Excited State Intramolecular Proton Transfer (ESIPT) from Phenol to Carbon in Selected Phenylnaphthols and Naphthylphenols
Bibliographic record
Abstract
ESIPT and solvent-assisted ESPT in isomeric phenyl naphthols and naphthyl phenols 5-8 were investigated by preparative photolyses in CH3CN-D2O, fluorescence spectroscopy, LFP, and ab initio calculations. ESIPT takes place only in 5 (D-exchange Φ = 0.3), whereas 6-8 undergo solvent-assisted PT with much lower efficiencies. The efficiency of the ESIPT and solvent-assisted PT is mainly determined by different populations of the reactive conformers in the ground state and the NEER principle. The D-exchange experiments and calculations using RI-CC2/cc-pVDZ show that 5 in S1 deactivates by direct ESIPT from the OH to the naphthalene position 1 through a conical intersection with S0, delivering QM 14 that was detected by LFP (τ = 26 ± 3 ns). ESIPT to position 3 in 5 is possible but it proceeds from a less-populated conformer and involves an energy barrier on S1. In solvent-assisted PT to naphthalene position 4 in 5, zwitterion 17 is formed, which cyclizes to stable naphthofuran photoproducts 9-12. The regiochemistry of the deuteration in solvent-assisted PT was correlated with the NBO charges of the corresponding phenolates/naphtholates 5(-)-8(-). Combined experimental and theoretical data indicate that solvent-assisted PT takes place via a sequential mechanism involving first deprotonation of the phenol/naphthol, followed by the protonation by H2O in the S1 state of phenolate/naphtholate. The site of protonation by H2O is mostly at the naphthalene α-position.
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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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".