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Extended x-ray absorption fine structure (EXAFS) spectroscopy has been used to investigate the species and structures existing in a series of ZnCl2-H2O-NaCl solutions with different chloride/zinc ratios and in a solution of ZnCl2 in the protic ionic liquid ethyl ammonium nitrate (EAN). The average coordination numbers and distances of zinc species were determined from the analysis of the EXAFS data. In aqueous solution the number of chloride ions tightly bounded to Zn2+ is significantly related to the chloride/zinc ratio, and no inner complex formation between Zn2+ and Cl- ions has been detected for low ZnCl2 concentration (0.1 and 0.2 M). Conversely, in the same concentration range (0.13 M) the ZnCl2 species do not dissociate in EAN and the Zn2+ first coordination shell has two chloride ions and is completed by two oxygen atoms of the nitrate anion. The results of this investigation show that notwithstanding the existence of similar characteristics between EAN and water, the solvation properties of the two solvents are markedly different. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy (XAS) has been used to unveil the bromide ion local coordination structure in 1-alkyl-3-methylimidazolium bromide [Cnmim]Br ionic liquids (ILs) with different alkyl chains. The XAS spectrum of 1-ethyl-3-methylimidazolium bromide has been found to be different from those of the other members of the series, from the butyl to the decyl derivatives, that have all identical XAS spectra. This result indicates that starting from 1-buthyl-3-methylimidazolium bromide the local molecular arrangement around the bromide anion is the same independently from the length of the alkyl chain, and that the imidazolium head groups in the liquid ILs with long alkyl chains assume locally the same orientation as in the [C4mim]Br crystal. With this study we show that the XAS technique is an effective direct tool for unveiling the local structural arrangements around selected atoms in ILs. [ABSTRACT FROM AUTHOR]

Highlights: [•] XANES spectra of Ionic Liquids have been collected and analysed. [•] Small local structural changes are detectable by XANES. [•] A quantitative analysis of XANES is possible also for halide ions. [ABSTRACT FROM AUTHOR]

Thestructural and dynamic properties of 1-butyl-3-methylimidazoliumbromide ([C4mim]Br)/water mixtures with different molarratios have been investigated using classical molecular dynamics (MD)simulations, and the reliability of the results has been assessedby comparison with extended X-ray absorption fine structure experimentaldata. The analysis of the MD trajectories has highlighted the presenceof a complex network of interactions among cations, anions, and watermolecules, even if water molecules have been found to interact preferentiallywith the Br–anion. The existence of solvent-sharedion pairs has been detected in all of the investigated mixtures withone or more water molecules acting as a bridge between the cationand the anion, also when water is present in great excess ([C4mim]Br/water ratio of 1:200). The dynamic behavior of thesystems has been characterized starting from the MD trajectories.Water molecules have been found to quicken the dynamics of the ILcations and anions, and acceleration involves all of the investigatedmotions. [ABSTRACT FROM AUTHOR]

ExtendedX-ray absorption fine structure (EXAFS) spectroscopy isemployed, in conjunction with molecular dynamics (MD) simulations,to investigate the interaction of water with the Br–ion in an imidazolium-based ionic liquid (IL). 1-Butyl-3-methylimidazoliumbromide/water mixtures with molar ratios ranging from 1:3 to 1:200have been analyzed, and a clear picture of the structural arrangementsof the water molecules inside the IL has been obtained from the synergicinterpretation of the EXAFS and MD data. At the lowest investigatedwater content, the presence of water is mainly detected around theBr–anion. Upon increasing the water fraction, morewater molecules enter the Br–first-coordinationshell but always in a lower number than what is needed to saturatethe inner sphere. This suggests that interactions also exist betweenwater and the imidazolium cation. The existence of tight ion pairshas been evidenced, even when water is present in the mixtures ingreat excess. [ABSTRACT FROM AUTHOR]