Evaluation of the Extent of Conjugation in Symmetrical and Asymmetrical Aryl-Substituted Acetophenone Azines Using Electrochemical Methods
Bibliographic record
Abstract
The electrochemical behavior of a series of symmetrical and unsymmetrical aryl-substituted acetophenone azines (1-X/Y, where X and Y are 4-NO2, 4-CN, H, 3-OCH3, 4-OCH3, 4-CH3, and 4-N(CH3)2) was studied in acetonitrile and N,N-dimethylformamide (DMF) solution using cyclic voltammetry (CV). Compounds 1-X/Y, where neither X or Y are nitro substituents, undergo successive reduction to their radical anion (1-X/Y.-) and then dianion (1-X/Y2-), respectively. In all cases, the formation of the radical anion is completely reversible and the standard reduction potentials, Eo1-X/Y/1-X/Y.- could be determined. The reversibility of the second electron transfer is substituent dependent with certain dianions sufficiently basic to be protonated under our conditions. Standard reduction potentials (Eo1-X/Y/1-X/Y.-) for the formation of radical anions exhibit a large substituent effect with values differing by more than 0.66 V throughout the series going from 1-4-CN/4-CN to 1-4-OCH3/4-OCH3; similar substituent effects were determined for the formation of the dianion. The nitro-containing azines deviate from the above-mentioned behavior. With the exception of 1-4-NO2/4-NO2, they exhibit single electron waves that have values of Eo1-X/Y/1-X/Y.- within 40 mV of each other and thus the reduction is not subject to the same substituent effect as the other azines. 1-4-NO2/4-NO2 exhibits an Eo at a similar potential, but is a two-electron reversible wave with features indicative of a reduction system containing two localized, nonconjugated redox centers. The reduction potentials of all the aryl azines were correlated with Hammett sigma parameters to look at variations in Eo1-X/Y/1-X/Y.- vs SCE as a function of substituent. The small rho values in combination with the other electrochemical data provide support for single bond character of the N-N bond and evidence for a lack of strong electronic communication between the two aryl centers through the azomethine bonds, especially for those systems with electron-withdrawing groups.
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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) | 0.000 | 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".