Direct-dynamics approach to catalytic effects: The tautomerization of 3-hydroxyisoquinoline as a test case
Bibliographic record
Abstract
The mechanism of tautomerization of 3-hydroxyisoquinoline (3HIQ) in its first excited singlet state is studied theoretically for the isolated molecule and the 1:1 complexes with water (3HIQ/H2O) and acetic acid (3HIQ/AA). It is found that the proton transfer is a tunneling process which is strongly mediated by the motion of the heavier atoms involved in the hydrogen bond bridges. Therefore it is argued that quantitative assessment of the tremendous catalytic effect of complexation observed experimentally is possible only through the evaluation of multidimensional tunneling rate constants. These are addressed using a direct dynamics approach based on the multidimensional instanton model. The potential energy surface, which governs the tautomerization dynamics, is generated from ab initio calculations at CIS/6-31G* and CASSCF(8,8)/6-31G* levels of theory. It is formulated in terms of the normal modes of the transition state and consists of 33, 57, and 72 degrees of freedom for 3HIQ, 3HIQ/H2O, and 3HIQ/AA, respectively. The catalytic effect of complexation is discussed as an interplay between the static component, reflected in the change of geometries and relative stabilities of the three stationary points, and the dynamic one, resulting from the effects of coupling of the tunneling motion to the skeletal modes. Since the coupling parameters reported in the present study are typical for proton transfer along hydrogen bridges, the relative weight of these effects in the overall acceleration of the reaction will be larger in complexes with smaller reduction of the barrier height upon complexation.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".