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A thorough structural study of La(NO 3) 3 salt solutions in mixtures of the ethylammonium nitrate (EAN) ionic liquid (IL) and water with EAN molar fraction (χ E A N) ranging from 0 to 1 has been carried out by means of X-ray absorption spectroscopy (XAS) measurements at the La K-edge and molecular dynamics (MD) simulations. Both the XAS and MD outcomes agree in finding that the composition of the La3+ ion first solvation shell undergoes steadily changes when moving from pure water to pure EAN. Upon increasing of the IL concentration, the La3+ solvation complexes progressively lose water molecules to accommodate more and more nitrate anions, and the ratio between the two ligands continuously changes across the explored composition range. The nitrate ligands coordinate the metal ion only in a monodentate fashion for the lower EAN contents, while the percentage of bidentate nitrates becomes more and more predominant as the EAN concentration increases. When moving from pure water to pure EAN, the La3+ ion coordination passes from a 9-fold tricapped trigonal prismatic geometry to a 12-fold icosahedral one, while a 10-fold coordination with bicapped square antiprism geometry is the dominant species for the mixed compositions. The remarkable flexibility of this solvation complex in accommodating a variable amount of water molecules and nitrate ligands at dependence of the system composition is key for its predominance in all the EAN/water mixtures. • The solvation properties of the La(NO 3) 3 salt in aqueous mixtures of ethylammonium nitrate (EAN) were studied. • The speciation of the La3+ complexes undergoes steady changes from pure water to pure EAN. • Nitrate anions enter the La3+ first solvation sphere upon increasing EAN concentration. • The nitrate ligands are monodentate for low EAN contents, while bidentate coordination occurs for higher EAN concentrations. • In the EAN/water mixtures the dominant species is a highly flexible 10-fold complex with bicapped square antiprism geometry. [ABSTRACT FROM AUTHOR]

The solvation of the Ag+ ion in the 1-butyl-3-methylimidazolium tetrafluoroborate ([C 4 mim][BF 4 ]) ionic liquid (IL) has been studied by means of experimental and theoretical methods with the aim of elucidating the cation coordination structure and thermodynamic properties. Car-Parrinello molecular dynamics (CPMD) simulations showed that the Ag+ ion is coordinated by an average number of four [BF 4 ]− anions in a pseudo-tetrahedral geometry. A high configurational disorder of the first solvation sphere is found, where the anions can be found both in mono- and bidentate coordination mode around the Ag+ ion. Also, a solvational equilibrium is observed as due to [BF 4 ]− anion dissociation along the trajectory. The analysis of X-ray absorption spectroscopy data confirmed the picture provided by the CPMD simulation. Classical molecular dynamics simulations were carried out to obtain the single-ion solvation thermodynamic parameters. The negative water → IL free energy of transfer suggests that the Ag+ ion is more favorably solvated in the [C 4 mim][BF 4 ] IL than in water. This behavior is due to a balance between the enthalpic and entropic contributions, which allows to find a rationale to the strong solvation capabilities of BF 4 -based ILs towards Ag+. • The coordination environment and solvation thermodynamics of the Ag+ ion the [C 4 mim][BF 4 ] ionic liquid are analyzed. • CPMD simulations show that the Ag+ ion is coordinated by four [BF 4 ]− anions in a tetrahedral geometry. • XAS data confirm the local structure around the Ag+ ion and a high configurational disorder of the solvation sphere. • Ag+ ion is more favorably solvated in [C 4 mim][BF 4 ] than in water. [ABSTRACT FROM AUTHOR]

Transition metal chemistry in solution is central to key processes in biology and catalysis. Achieving accurate knowledge on the structural and electronic properties of the relevant reaction intermediates requires the use of innovative and complementary spectroscopic probes. Herein, we combine X-ray Absorption Spectroscopy (XAS) and 1 H-NMR to investigate the exchange reaction between two prototypical Cu coordination complexes in solution. By means of multivariate and theoretical analyses, we identify the number, nature and concentration time evolution of the relevant reaction intermediates and quantitatively determine their structures. The XAS and NMR techniques are proven to be complementary experimental tools to track the fate of both the metal and organic portions of reactive systems involving transition metals. The employed combined experimental and theoretical method may be useful in the study of reactive systems involving intermediates that may be labile or silent to conventional detection. • A combined XAS/NMR analysis has been used to investigate a reaction in solution. • Multivariate and theoretical analyses have provided mechanistic information. • The approach is promising to study the reactivity of transition metal complexes. [ABSTRACT FROM AUTHOR]