Location of the Fluoride Ion in Tetrapropylammonium Fluoride Silicalite-1 Determined by <sup>1</sup>H/<sup>19</sup>F/<sup>29</sup>Si Triple Resonance CP, REDOR, and TEDOR NMR Experiments
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Bibliographic record
Abstract
The location of the fluoride ion in tetrapropylammonium fluoride silicalite-1 ([TPA]-F-[Si-MFI]), an as-synthesized siliceous zeolite with the MFI topology, has been unambiguously determined using solid-state NMR experiments alone. With the 1 H→ 29 Si CP-INADEQUATE experiment, the 12 peaks in the highly resolved 29 Si MAS NMR spectrum of [TPA]-F-[Si-MFI] were assigned. Using these peak assignments it was possible to perform 1 H/ 19 F/ 29 Si triple resonance CP, REDOR, and TEDOR experiments to measure F−Si distances and thus locate the fluoride ion. It is covalently bonded to Si-9 in the [4 1 5 2 6 2 ] cage of the zeolite framework and exchanges between two “mirror-related” Si-9 sites, making them equivalent on the NMR time scale. The importance of this result and the general applicability of the approach are discussed.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| 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)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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