Hydrogen-bonding behaviour of benzene-1,2,4,5-tetracarboxylic acid: supramolecular structures of different dimensionality in the 2:1 adducts formed with 4,4′-bipyridyl and hexamethylenetetramine
Bibliographic record
Abstract
Co-crystallization of benzene-1,2,4,5-tetracarboxylic acid, C10H6O8, with 4,4'-bipyridyl, C10H8N2, or with hexamethylenetetramine, C6H12N4, from methanol solutions yields in each case a 2:1 salt, [(C10H9N2)+]2.[(C10H4O8)2-] (1) and [(C6H13N4)+]2.[(C10H4O8)2-] (2). In (1) the carboxylate anions lie across centres of inversion, but they contain no intramolecular O-H...O hydrogen bonds: the cations and anions are linked by strong O-H...N and N-H...O hydrogen bonds into a chain-of-rings, and these chains are further linked into a three-dimensional framework structure by means of C-H...O hydrogen bonds and aromatic pi...pi stacking interactions. Compound (2) contains two independent three-molecule aggregates, comprising a central anion and two cations, linked to the anion by means of short N-H...O hydrogen bonds. One of these aggregates is centrosymmetric, but the other is not, and the two types of anion both form two intramolecular O-H...O hydrogen bonds. The two types of three-molecule aggregate, in which all the anions are virtually parallel, are linked by short C-H...O hydrogen bonds into a molecular staircase.
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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".