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A detailed investigation on the coordination environment of the Co2+ ion has been carried out with the intent of quantifying the contact ion-pair formation in dilute (0.1 mol L−1) CoCl2 aqueous, methanol (MeOH), and ethanol (EtOH) solutions. An effective approach has been employed combining UV-vis measurements, X-ray absorption spectroscopy, and density functional theory (DFT). The CoCl2 metal salt is fully dissociated in aqueous solution with the Co2+ cation first hydration shell formed by six water molecules arranged in an octahedral fashion. On the other hand, the chloride anion enters the Co2+ coordination sphere giving rise to ionic pairs in MeOH and EtOH solution due to the weaker solvation ability of these solvents. The Co–Cl distances are 2.34(2) and 2.26(3) Å in MeOH and EtOH solutions, respectively, as determined by extended X-ray absorption fine structure data analysis. In MeOH solution the dominant species is the octahedral [CoCl(MeOH)5]+ complex, while for EtOH the spectral evidence can be interpreted with an equilibrium between different four-fold metal-chloro species. Structural distortions in the coordination clusters have been evidenced by the X-ray absorption near-edge structure analysis aided by DFT optimizations and allowed us to rationalize the spectroscopic outcome of the UV-vis measurements. The adopted combined approach provided an all-around structural picture of the coordination complexes formed when the CoCl2 salt is dissolved in solvents with different coordinating properties. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) including oxalatoborate anions, like bis(oxalato)borate (BOB) and difluoro(oxalato)borate (DFOB) are extensively used in the battery sector as additives to promote the formation of protective layers on the surface of high-voltage cathode materials. In this work four ILs have been synthesized: N-ethoxyethyl-N-methyl piperidinium bis(oxalato)borate (PIP1,2O2BOB), N-ethoxyethyl-N-methylpiperidinium difluoro(oxalato)borate (PIP1,2O2 DFOB), N-propyl-N-methylpiperidinium bis(oxalato)borate (PIP1,3BOB) and N-propyl-N-methylpiperidinium difluo ro(oxalato)borate (PIP1,3DFOB) and their thermal properties have been linked to their structure. The presence of an oxygen atom in the PIP1,2O2 lateral chain suppresses crystallization of the ILs. Furthermore, PIP1,2O2DFOB shows a lower glass transition temperature than PIP1,2O2BOB. These observations have been explained using a combined molecular dynamics and density functional theory approach and an increase in the degree of freedom of the lateral chain of the cation due to the ether oxygen has been found. Comparing PIP1,2O2DFOB and PIP1,2O2BOB, a notable interaction between different domains of the anions is observed and is stronger in the DFOB case due to the charge-delocalization induced by the fluorine atoms, which generates a relatively positive charge on the boron atom. This is correlated to the weaker cation--anion attraction which hinders the glass transition of PIP1,2O2DFOB. [ABSTRACT FROM AUTHOR]

We have carried out a comparative study on three sets of eutectic mixtures based on choline chloride (ChCl) and hydroxyphenol isomers having two hydroxyl groups in the ortho-, meta-, and para-positions of the aromatic ring, namely catechol (Cate), resorcinol (Reso), and hydroquinone (Hydro), respectively. Differential scanning calorimetry highlighted a different thermal behavior of the mixtures depending on the composition and precursor isomerism. These systems behave as deep eutectic solvents (DESs) with the exception of the ChCl/Cate mixture at a 1 : 0.75 molar ratio, the ChCl/Reso mixtures at 1 : 2 and 1 : 3 molar ratios, and the ChCl/Hydro mixture at a 1 : 3 molar ratio. Infrared spectroscopy measurements and molecular dynamics simulations show that the stronger hydrogen-bonding (H-bonding) in the mixed states compared to the pure precursors is key for the formation of a DES. This interaction is mostly reliant on interconnected chloride anion coordination shells thanks to the two hydroxyl groups of the hydroxyphenol molecules, which can bridge between different anions to form an extended H-bond network. This structural arrangement maximizes the interactions and is enhanced by the 1 : 0.75 and 1 : 1 molar ratios, while increasing the hydroxyphenol concentration translates into a lowering of the total number of H-bonds formed in the mixture. This is the basis for the different thermal behavior and points to nearly equimolar compositions between the components, as ideally suited to achieve a DES from these precursors. The obtained insights are able to explain the structure–property relationships for the studied systems and are deemed useful for more conscious development of these inherently tuneable solvents. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the electrochemical intercalation of Ca2+ ions within the lattice of anatase nanotubes (a‐NTs) synthesized by hydrothermal treatment of TiO2/NaOH precursors followed by Na+/H+ ion exchange and H2O‐loss at high temperature in air. Scanning electron microscopy, X‐ray diffraction, and Raman spectroscopy confirm the formation of nanosized anatase, whereas transmission electron microscopy highlights the formation of nanotubular morphologies with an average diameter of 10 nm. TiO2 electrodes are able to deliver reversible specific capacities in aprotic batteries vs. calcium metal or in hybrid configurations vs. capacitive activated carbon using aprotic electrolytes (i. e., Ca(BH4)2 in tetrahydrofuran or Ca(TFSI)2 in dimethoxyethane, respectively). The electrochemical intercalation of Ca2+ ions into the anatase lattice is confirmed by X‐ray absorption spectroscopy in close comparison with Na+ and Li+ intercalations. Ca2+ incorporation leads to the partial amorphization of the TiO2 lattice despite the limited Ca/Ti ratio (i. e., 0.09) obtained in discharge. The analysis of the extended X‐ray absorption fine structure region allows the determination of the local structure of the incorporated Ca2+ ions and confirms that a disordered environment is obtained after the electrochemical reaction. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy (XAS) has been employed to carry out structural characterization of the local environment around mercury after the dissolution of the HgCl2 molecule. A combined EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) data analysis has been performed on the Hg L3-edge absorption spectra recorded on 0.1 M HgCl2 solutions in water, methanol (MeOH), acetone and acetonitrile. The Hg–Cl distance determined by EXAFS (2.29(2)–2.31(2) Å) is always comparable to that found in the HgCl2 crystal (2.31(2) Å), demonstrating that the HgCl2 molecule dissolves in these solvents without dissociating. A small sensitivity of EXAFS to the solvent molecules interacting with HgCl2 has been detected and indicates a high degree of configurational disorder associated with this contribution. XANES data analysis, which is less affected by the disorder, was therefore carried out for the first time on these systems to shed light into the still elusive structural arrangement of the solvent molecules around HgCl2. The obtained results show that, in aqueous and MeOH solutions, the XANES data are compatible with three solvent molecules arranged around the HgCl2 unit to form a trigonal bipyramidal structure. The determination of the three-body Cl–Hg–Cl distribution shows a certain degree of uncertainty around the average 180° bond angle value, suggesting that the HgCl2 molecule probably vibrates in the solution around a linear configuration. [ABSTRACT FROM AUTHOR]

