Cation−π and π–π Interactions in Aqueous Solution Studied Using Polarizable Potential Models
Bibliographic record
Abstract
Polarizable potential models for the interaction of Li(+), Na(+), K(+), and NH4(+) ions with benzene are parametrized based on ab initio quantum mechanical calculations. The models reproduce the ab initio complexation energies and potential energy surfaces of the cation-π dimers. They also reproduce the cooperative behavior of "stacked", cation-π-π trimers and the anticooperative behavior of "sandwiched", π-cation-π trimers. The NH4(+) model is calibrated to reproduce the energy of the NH4(+)-H2O dimer and yields correct free energy of hydration and hydration structure without further adjustments. The models are used to investigate cation-π interactions in aqueous solution by calculating the potential of mean force between each of the four cations and a benzene molecule and by analyzing the organization of the solvent as a function of the cation-benzene separation. The results show that Li(+) and Na(+) ions are preferentially solvated by water and do not associate with benzene, while K(+) and NH4(+) ions bind benzene with 1.2 and 1.4 kcal/mol affinities, respectively. Molecular dynamics simulations of NH4(+) and of K(+) in presence of two benzene molecules in water show that cation-π and π-π affinities are mutually enhanced compared to the pairwise affinities, confirming that the cooperativity of cation-π and π-π interactions persists in aqueous solution.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".