Single-Oxidation of Ni(II) Complexes of Bidentate Fused <i>N</i>-Heterocyclic Carbene–Phenol Conjugates
Bibliographic record
Abstract
The pro-ligands (H 2 L tBu ) + and (H 2 L OMe ) + were synthesized as chloride salts. They associate an imidazo [1,5- a ] pyridinium ring and an electron-rich 2,4-(di- tert -butyl)phenol or 2-( tert -butyl)-4-methoxyphenol, respectively. The homoleptic Ni(II) complexes of H 2 L tBu ( 1 ) and H 2 L OMe ( 2 ) were prepared and structurally characterized, showing a four-coordinate nickel center with two ligands bound by one phenolate oxygen and one carbene each. Complexes 1 and 2 show two reversible oxidation waves in their cyclic voltammetry curve, at E 1/2 1 = 0.19 V and E 1/2 2 = 0.59 V, and E 1/2 1 = 0.03 V and E 1/2 2 = 0.32 V, respectively. The one-electron oxidized forms were generated and characterized by spectroscopy, while 2 + could be isolated as single crystals. They both demonstrate two remarkable NIR bands indicating radical species in CH 2 Cl 2 . The EPR parameters are 2.097, 2.023, and 1.997 (g average = 2.039) for 1 + and 2.030, 2.016, and 1.994 (g average = 2.013) for 2 + . Both g average values are slightly higher than those reported for genuine phenoxyl radicals but far below those of Ni(III) complexes, supporting a metalloradical character of 1 + and 2 +, whereby one metal d-orbital contributes to the singly occupied molecular orbital (SOMO). A very good agreement is found between DFT calculated and experimental vis–NIR and EPR data. Both metalloradical cations could be converted into Ni(III) species by addition of pyridine. The redox isomerism could be monitored by EPR spectroscopy: the [1•Py] + species exhibits for instance the g-values 2.157, 2.136, and 2.014 (g average = 2.103). The Ni(III) adducts are thermally unstable and undergo reduction back to the neutral precursor at room temperature.
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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".