy is reflected in the specific heat and electrical resistivity that are affected by a gap in magnon spectrum

Rare Earth Element Phyto-Availability in Abandoned Mining Areas

International audienceRare Earth Elements (REE) are emergent anthropogenic contaminants. Currently, there are knowledge gaps in assessing the environmental risks posed by these contaminants. High demand for modern technology has led to increased REE use, resulting in elevated REE concentrations in the environment. Therefore, demonstrating a need to understand the behavior, fate, and cycling of REEs as emergent pollutants.The physical and chemical speciation of REE is (i) reflective of their origin and the encountered processes within the environment and (ii) potentially influences their availability and toxicity. To date, very few publications have focused on how the physical and chemical speciation of REE controls phyto-availability. Thus, an evaluation of the spontaneous vegetation at three abandoned mining sites in Portugal was carried out in November 2020 (Figure 1). Spontaneous vegetation and related media (soils and surface waters) were collected from inside and outside of mining areas with the intention of analyzing REE dynamics in rhizosphere soils and subsequent REE dissemination in plants. Trace element concentrations were analyzed in soil and plant samples using inductively coupled plasma mass spectroscopy (ICP-MS). Measurements of key parameters (pH, Eh, and major anions) and determination of dissolved organic carbon and trace element concentrations were performed in water samples by multi-meter, ion chromatography, total carbon-analyzer, and ICP-MS, respectively. Measurements were then used to decipher how the chemical compositions of waters and soils can be linked to that of plants and, more precisely, to the fate of REE in planted environments. Contrasting REE concentrations and patterns were observed in water samples regarding the prevailing environmental conditions.In addition, the complex biogeochemical interactions in rhizospheres potentially alter the speciation and phyto-availability of REE. Therefore, rhizosphere soil samples were paired with bulk soil samples to elucidate the impact of plant and microorganism bioweathering processes on REE speciation.Ultimately, this field study aims to evaluate the environmental risk posed by anthropogenic REE contamination and contribute to a body of knowledge on the circular economy of REE. Further study of plant REE uptake mechanisms and toxicological responses to REE contamination is planned for future laboratory experiments

Смешанная проводимость и мёссбауэровские спектры (La0.5Sr0.5)1 — xFe1 — yAlyO3 — d (x = 0 — 0.05, y = 0 — 0.30)

Aluminum incorporation in the rhombohedrally distorted perovskite lattice of (Lao.sSro.sJi-.xFe^AlyCb^ (x = 0 -0 .0 5 , у = 0-0.30) decreases the unit cell volume and partial ionic and p-type electronic conductivities, while the oxygen nonstoichiometry and thermal expansion at 900-1200 К increase on doping. The creation o f А-site cation vacancies has an opposite effect on the transport properties of Al-substituted ceramics. The maximum А-site deficiency tolerated by the (La,Sr)(Fe,Al)03_￡ structure is however limited, close to 3-4%. The Mossbauer spectroscopy revealed progressive localization o f electron holes and a mixed charge-compensation mechanism, which results in higher average oxidation state of iron when Al3+ concentration increases. The average thermal expansion coefficients of (La0.5Sr0.5) i - ,F e 1_>AlJ,O3 _a are (12.2-13.0) x lO ^K " 1 at 300-900K and (20.1-30.0) x 10"6K_I at 900-1200K in air. The steady-state oxygen permeability (OP) of dense Al-containing membranes is determined mainly by the bulk ionic conductivity. The ion transference numbers at 973-1223 К in air, calculated from the oxygen permeation and faradaic efficiency (FE) data, vary in the range 1 x 10_4-3 x 10-3, increasing with temperature. © 2006 Elsevier Inc. All rights reserved

Conducting Anilate-Based Mixed-Valence Fe(II)Fe(III) Coordination Polymer: Small-Polaron Hopping Model for Oxalate-Type Fe(II)Fe(III) 2D Networks

The mixed-valence FeIIFeIII 2D coordination polymer formulated as [TAG][FeIIFeIII(ClCNAn)3]·(solvate) 1 (TAG = tris(amino)-guanidinium, ClCNAn2− = chlorocyanoanilate dianionic ligand) crystallized in the polar trigonal space group P3. In the solid-state structure, determined both at 150 and at 10 K, anionic 2D honeycomb layers [FeIIFeIII(ClCNAn)3]− establish in the ab plane, with an intralayer metal−metal distance of 7.860 Å, alternating with cationic layers of TAG. The similar Fe−O distances suggest electron delocalization and an average oxidation state of +2.5 for each Fe center. The cation imposes its C3 symmetry to the structure and engages in intermolecular N−H···Cl hydrogen bonding with the ligand. Magnetic susceptibility characterization indicates magnetic ordering below 4 K and the presence of a hysteresis loop at 2 K with a coercive field of 60 Oe. Mössbauer measurements are in agreement with the existence of Fe(+2.5) ions at RT and statistic charge localization at 10 K. The compound shows semiconducting behavior with the in-plane conductivity of 2 × 10−3 S/cm, 3 orders of magnitude higher than the perpendicular one. A small-polaron hopping model has been applied to a series of oxalate-type FeIIFeIII 2D coordination polymers, providing a clear explanation on the much higher conductivity of the anilate-based systems than the oxalate ones.The work in France was supported by the CNRS, the University of Angers, the Erasmus program (mobility grant to N.M.), the RFI Regional project LUMOMAT (grant to A.A., project ASCO MMM), and the PIA project “Lorraine Université d'Excellence” (reference ANR-15-IDEX-04-LUE). This work was supported in Italy by the Fondazione di Sardegna-Convenzione triennale tra la Fondazione di Sardegna e gli Atenei Sardi, Regione Sardegna-L.R. 7/2007 annualità 2016-DGR 28/21 del 17.05.2015 “Innovative Molecular Functional Materials for Environmental and Biomedical Applications” and INSTM. Work in Spain was supported by the Spanish Ministerio de Economi ́ a y Competitividad (Grants FIS2012-37549-C05-05, FIS2015-64886-C5-4-P, CTQ2015- 64579-C3-3-P, and CTQ2015-71287-R) and Generalitat de Catalunya (2014SGR301, 2017SGR797, and XRQTC and the CERCA program). E.C. acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2015-0496. J.C.W. and B.J.C.V. acknowledge Fundaca̧ o para a Cie ̃ ncia e a Tecnologia (FCT, ̂ Portugal) through the project UID/Multi/04349/2013.Peer reviewe