New Insights into the Use of (TD-)DFT for Geometries and Electronic Structures of Constrained π-Stacked Systems: [<i>n</i>.<i>n</i>]Paracyclophanes
Bibliographic record
Abstract
We have evaluated the performance of three (TD-)DFT functionals with the 6-31+G(d,p) basis set for the reproduction of experimental geometries, vertical ionization potentials, and low excitation energies of a selection of [2.2] and [3.3]paracyclophanes. Overall, (TD-)BH&H outperforms both (TD-)B3LYP and (TD-)PBE0. Some shortcomings are shown by B3LYP for geometries and by BH&H for ionization potentials. Most notably, whereas TD-B3LYP and TD-PBE0 reproduce the wavelength for the first electronic excitation of [n.n]paracyclophanes with weakly interacting aromatic rings, neither handles the strong donor-acceptor interactions in certain substituted [n.n]paracyclophanes, and both seriously underestimate the energy for their first electronic excitation. As the former systems are in many ways similar to stacked nucleic acid bases, we recommend the use of (TD-)PBE0/6-31+G(d,p) for further studies on pi-stacking interactions in constrained systems, such as the base pairs in oligonucleotides.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".