The satisfactory rationalization of complex reactive pathways in solution chemistry may greatly benefit from the combined use of advanced experimental and theoretical complementary methods of analysis. In this work, we combine X‐Ray Absorption and 1H NMR spectroscopies with state‐of‐the‐art Multivariate Curve Resolution and theoretical analyses to gain a comprehensive view on a prototypical reaction involving the variation of the oxidation state and local structure environment of a selected metal ion coordinated by organic ligands. Specifically, we investigate the 2‐cyano‐2‐phenylpropanoic acid reduction of the octahedral complex established by the Cu2+ ion with terpyridine to the tetrahedral complex formed by Cu+ and neocuproine. Through our interdisciplinary approach we gain insights into the nature, concentration time evolution and structures of the key metal (XAS measurements) and organic (1H NMR measurements) species under reaction. We believe our method may prove to be useful in the toolbox necessary to understand the mechanisms of reactive processes of interest in solution. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations and X-ray absorption spectroscopy (XAS) were employed to study the solvation of Zn2+ ion in dry [Cnmim][Tf2N] (n = 2, 4; 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) room temperature ionic liquids (RTILs). For [C4mim][Tf2N] also a water-saturated system was considered. The thermodynamic parameters of single ion solvation and transfer from water to the RTIL, as well as the structural information, were calculated by means of MD simulations and our study evidences that both structural and thermodynamic features can be reproduced by MD in good agreement with the experimental data. In the case of [C4mim][Tf2N], enthalpies and entropies of solvation and transfer from water to the RTIL were also obtained. The Zn2+ ion results more favorably solvated in water than in the RTIL and this seems to be caused by the more negative entropy of solvation in the latter liquid. This can be explained by the higher ordering imposed by the metal ion when solvated in [C4mim][Tf2N] with respect to water. When the transfer of Zn2+ in a water/[C4mim][Tf2N] biphasic system is considered, the results show a positive value for the free energy of transfer and the metal ion always prefers to remain solvated in water than in the water-saturated RTIL phase. This theoretical result was confirmed by the analysis of XANES (X-ray absorption near edge structure) and the EXAFS (extended X-ray absorption fine structure) spectra of Zn(Tf2N)2 solutions in [C4mim][Tf2N] in the presence of water. [ABSTRACT FROM AUTHOR]

Manganese excess can induce in humans a neurological disorder known as manganism. A possible remedy should be chelation therapy, even though a chelation schedule for manganism has not been currently established. para-Aminosalicylic acid (PAS) has demonstrated effectiveness in reducing manganism symptoms. In this work, a study of the protonation equilibria of para-aminosalicylic acid and of its N-acetylated metabolite (Ac-PAS) and of their complexation reactions with Mn2+ is presented, and also extended to the main essential metal ions Cu2+ and Fe3+. A number of complementary techniques (potentiometry, spectrophotometry, fluorimetry, EPR) have been used for a thorough comprehension of the protonation and complex formation equilibria, with the addition of DFT calculations, which provide insights into the relative stabilities and electronic properties of the formed species. Both PAS and Ac-PAS form 1 : 1 and 1 : 2 metal : ligand complexes with the target Mn2+ ion; surprisingly the N-acetylated metabolite forms stronger complexes, whose implications in chelation therapy have been pointed out by a speciation study. It is presumed that the relatively small metabolite can penetrate across the blood-brain-barrier and exert its Mn-mobilizing action intracellularly in vulnerable neurons. [ABSTRACT FROM AUTHOR]