Solvatation

Résumé

vignette|Un ion sodium solvaté par des molécules d'eau. La solvatation est le phénomène physico-chimique observé lors de la dissolution d'une substance chimique dans un solvant. Lors de l'introduction d'une espèce chimique initialement à l'état solide (sous forme de cristal ou amorphe), liquide ou gazeux dans un solvant, les atomes, ions ou molécules de l'espèce chimique se dispersent dans la solution et interagissent avec les molécules de solvant. Cette interaction s'appelle la solvatation. Elle est de différente nature suivant le soluté et le solvant et recouvre des phénomènes aussi différents que des interactions ion-dipôle (soluté : Na+, solvant : eau), des liaisons hydrogène (soluté alcool, solvant eau) ou des liaisons de van der Waals (soluté méthane, solvant cyclohexane). Quand le soluté est en phase condensée (liquide ou solide), la solvatation entre dans le bilan énergétique qui met en jeu la séparation des molécules ou des ions dans le soluté avant sa dispersion dans le sol

Source officielle

https://fr.wikipedia.org/wiki/Solvatation

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Towards a Composite Benchmark Method for the Aqueous Solvation Free Energies of Organic Compounds

Daniel David Sadowsky

Water is ubiquitous in the biosphere, and the difficulty of rigorously treating the effects of aqueous solvation currently limits the widespread use of computational methods in many areas of environmental chemistry. We propose an approach to benchmark calculations of aqueous free energies of solvation based on molecular dynamics simulation which is derived from first principles, statistical mechanically complete, and systematically improvable. The approach partitions the solvation free energy into the free energies of solvent density change, solvent cavity organization, and solvent-solute interaction, each of which is computed from first principles. A composite approach is considered for the calculation of the contributions of quantum nuclear effects to solvation free energies and the contributions of electron correlation and relativistic effects to solvent-solute interactions.

2015

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Voltage sensors based on the solvatochromic molecule Nile Red

Nicole Vassalli

2015

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Microscopic Picture of the Solvent Reorganization During Electron Transfer to Flavin in Water

Murat Kiliç

The redox potential of molecular species is largely modulated by its molecular environment so that a change of the environment will lead to a different redox potential. However, a detailed molecular picture of reorganization of the environment upon reduction is still unclear. To unravel the details of the solvent reorganization during electron transfer, we have performed density functional theory-based molecular dynamics (DFT-MD) and hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of the reduction of lumiflavin. Previously, we have calculated the reduction free energy curves of the redox half reactions of lumiflavin in water as a function of the instantaneous gap energy (Delta E) (J. Chem. Theory Comput. 2013, 9, 3889-3899). In this work, we focus on finding the changes in the solvent environment that correlate with this Delta E reaction coordinate. Comparing the QM/MM simulations, in which the solvent is modeled with an empirical force field, with the (full) DFT-MD simulations, we find that the response through electronic polarization plays a significant role in the latter case. Also a small charge transfer between flavin and solvent is observed in the full DFT treatment. As a result, we find only in the case of the QM/MM model a strong correlation between Delta E and the (pairwise computed) electrostatic potential (ESP) at the flavin due to the solvent. By analyzing the contribution of the ESP at the flavin per solvent molecule, we cannot only distinguish between the different modes of hydration by solvent molecules that coordinate at the hydrophilic and hydrophobic sides of the flavin molecule but also quantify their contribution to the reorganization free energy by measuring the ESP fluctuations per solvent molecule.

AMER CHEMICAL SOC2019

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