Cosublimation: A Rapid Route Toward Otherwise Inaccessible Halogen-Bonded Architectures
Bibliographic record
Abstract
Several synthetic techniques are available for the preparation of halogen-bonded adducts, including traditional solvent-evaporation methods and mechanochemistry. With the intention of reducing solvent usage and experimental times, we establish cosublimation as a synthetic technique for preparing halogen-bonded cocrystals, focusing on the C–I···N motif involving nitrogen-containing heterocycles. We selected four common halogen-bond donors (I 2, 1,4-diiodobenzene, 1,4-diiodotetrafluorobenzene, 1,3,5-trifluoro-2,4,6-triiodobenzene) and four halogen-bond acceptors (2,3,5,6-tetramethylpyrazine, 1,4-diazabicyclo[2.2.2]octane, 2,2′-bipyridyl, 1-adamantanecarbonitrile), by virtue of their range in volatility, and explored all 16 combinations via the following methods: solvent evaporation, overnight cosublimation in a sealed glass tube using a two-zone furnace, and expedited cosublimation in a vacuum sublimation apparatus. We show that the raw crystals obtained from overnight cosublimation are of suitable quality for single-crystal X-ray diffraction, resulting in five new crystal structures, two of which are, currently, unobtainable through other methods. Of these new structures, the first halogen bond to the nitrile group of 1-adamantanecarbonitrile is reported, resulting in the formation of a supramolecular rotor in a spinning top configuration as evidenced by 13 C and 15 N solid-state NMR spectroscopy. Strikingly, the cosublimation approach overcomes an anticooperative halogen-bonding effect to produce fully saturated cocrystals of the tritopic halogen bond donor 1,3,5-trifluoro-2,4,6-triiodobenzene with 1,4-diazabicyclo[2.2.2]octane. Finally, we show that cosublimation can be used to rapidly prepare and purify bulk samples using a vacuum sublimation apparatus, enabling the scalable preparation of halogen-bonded cocrystals within 10 to 30 min using common laboratory equipment. The methods described here enable a broad exploration of the polymorphic landscape and may be extended to the facile preparation of other classes of cocrystals.
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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) | 0.001 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".