On the Coordination Chemistry of the lanthanum(III) Nitrate Salt in EAN/MeOH Mixtures

Migliorati, Valentina; Gibiino, Alice; Lapi, Andrea; Busato, Matteo; D’Angelo, P.

doi:10.1021/acs.inorgchem.1c01375

Cited by 12 publications

(10 citation statements)

References 75 publications

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“…In particular, the methanol solution FT spectrum shows the presence of a peak at about 3.6 Å associated with a second shell contribution, which is not observed in the water FT data (Figure B). It is noteworthy that, in previous investigations on the solvation properties of La(NO 3 ) 3 and Ce(NO 3 ) 3 in ethylammonium nitrate, this peak was found to be due to MS effects associated with the coordinating nitrate ligands. , The whole picture therefore provides a first experimental confirmation that the nitrate anion is able to enter the La 3+ ion coordination sphere in methanol solution, at variance with the aqueous one, in agreement with the MD results. Note that other contributions to the FT second-shell peak may arise from the La–C MeOH and La–N NO 3 – paths, which are in any case absent in water.…”

Section: Resultssupporting

confidence: 87%

Direct Observation of Contact Ion-Pair Formation in La³⁺ Methanol Solution

et al. 2022

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An approach combining molecular dynamics (MD) simulations and X-ray absorption spectroscopy (XAS) has been used to carry out a comparative study about the solvation properties of dilute La(NO 3 ) 3 solutions in water and methanol, with the aim of elucidating the still elusive coordination of the La 3+ ion in the latter medium. The comparison between these two systems enlightened a different behavior of the nitrate counterions in the two environments: while in water the La(NO 3 ) 3 salt is fully dissociated and the La 3+ ion is coordinated by water molecules only, the nitrate anions are able to enter the metal first solvation shell to form inner-sphere complexes in methanol solution. The speciation of the formed complexes showed that the 10-fold coordination is preferential in methanol solution, where the nitrate anions coordinate the La 3+ cations in a monodentate fashion and the methanol molecules complete the solvation shell to form an overall bicapped square antiprism geometry. This is at variance with the aqueous solution where a more balanced situation is observed between the 9-and 10-fold coordination. An experimental confirmation of the MD results was obtained by La K-edge XAS measurements carried out on 0.1 M La(NO 3 ) 3 solutions in the two solvents, showing the distinct presence of the nitrate counterions in the La 3+ ion first solvation sphere of the methanol solution. The analysis of the extended X-ray absorption fine structure (EXAFS) part of the absorption spectrum collected on the methanol solution was carried out starting from the MD results and confirmed the structural arrangement observed by the simulations.

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Section: Resultssupporting

confidence: 87%

Direct Observation of Contact Ion-Pair Formation in La³⁺ Methanol Solution

et al. 2022

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“…When dealing with metal ion solutions, XAS is the technique of choice to obtain an accurate determination of the local structure around the photoabsorbing center. − ,, XAS spectra have been collected on the NiCl 2 ·6H 2 O:urea 1:3.5 MDES and on the NiCl 2 ·6H 2 O:urea:water 1:3.5:26 mixture, and they are shown in Figure . Here, the data are compared to the XAS spectrum collected on a 0.2 M Ni(NO 3 ) 2 aqueous solution as the reference system.…”

Section: Resultsmentioning

confidence: 99%

“…The charges of the ionic species were scaled by a factor of 0.9, as this strategy was previously demonstrated to improve the transport properties and to take into account polarization effects implicitly. − A cutoff radius of 12 Å was employed for all the non-bonded interactions, while the long-range electrostatic forces were computed with the particle mesh Ewald method. , All the stretching vibrations involving the hydrogen atoms were constrained with the LINCS algorithm . The employed simulation protocol is reported elsewhere, ,− though details are provided in the SI.…”

Section: Methodsmentioning

confidence: 99%

On the Role of Water in the Formation of a Deep Eutectic Solvent Based on NiCl₂·6H₂O and Urea

