The relaxation of electronically excited molecules: Effects of alkyl substitution on the S2 and T1 states of benzopyranthione in solution
Bibliographic record
Abstract
The effects of n-alkyl group substitution on the photophysics, photochemistry and spectroscopy of benzopyranthione (BPT), a rigid model aromatic thione, have been investigated. The absorption, emission and excitation spectra of BPT and its 2-substituted n-C4H9 (I) and n-C10H21 (II) derivatives, their S2 → S0 fluorescence and T1 → S0 phosphorescence quantum yields and their S2 and T1 lifetimes have been measured in several solvents, in the presence and absence of oxygen. Perfluorinated solvents have been used to minimize the effects of solute–solvent interactions on the excited state dynamics. The rate constants of radiative and non-radiative decay of the S2 and T1 states and of their bimolecular quenching by molecular oxygen and by ground state thione have been obtained. The spectra of I and II are nearly identical in every respect, except that the S2←S0 absorption spectrum of II exhibits a greater absorbance on its red edge, attributable to its larger density of low-frequency torsional states. The expected effect of intramolecular interaction of the longer alkyl chain with the strongly H-abstracting CS group was not observed in the S2 states of II compared with I, and this lack of effect was confirmed by showing that the excited state lifetimes were unaffected by a 40-fold change in the viscosity of the perfluoroalkane solvents. By contrast, a significantly shorter lifetime of the triplet state of II compared with I suggests that intramolecular interaction beween the hydrocarbon tail of II and the excited CS group may induce non-radiative relaxation in the longer-lived triplets.
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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 | 0.001 |
| 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".