Chiral <i>versus</i> racemic building blocks in supramolecular chemistry: tartrate salts of organic diamines
Bibliographic record
Abstract
In the 1:1 adducts C(12)H(10)N(2).C(4)H(6)O(6) formed between 1,2-bis(4'-pyridyl)ethene and racemic tartaric acid [(I), triclinic P1;, Z' = 1] and (2R,3R)-tartaric acid [(II), triclinic P1, Z' = 2], the ionic components are linked by hard hydrogen bonds into single sheets, which are further linked by C-H.O hydrogen bonds. In the analogous adducts C(10)H(18)N(2).C(4)H(6)O(6) formed by 4,4'-bipyridyl with racemic tartaric acid [(III), triclinic P1;, Z' = 1] and the chiral acid [(IV), monoclinic P2(1), Z' = 1], the hard hydrogen bonds generate bilayers which are again linked by C-H.O hydrogen bonds. Piperazine forms a 1:1 salt [((C(4)H(10)N(2))H(2))(2+)].[(C(4)H(4)O(6))(2-)] with (2R,3R)-tartaric acid [(V), monoclinic P2(1)] sheets, which are linked by the cations to form a pillared-layer framework. In each of the 1:2 salts formed by racemic tartaric acid with piperazine [(VI), monoclinic P2(1)/n, Z' = 0.5] and 1,4-diazabicyclo[2.2.2]octane (DABCO) [(VII), monoclinic P2(1)/n, Z' = 0.5], the cation lies across a centre of inversion, with the [(HN(CH(2)CH(2))(3)NH)(2+)] cation disordered over two sets of sites: in both (VI) and (VII) the anions form a three-dimensional framework encapsulating large voids which accommodate the cations. The salt formed between DABCO and (2R,3R)-tartaric acid [(VIII), orthorhombic P2(1)2(1)2(1), Z' = 1] has 3:4 stoichiometry and contains four different types of ion, [(HN(CH(2)CH(2))(3)NH)(2+)](2).[N(CH(2)CH(2))(3)NH](+).3(C(4)H(5)O(6))(-).C(4)H(4)O(6)(2-): the hard hydrogen bonds generate a three-dimensional framework.
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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 | 0.001 |
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".