Charge Asymmetry at Aqueous Hydrophobic Interfaces and Hydration Shells

Scheu, Ruediger; Rankin, Blake M.; Chen, Yixing; Jena, Kailash C.; Ben‐Amotz, Dor; Roke, Sylvie

doi:10.1002/anie.201310266

Cited by 84 publications

(96 citation statements)

References 46 publications

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“…Scheu et al 26 use the red shifted vibrational signature of the first solvation shell water molecules to argue that there is preferential hydrogen bonding with the phenyl rings leading to stronger interactions of the water with the anion over the cation. This specific interaction is supported by the RDFs.…”

Section: Resultsmentioning

confidence: 99%

“…31 DFT has also been demonstrated to reliably model the air-water interface, where the inclusion of dispersion corrections is a key advance. 32,33 Here, we set out to confirm the spectroscopic observations of Scheu et al 26 by simulation of the TA + and TB ions in water in addition to the neutral tetra-phenyl carbon (TC 0 ) solute. To this end, we establish connection with recent spectroscopic experiments in addition to computing average ion-water binding energies and net potentials demonstrating that there are substantial charge asymmetries between the TB and TA + providing strong evidence that the TATB approximation is not reliable.…”

Section: Introductionmentioning

confidence: 81%

“…This suggests that the preference for the anion is approximately twice as strong using the TATB assumption as compared to the CPA. This question has been examined recently using spectroscopic measurements 26 that probe the hydrogen bonding interaction of the water molecules with the phenyl rings of the TB molecules. This mechanism was originally suggested by Schurhammer and Wipff.…”

Section: Introductionmentioning

confidence: 99%

“…13,29 It is also unlikely that classical MD using standard charge partitioning schemes can reproduce the correct hydrogen bonding interaction with the phenyl ring as determined by spectroscopy. 26 A number of simple models have been developed to address this question. 30 These models have concluded that the anion is preferred over the cation, but the size of this preference depends on the model.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Understanding the scale of the single ion free energy: A critical test of the tetra-phenyl arsonium and tetra-phenyl borate assumption

Duignan

Baer

Mundy

2018

The Journal of Chemical Physics

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Re-examining the tetraphenyl-arsonium/tetraphenyl-borate (TATB) hypothesis for single-ion solvation free energies The Journal of Chemical Physics 148, 222830 (2018) The tetra-phenyl arsonium and tetra-phenyl borate (TATB) assumption is a commonly used extrathermodynamic assumption that allows single ion free energies to be split into cationic and anionic contributions. The assumption is that the values for the TATB salt can be divided equally. This is justified by arguing that these large hydrophobic ions will cause a symmetric response in water. Experimental and classical simulation work has raised potential flaws with this assumption, indicating that hydrogen bonding with the phenyl ring may favor the solvation of the TB anion. Here, we perform ab initio molecular dynamics simulations of these ions in bulk water demonstrating that there are significant structural differences. We quantify our findings by reproducing the experimentally observed vibrational shift for the TB anion and confirm that this is associated with hydrogen bonding with the phenyl rings. Finally, we demonstrate that this results in a substantial energetic preference of the water to solvate the anion. Our results suggest that the validity of the TATB assumption, which is still widely used today, should be reconsidered experimentally in order to properly reference single ion solvation free energy, enthalpy, and entropy. Published by AIP Publishing. https://doi

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Understanding the scale of the single ion free energy: A critical test of the tetra-phenyl arsonium and tetra-phenyl borate assumption

Duignan

Baer

Mundy

2018

The Journal of Chemical Physics

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“…In particular, at comparable sizes, anions induce a more pronounced perturbation of their hydration shells compared to cations, because they are hydrogen-bond acceptors. 17,50,113,268,282,294,[296][297][298][299][300][301][302] The same applies to small or/and multivalent ions, because they generate a stronger electric field at their surface. This more important perturbation may require the inclusion of the second hydration shell into the QM region.…”

