Solutes ionic liquids, reaction dynamics

With the intensive development of ultrafast spectroscopic methods, reaction dynamics can be investigated at the subpicosecond time scale. Femtosecond spectroscopy of liquids and solutions allows the study of sol-vent-cage effects on elementary charge-transfer processes. Recent work on ultrafast electron-transfer channels in aqueous ionic solutions is presented (electron-atom or electron-ion radical pairs, early geminate recombination, and concerted electron-proton transfer) and discussed in the framework of quantum theories on nonequilibrium electronic states. These advances permit us to understand how the statistical density fluctuations of a molecular solvent can assist or impede elementary electron-transfer processes in liquids and solutions. 

In 2002 we predicted that non-synthetic applications would have a great chance to be among the first technical ionic liquid applications. This assumption has held true as Chapter 9 clearly proves. Non-synthetic applications are particularly attractive due to their often much shorter development times. Usually, the improvement over existing technology is only based on one or very few specific properties of the ionic liquid, whereas, for most synthetic applications a complex mixture of physicochemical properties in dynamic mixtures has to be considered. This point is well illustrated by the fact that all liquid-liquid biphasic catalysis involves both a reaction and an extraction step. Hence, the ionic liquid catalyst solution has to ftilfil at the same time aU of the requirements to work as a superior reaction medium as well as its role as a suitable extraction medium. The result is a significantly more complex set of material requirements which prolongs the specific ionic liquid development and testing times. 

In fact it is hard to measure the intrinsic anodic behavior of LLMOj, cathode materials in standard electrolyte solutions because at too high potentials the anodic reactions of solution species may dominate the potentio-dynamic response. However, ionic liquid solutions based on quaternary ammonium cations, TFSI anion, and LiTFSI salt demonstrate very high anodic stability. The passivation of Al current collector is excellent in these solutions. So, the anodic stability of Al... 

Figure 11. Schematic representation of sequential events of an SNj ionization reaction in a polar liquid. Elementary events involve contact ion pairs (CIP) and solvent-separated ion pairs (SSIP). In ionic aqueous solutions, the influence of different ion-pair configurations on early electron-transfer trajectories can be considered through the investigation of ultrafast electronic dynamics and radical ion-...

Computational chemistry may contribute to understand what happens at the liquid-liquid interface in the assisted ion extraction. There have been simulations of neat liquid-liquid interfaces and on liquid-liquid or liquid-air interfaces with ionic or neutral solutes Recent accounts on microscopic views of chemical reactions and solvation at liquid interfaces can be found in ref. Simulations involving extractant molecules have been reported in ref. Some results are summarized here, together with new data, obtained from molecular dynamics (MD) simulations. 

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