Weak Interactions in the Crystal Structures of Tetraacetylenes Derived from Pentaerythrityl Tetraphenyl Ether
Bibliographic record
Abstract
Tetrakis(4-ethynylphenyl)methane ( 7 ) is known to crystallize as an interpenetrated diamondoid network held together in part by weak C⋮C H···C⋮C interactions that define characteristic cyclic quartets of ethynyl groups. To test the ability of this motif to direct the crystallization of more flexible molecules, we synthesized a series of tetraacetylenes derived from pentaerythrityl tetraphenyl ether, and we solved their structures by X-ray diffraction. Pentaerythrityl tetrakis(4-ethynylphenyl) ether ( 4 ) and the more rigid analogue 7 crystallize isostructurally, even though their cores are significantly different in size and flexibility. This observation shows that C⋮C H···C⋮C interactions may have value in engineering molecular crystals. However, widely different structures are obtained by crystallizing pentaerythrityl tetrakis(3-ethynylphenyl) ether ( 5 ) and pentaerythrityl tetrakis(4‘-ethynyl-1,1‘-biphenyl-4-yl) ether ( 6 ), despite their close similarity to tetraacetylene 4 . The unpredictably varied behavior of tetraacetylenes 4 − 7 highlights the difficulty of engineering crystals built from molecules that are flexible and unable to form dominant directional interactions.
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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 | 0.001 |
| 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 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".