Non-innocent ligand behaviour of a bimetallic Cu complex employing a bridging catecholate
Bibliographic record
Abstract
The geometric and electronic structure of a bimetallic Cu Schiff-base complex and its one-electron oxidized form have been investigated. The two salen units in the neutral complex 1 are linked via a bridging catecholate function, and the coupling between the two Cu(II) d(9) centres was determined to be weakly antiferromagnetic on the basis of solid-state magnetic studies (J = -3 cm(-1)), and variable-temperature electron paramagnetic resonance (EPR) (J = -3 cm(-1)). Theoretical calculations (DFT) were in agreement with the experimental results (J = -7 cm(-1)), and provided insight into the coupling mechanism for the neutral system. One-electron oxidation provided [1](+) which was observed to have limited stability in solution. The oxidized complex was determined to be a ligand radical species in solution, with the electron hole potentially localized on the redox-active dioxolene, the phenolate ligands, or delocalized over the entire ligand system. Electrochemical experiments and UV-vis-NIR spectroscopy, in combination with density functional theory (DFT) calculations, provided insight into the locus of oxidation and the degree of delocalization in this system. The ligand radical for [1˙](+) was determined experimentally to be localized on the dioxolene bridge with a small amount of spin density on the outer phenolate moieties predicted by the calculations. This assignment was aided via comparison to data for the Ni analogue (Inorg. Chem., 2011, 50, 6746). The resonance Raman spectrum of [1˙](+) (λ(ex) = 413 nm) in CH(2)Cl(2) solution clearly exhibited a new band at 1308 cm(-1) in comparison to 1, supporting semiquinone formation. Variable-temperature EPR on the three-spin system [1˙](+) did not provide definitive information on the coupling interaction, possibly due to a very small difference in energy between the S = 3/2 and S = 1/2 states and/or a very small zero-field splitting, in combination with significant line-broadening. The data is consistent with a description of the overall electronic structure of [1˙](+) as a bimetallic Cu(II) complex with a bridge-localized semiquinone ligand radical species.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.001 | 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".