Formation and Reactivity of 3-Diazopyridinium Cations and Influence on Their Reductive Electrografting on Glassy Carbon
Bibliographic record
Abstract
The in situ generation of 3-diazonium cations from 3-aminopyridine and their subsequent stability under experimental conditions used for electrografting of pyridine groups were investigated by spectroscopy and electrochemistry. UV spectroscopy revealed the rapid kinetics for the reaction of 3-aminopyridine with sodium nitrite in HCl to form the 3-diazopyridinium cation with a second-order rate constant of 550 ± 20 L mol(-1) s(-1) at 22 °C. UV spectroscopy showed that the 3-diazopyridinium ion was relatively unstable and its transformation into 3-hydroxypyridine was proven by (1)H NMR. Its hydrolytic decomposition was investigated by NMR and followed first-order kinetics with a rate constant of (53 ± 5) × 10(-3) s(-1) at 22 °C. These results enable us to establish the appropriate conditions for the electrografting of pyridine from the corresponding diazonium cations generated in situ. The electrochemical modification of glassy carbon electrodes with pyridine was characterized by cyclic voltammetry and the resulting grafted layer by electrochemical impedance spectroscopy in the presence of Fe(CN)(6)(3-/4-) as redox probes. The effect of diazotization time before electrochemical reduction on the blocking effect of the grafted layer was investigated and showed that an increase of the diazotization time led to less efficient grafting. The presence of immobilized pyridine on the electrode surface was demonstrated by X-ray photoelectron spectroscopy measurements, and a surface coverage of 8.8 × 10(-10) mol cm(-2) was estimated for the grafted pyridine groups. The significance of these results for researchers using the in situ generation approach for electrochemical and chemical grafting is discussed.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".