Redox potential tuning in bio-relevant heterocycles via (anti)aromaticity modulated H-bonding (AMHB)
Bibliographic record
Abstract
Hydrogen bonds are arguably the most important non-covalent interactions in chemistry and biology, and their strength and directionality have been elegantly exploited in the rational design of complex structures. We recently noted that the variable responses of cyclic π-systems upon H-bond formation reciprocally lead to modulations of the H-bonds’ strengths, a phenomenon that we dubbed (anti)aromaticity-modulated hydrogen bonding (AMHB) [J. Am. Chem. Soc. 2016, 138, 3427–3432]. Species that switch from aromatic to antiaromatic or vice versa upon changing π-electron counts should be oppositely stabilized by the AMHB effects, so their redox potentials should be significantly “tuned” by H-bond formation. Herein, using quantum chemical simulations, we explore the effects of these H-bond induced π-electron polarizations on the redox potentials of (anti)aromatic heterocycles. The systems chosen for this study have embedded amide groups and amidine moieties capable of forming two-point H-bonds in their cyclic π-systems. Thus, as the 4-electron and 6-electron π-systems in redox-capable monocycles (e.g., quinones) can be differentially stabilized, their redox potentials can be modulated by H-bond formation by as much as 6 kcal/mol (258 mV for one electron transfer). In fused rings, the connectivity patterns are as important as the π-electron counts. Extending these ideas to flavin, a biologically relevant case, we find that H-bonding patterns like those found in its crystals can vary its redox potential by up to 1.3 kcal/mol.
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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 | 0.001 |
| 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 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".