Coupled Electron/Proton Transfer Studies of Benzoquinone-Modified Monolayers
Bibliographic record
Abstract
The electrochemical reduction of benzoquinone involves a coupled transfer of protons and electrons. Theoretical treatments of proton-coupled electron transfer (PCET) indicate that both thermodynamic (apparent formal potential) and kinetic (apparent standard heterogeneous rate constants) quantities should be highly pH-dependent. Although there are several reports of quinone-derivatized self-assembled monolayers (SAMs) in the literature, no systematic studies on the pH dependence of the PCET kinetics have been reported. In this work, we outline a method to produce SAM-aminobenzoquinone monolayers starting from diluted monolayers of an amine-terminated SAM. The electroactive monolayer behaves as a nearly ideal Nernstian system (no interactions between redox centers). In neutral to weakly acidic electrolytes, the aminobenzoquinone can be reduced in a kinetically slow, two-electron, two-proton (2e2H) process, but in lower pH solutions, the observed reaction is consistent with an overall 2e3H transfer. Kinetic measurements have been made using techniques that do not rely on the assumption of a potential-independent apparent transfer coefficient. The apparent standard rate constants range from 0.1 to 0.01 s −1, which is roughly an order of magnitude faster than previous reports for comparable systems. Plots of log( k s,app ) versus pH are distorted variants of the expected W plots predicted from the theory of 2e2H PCET. These deviations may be caused by surface p K a effects and/or additional reaction pathways arising from the third proton transfer.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".