Section: Discussionmentioning

confidence: 97%

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Hofer

Hünenberger

2018

The Journal of Chemical Physics

104

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The absolute intrinsic hydration free energy G • H + ,wat of the proton, the surface electric potential jump χ • wat upon entering bulk water, and the absolute redox potential V • H + ,wat of the reference hydrogen electrode are cornerstone quantities for formulating single-ion thermodynamics on absolute scales. They can be easily calculated from each other but remain fundamentally elusive, i.e., they cannot be determined experimentally without invoking some extra-thermodynamic assumption (ETA). The Born model provides a natural framework to formulate such an assumption (Born ETA), as it automatically factors out the contribution of crossing the water surface from the hydration free energy. However, this model describes the short-range solvation inaccurately and relies on the choice of arbitrary ion-size parameters. In the present study, both shortcomings are alleviated by performing first-principle calculations of the hydration free energies of the sodium (Na + ) and potassium (K + ) ions. The calculations rely on thermodynamic integration based on quantum-mechanical molecular-mechanical (QM/MM) molecular dynamics (MD) simulations involving the ion and 2000 water molecules. The ion and its first hydration shell are described using a correlated ab initio method, namely resolution-of-identity second-order Møller-Plesset perturbation (RIMP2). The next hydration shells are described using the extended simple point charge water model (SPC/E). The hydration free energy is first calculated at the MM level and subsequently increased by a quantization term accounting for the transformation to a QM/MM description. It is also corrected for finite-size, approximate-electrostatics, and potentialsummation errors, as well as standard-state definition. These computationally intensive simulations provide accurate first-principle estimates for G • H + ,wat , χ • wat , and V • H + ,wat , reported with statistical errors based on a confidence interval of 99%. The values obtained from the independent Na + and K + simulations are in excellent agreement. In particular, the difference between the two hydration free energies, which is not an elusive quantity, is 73.9 ± 5.4 kJ mol 1 (K + minus Na + ), to be compared with the experimental value of 71.7 ± 2.8 kJ mol 1 . The calculated values of G • H + ,wat , χ • wat , and V • H + ,wat ( 1096.7 ± 6.1 kJ mol 1 , 0.10 ± 0.10 V, and 4.32 ± 0.06 V, respectively, averaging over the two ions) are also in remarkable agreement with the values recommended by Reif and Hünenberger based on a thorough analysis of the experimental literature ( 1100 ± 5 kJ mol 1 , 0.13 ± 0.10 V, and 4.28 ± 0.13 V, respectively). The QM/MM MD simulations are also shown to provide an accurate description of the hydration structure, dynamics, and energetics. Published by AIP Publishing.

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Grundlegende Bemerkungen zur Azidität

et al. 2018

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Dieser Aufsatz beschreibt eine vereinheitlichte Sichtweise auf Brønsted‐Azidität. Zunächst wird ein Überblick über die Konzepte Azidität, Säurestärke und pH‐Wert gegeben. Anschließend wird die in der Arbeitsgruppe Krossing entwickelte pHabs‐ oder normalpnormalHnormalanormalbnormalsH2normalO ‐Skala als vereinheitlichendes Konzept mit einigen Beispielen für ihre Anwendbarkeit vorgestellt. Abgerundet wird der Aufsatz durch die Analogie zwischen Säure‐Base‐ und Redoxchemie mit der Einführung der vereinheitlichten Redoxpotentialskala peabs. Die Kombination von pHabs‐ und peabs‐Werten resultiert in der protoelektrischen Potentialkarte (Protoelectric Potential Map, PPM) als Ergebnis aktueller Forschung zur Thermochemie einzelner Ionen. Die PPM ist also ein Instrument zum Vergleich aller möglichen Säure‐Base‐ und/oder Redoxreaktionen in allen denkbaren Reaktionsmedien.

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Charge Asymmetry at Aqueous Hydrophobic Interfaces and Hydration Shells

Cited by 84 publications

References 46 publications

Understanding the scale of the single ion free energy: A critical test of the tetra-phenyl arsonium and tetra-phenyl borate assumption

Understanding the scale of the single ion free energy: A critical test of the tetra-phenyl arsonium and tetra-phenyl borate assumption

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Grundlegende Bemerkungen zur Azidität

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