Near-Infrared Absorbing Azo Dyes: Synthesis and X-ray Crystallographic and Spectral Characterization of Monoazopyrroles, Bisazopyrroles, and a Boron−Azopyrrole Complex
Why this work is in the frame
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Bibliographic record
Abstract
Symmetric 2,5-bisazopyrroles 2(a-d) were synthesized by a one-step reaction of substituted phenyl diazonium salts [R'(Ph)N2(+)Cl-] [a, R' = 4-N(CH3)2; b, R' = 2-OH; c, R' = 2-CO2H; d, R' = 4-NO2] with pyrrole under basic conditions. Asymmetric 2,5-bisazopyrroles 3(a-d) were synthesized by reacting substituted phenyl diazonium salts [R''(Ph)N2(+)Cl-] (a, R'' = 4-OCH(3); b, R'' = H; c, R'' = 4-Br; d, R'' = 4-NO2) with 2-(4-dimethylaminophenylazo)-1H-pyrrole (1a) under the same conditions. The reactions of 2a with boron trifluoride and iodomethane provided a BF2-azopyrrole complex of 1H-pyrrolo[2,1-c]-1,2,4,5-boratriazole (4) and 2,5-bisazo-1-methylpyrrole 5. X-ray crystallographic and spectral analysis of 1a, 2a, 2b, and 4 showed that 1a has three crystal forms: 1a(I), 1a(II), and 1a(III), the latter two bearing a bicyclic ring system formed via intermolecular hydrogen bonding. Complex 4 was found to be the most planar due to a rigid trans-azo configuration and has the longest N horizontal lineN bond distances (1.322 and 1.300 Angstrom) and wavelength of maximum absorption (754 nm). The N horizontal lineN bond distances increase in the sequence of monoazopyrrole [1a(I): 1.253 Angstrom], bisazopyrrole (2a: 1.283 Angstrom), bisazopyrrole with intramolecular hydrogen bonding (2b: 1.293 and 1.293 Angstrom), and the BF2-azopyrrole complex. Their maximum absorptions shift bathochromically in the sequence of monoazopyrrole (1a: 443 nm), bisazopyrroles [2(a-d), 3(a-d), 5: 486-615 nm], and the BF2-azopyrrole complex. These results are important for the design of near-infrared absorbing azo dyes and suggest an efficient path for the preparation of near-infrared absorbing azo dyes by effectively enhancing pi-electron delocalization.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 it