Molecular conformation of linear alkane molecules: From gas phase to bulk water through the interface.

We studied the behavior of long chain alkanes (LCAs) as they were transferred from gas to bulk water, through the liquid-vapor interface. These systems were studied using umbrella sampling molecular dynamics simulation and we have calculated properties like free energy profiles, molecular orientation, and radius of gyration of the LCA molecules. The results show changes in conformation of the solutes along the path.

Critical effects on attractive solutes in binary liquid mixtures close to their consolute point: a new experimental strategy.

The effect of near-criticality upon the properties of dilute solutions of attractive solutes has been previously studied only using pure solvents close to the vapor-liquid critical point. The experimental difficulties that plague this thermodynamic region have somewhat obscured the interpretations of the results. Consequently, the coupling of long-range critical fluctuations with short-range intermolecular interactions is still a matter of debate.

Is ammonia a better solvent than water for contact ion pairs?

The existence of a charge-transfer-to-solvent process when a KI contact ion pair (CIP) dissolved in supercritical water (SCW) is excited by UV light was confirmed by use of electronic structure calculations applied to molecular dynamics trajectories. We observed similar behavior with fluid density as that found for the KI-CIP in supercritical ammonia (SCA); nevertheless, there are some distinct features in the two supercritical solvents. First, the effect of the solvent field due to the molecules lying beyond the first solvation shell is very different in SCW compared with that observed in SCA; in SCW it actually has a destabilizing effect over the ground and excited states.

Solubility of solids in near-critical conditions: effect of a third component.

The effect of cosolvents on the solubility equilibria near the critical end-point of binary mixtures is analyzed. The problem has received recent attention for the particular case of ionic cosolvents (Mazo, R. M.

Development of the charge-transfer-to-solvent process with increasing solvent fluid density: the effect of ion pairing.

The study of the UV spectroscopic behaviour of alkali metal iodides dissolved in supercritical ammonia showed that two absorbing species contributed to the UV absorption of the solutions. The two species differed in the type of interaction of iodide with the cation, i.e.

Influence of ion pairing on the UV-spectral behavior of KI dissolved in supercritical NH3: from vapor phase to condensed liquid.

The UV-spectroscopic behavior of KI dissolved in supercritical ammonia enabled us to identify two species that contribute to the optical absorption depending on the fluid density rho1 and the temperature T. At low rho1 and high T, contact ion pairs (CIPs) prevail, while at high density of ammonia, solvent separated ion pairs (SSIPs) and free iodide ions dominate the optical absorption of the solute. The features of the electron excitation process depend on the state of the K+ I- species present.

Solvent triggered change of the electron excitation route of KI in supercritical NH3.

The UV-spectroscopic behavior of KI contact ion pairs (CIPs) dissolved in supercritical NH3 was studied combining classical molecular dynamics simulations with electronic structure calculations, and the results show that an abrupt change of the photoexcitation route of KI CIPs occurs at very low solvent densities. Few NH3 solvating molecules are required to hamper the well-known photoinduced intramolecular electron (e-) transfer observed in isolated ion pairs of alkali metal halides in the vapor drawing the e- to solvent cavities leading to a charge-transfer-to-solvent process.