Theoretical approach to photochromism of aromatic Schiff bases: A minimal chromophore salicylidene methylamine
Bibliographic record
Abstract
The ground and excited electronic states conformations of various tautomers of salicylidene methylamine (SMA) are calculated by ab initio methods. It is demonstrated that the cis-keto form, more stable in the ππ* S1 state, can rapidly decay to a strongly nonplanar configuration of the nπ* state, which subsequently undergoes very fast internal conversion to one of the trans-keto tautomers. This we identify with the photochromic species of SMA. The calculated photochromic absorption spectrum reproduces very well the observed spectrum. The rates of the proton transfer processes in the ground and excited states of SMA are calculated with the help of the ab initio geometries, force fields, and the instanton method. It is shown that the excited state proton transfer occurs faster than 50 fs for the CIS barrier of 1.6 kcal/mol. The ground state backproton transfer between the cis-keto and enol tautomers is predicted to take ∼30 ps and to exhibit a large deuterium effect.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".