Synthesis of a Novel Series of 6,6'‐Disubstituted 4,4'‐Bipyrimidines by Radical Anion Coupling: New π‐Accepting Ligands for Coordination Chemistry
Bibliographic record
Abstract
Abstract A new family of 6,6'‐disubstituted 4,4'‐bipyrimidine ligands has been prepared and characterized. The reduction potentials of the new ligands, as determined by cyclic voltammetry, indicate that these new ligands are considerably better π‐acceptors than the ubiquitous 2,2'‐bipyridine ligand, and are even superior to the parent unsubstituted 4,4'‐bipyrimidine ligand. The substituents in 6,6' positions of the 4,4'‐bipyrimidine also cause a red‐shift in the π→π* and n→π* absorptions throughout the UV region. The X‐ray crystal structure of one member of the family of bipyrimidines demonstrates that the aryl substituents may lie coplanar with the pyrimidine rings in the solid state. The additional electron delocalization afforded by the aryl substituents on the pyrimidine rings contribute to the better π‐accepting ability of these compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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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 | 0.001 | 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".