et al. 2022

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The metal-based deep eutectic solvent (MDES) formed by NiCl 2 ·6H 2 O and urea in 1:3.5 molar ratio has been prepared for the first time and characterized from a structural point of view. Particular accent has been put on the role of water in the MDES formation, since the eutectic could not be obtained with the anhydrous form of the metal salt. To this end, mixtures at different water/MDES molar ratios ( W ) have been studied with a combined approach exploiting molecular dynamics and ab initio simulations, UV–vis and near-infra-red spectroscopies, small- and wide-angle X-ray scattering, and X-ray absorption spectroscopy measurements. In the pure MDES, a close packing of Ni 2+ ion clusters forming oligomeric agglomerates is present thanks to the mediation of bridging chloride anions and water molecules. Conversely, urea poorly coordinates the metal ion and is mostly found in the interstitial regions among the Ni 2+ ion oligomers. This nanostructure is disrupted upon the introduction of additional water, which enlarges the Ni–Ni distances and dilutes the system up to an aqueous solution of the MDES constituents. In the NiCl 2 ·6H 2 O 1:3.5 MDES, the Ni 2+ ion is coordinated on average by one chloride anion and five water molecules, while water easily saturates the metal solvation sphere to provide a hexa-aquo coordination for increasing W values. This multidisciplinary study allowed us to reconstruct the structural arrangement of the MDES and its aqueous mixtures on both short- and intermediate-scale levels, clarifying the fundamental role of water in the eutectic formation and challenging the definition at the base of these complex systems.

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“…Initial configurations were built by randomizing the atomic positions with the PACKMOL package, then each system was equilibrated under NVT conditions following a heating ramp up to 500 K, staying at high temperature for 2 ns, and gradually cooling down to 308 K. High-temperature equilibrations were previously observed to be recommendable for viscous systems like DESs and ionic liquids. ,− The final production runs for data collection were performed under NVT conditions at 308 K for 50 ns, being this temperature just above the determined MPs of the two eutectics ( vide infra ). The temperature was controlled by coupling the systems to a Nose–Hoover thermostat with a relaxation constant of 0.5 ps, while the equations of motion were integrated by means of the leap-frog algorithm with a 1 fs time step and coordinates were saved every 100 steps.…”

Section: Methodsmentioning

confidence: 99%

Structural Study of a Eutectic Solvent Reveals Hydrophobic Segregation and Lack of Hydrogen Bonding between the Components

Busato

Mannucci

Lisio

et al. 2022

ACS Sustainable Chem. Eng.

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An in-depth study of the hydrophobic eutectic solvent formed by butylated hydroxytoluene (BHT) and L-menthol (MEN) in a 1:3 molar ratio has been carried out using an integrated approach that combines differential scanning calorimetry (DSC), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, small-and wide-angle X-ray scattering (SWAXS), and molecular dynamics (MD) simulations. The obtained data have been step-by-step compared to those collected on the eutectic formed by 3,5-di-tert-butyltoluene (TBT) and MEN in the same molar ratio, where TBT is analogous to the BHT without the hydroxyl group. The DSC characterization showed comparable results between the two systems, evidencing that the hydroxyl group of the BHT has little or no impact on the thermal behavior of the BHT:MEN eutectic. Both the FTIR and MD results agree in finding that no hydrogen bond (H-bond) interactions are played by the BHT because of the high steric hindrance suffered by its hydroxyl group so that the only established H-bonds are those between MEN molecules. The incompatibility between the components in terms of H-bonds formation results in hydrophobic segregation promoting the MEN−MEN interactions, which are even more intense than in the pure compound. The threedimensional arrangement between the components showed a remarkable degree of structural order among the alkyl functional groups, suggesting that the apolar−apolar attraction might be the driving force of the eutectic formation. This picture is translated into the establishment of an intermediate-range organization in solution, as evidenced by the SWAXS data. The overall impact of this study is that of pushing a little bit further the definition of these eutectics, indicated until now as extensively H-bonded systems.

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On the Coordination Chemistry of the lanthanum(III) Nitrate Salt in EAN/MeOH Mixtures

Cited by 12 publications

References 75 publications

Direct Observation of Contact Ion-Pair Formation in La³⁺ Methanol Solution

Direct Observation of Contact Ion-Pair Formation in La³⁺ Methanol Solution

On the Role of Water in the Formation of a Deep Eutectic Solvent Based on NiCl₂·6H₂O and Urea

Structural Study of a Eutectic Solvent Reveals Hydrophobic Segregation and Lack of Hydrogen Bonding between the Components

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On the Coordination Chemistry of the lanthanum(III) Nitrate Salt in EAN/MeOH Mixtures

Cited by 12 publications

References 75 publications

Direct Observation of Contact Ion-Pair Formation in La3+ Methanol Solution

Direct Observation of Contact Ion-Pair Formation in La3+ Methanol Solution

On the Role of Water in the Formation of a Deep Eutectic Solvent Based on NiCl2·6H2O and Urea

Structural Study of a Eutectic Solvent Reveals Hydrophobic Segregation and Lack of Hydrogen Bonding between the Components

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Direct Observation of Contact Ion-Pair Formation in La³⁺ Methanol Solution

Direct Observation of Contact Ion-Pair Formation in La³⁺ Methanol Solution

On the Role of Water in the Formation of a Deep Eutectic Solvent Based on NiCl₂·6H₂O and Urea