Electronic Structure and Reactivity of One-Electron-Oxidized Copper(II) Bis(phenolate)–Dipyrrin Complexes
Bibliographic record
Abstract
The sterically hindered bis(phenol)–dipyrrin ligands HLH3 and PhLH3 were reacted with 1 equiv of copper(II) under ambient conditions to produce the copper radical complexes [Cu(HL)] and [Cu(PhL)]. Their X-ray crystal structures show relatively short C–O bond distances (mean bond distances of 1.287 and 1.291 Å), reminiscent of mixed pyrrolyl–phenoxyl radical species. Complexes [Cu(HL)] and [Cu(PhL)] exhibit rich electronic spectra, with an intense near-IR (NIR) band (ε > 6 mM–1 cm–1) at 1346 and 1321 nm, respectively, assigned to a ligand-to-ligand charger-transfer transition. Both show a reversible oxidation wave (E1/21,ox = 0.05 and 0.04 V), as well as a reversible reduction wave (E1/21,red = −0.40 and −0.56 V versus ferrocenium/ferrocene, respectively). The cations ([Cu(HL)]+ and [Cu(PhL)]+) and anions ([Cu(HL)]– and [Cu(PhL)]–) were generated. They all display an axial (S = 1/2) signal with a copper hyperfine structure in their electron paramagnetic resonance spectra, consistent with ligand-centered redox processes in both reduction and oxidation. Complex [Cu(HL)](SbF6) was cocrystallized with [Cu(HL)]. Oxidation is accompanied by a slight contraction of both the C–O bonds (mean bond distance of 1.280 Å) and the C–C bonds connecting the peripheral rings to the dipyrrin. The cations show vis–NIR bands of up to 1090 nm due to their quinoidal nature. The anions do not show a significant band above 700 nm, in agreement with their bis(phenolate)–dipyrrin character. The radical complexes efficiently catalyze the aerobic oxidation of benzyl alcohol, 1-phenylethanol, and unactivated 2-phenylethanol in basic conditions.
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How this classification was reachedexpand
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) | 0.003 | 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 teacher head, 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".