Influence of alkali metal cations on the photoheterolysis of 9-cyclopropyl-9-fluorenol and the reactivity of the 9-cyclopropyl-9-fluorenyl cation in non-acidic zeolites
Bibliographic record
Abstract
Alkali metal cation regulation of carbocation formation and reactivity in non-acidic zeolites is probed using the photoheterolysis reaction of 9-cyclopropyl-9-fluorenol. Nanosecond time-resolved diffuse reflectance is employed to directly observe the 9-cyclopropyl-9-fluorenyl cation as a transient species within the non-acidic zeolites. The efficiency of carbocation formation via photoheterolysis and the dynamics of other reaction pathways available to photoexcited 9-cyclopropyl-9-fluorenol are found to be strongly dependent on the zeolite alkali metal counterion. In particular, the yield of carbocation decreases with increasing counterion size in a manner consistent with the zeolite assisting the excited state CO bond cleavage via Lewis acid catalysis involving the metal cation. Zeolite encapsulation is also found to modulate the ability of water and methanol to assist photoheterolysis. For instance, the influence of coadsorbed water on the photoheterolysis reaction within zeolites is found to be highly sensitive to the alkali metal cation. The rate constant for intrazeolite decay of the 9-cyclopropyl-9-fluorenyl cation increases significantly as the alkali metal cation size increases and as the SiAl ratio decreases. These reactivity trends suggest that the intrazeolite decay of the 9-cyclopropyl-9-fluorenyl cation involves nucleophilic addition at the active site [Si-O-Al] bridges of the zeolite framework. In addition, the reactivity of the 9-cyclopropyl-9-fluorenyl cation within alkali metal zeolites can be regulated by the co-inclusion of reagents such as methanol, water, and 1,1,1,3,3,3-hexafluoro-2-propanol.Key words: cation-exchanged zeolites, 9-cyclopropyl-9-fluorenyl cation, laser photolysis, reactivity.
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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 | 0.000 |
| 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) | 0.001 | 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".