Dynamic hyperconjugation induced bond-angle rotation isomerization mechanism and anionic conformational rigidity-dependent melting points of ionic liquids
Bibliographic record
Abstract
The pyramidal inversion of trisubstituted heteroatoms is well-recognized. However, the stereochemistry of bicoordinated heteroatoms is poorly developed and few examples assumedly isomerize by double-torsion motion or bond-angle inversion. Here, by using ab initio molecular dynamics combined with metadynamics simulation, we reveal an unexpected competing isomerization mechanism, namely dynamic π → σ* negative hyperconjugation induced coupled rotation of bond and bond angle leads to helix inversion in bis(trifluoromethane)sulfonamide (TFSI-), making TFSI- follow four distinct trans-cis isomerization pathways with diverse energy barriers (12–52 kJ mol-1) which are significantly higher than 3.6 kJ mol-1 of sole pathway estimated by conventional static calculations. Our quantitative simulations and experiments results confirm the positive correlation between overall stability of cis-TFSI- with polarity of countercations. The melting points (Tm) of TFSI--based ionic liquids (ILs) linearly rise with the conformational rigidity of TFSI- in the ion pair state, offering a new fundamental perspective on the origin of low Tm of ILs.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".