Mono- and Dinuclear Ruthenium Carbonyl Complexes with Redox-Active Dioxolene Ligands: Electrochemical and Spectroscopic Studies and the Properties of the Mixed-Valence Complexes
Bibliographic record
Abstract
The mononuclear complex [Ru(PPh(3))(2)(CO)(2)(L(1))] (1; H(2)L(1) = 7,8-dihydroxy-6-methoxycoumarin) and the dinuclear complexes [[Ru(PPh(3))(2)(CO)(2)](2)(L(2))][PF(6)] [[2][PF(6)]; H(3)L(2) = 9-phenyl-2,3,7-trihydroxy-6-fluorone] and [[Ru(PBu(3))(2)(CO)(2)](2)(L(3))] (3; H(4)L(3) = 1,2,3,5,6,7-hexahydroxyanthracene-9,10-dione) have been prepared; all complexes contain one or two trans,cis-[Ru(PR(3))(2)(CO)(2)] units, each connected to a chelating dioxolene-type ligand. In all cases the dioxolene ligands exhibit reversible redox activity, and accordingly the complexes were studied by electrochemistry and UV/vis/NIR, IR, and EPR spectroscopy in their accessible oxidation states. Oxidation of 1 to [1](+) generates a ligand-centered semiquinone radical with some metal character as shown by the IR and EPR spectra. Dinuclear complexes [2](+) and 3 show two reversible ligand-centered couples (one associated with each dioxolene terminus) which are separated by 690 and 440 mV, respectively. This indicates that the mixed-valence species [2](2+) has greater degree of electronic delocalization between the ligand termini than does [3](+), an observation which was supported by IR, EPR, and UV/vis/NIR spectroelectrochemistry. Both [2](2+) and [3](+) have a solution EPR spectrum consistent with full delocalization of the unpaired electron between the ligand termini on the EPR time scale (a quintet arising from equal coupling to all four (31)P nuclei); [3](+) is localized on the faster IR time scale (four CO vibrations rather than two, indicative of inequivalent [Ru(CO)(2)] units) whereas [2](2+) is fully delocalized (two CO vibrations). UV/vis/NIR spectroelectrochemistry revealed the presence of a narrow, low-energy (2695 nm) transition for [3](+) associated with the catecholate --> semiquinone intervalence transition. The narrowness and solvent-independence of this transition (characteristic of class III mixed-valence character) coupled with evidence for inequivalent [Ru(CO)(2)] termini in the mixed-valence state (characteristic of class II character) place this complex at the class II-III borderline, in contrast to [2](2+) which is clearly class III.
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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 | 0.001 | 0.001 |
| 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".