Examination of Water Oxidation by Catalysts Containing Cofacial Metal Sites
Bibliographic record
Abstract
Abstract A series of bimetallic complexes were developed to examine how the distance between two juxtaposed {Ru(tpy)(bpy)Cl} 1+ ( 2 ; tpy = 2,2′;6′,2″‐terpyridine; bpy = 2,2′‐bipyridine) units affect catalytic behavior in the context of water oxidation. The directionality imposed by the organic backbone for each of these “Pacman” complexes elicits idealized M ··· M distances of ca. 5, 10, and 12 Å for 4 – 6 , respectively. Cyclic voltammetry indicates that intramolecular electronic communication occurs between the metal sites of 4 , while the metal fragments are essentially electrochemically isolated for 5 and 6 . Despite the disparate distances between the metal sites, each of these complexes are shown to mediate the Ce IV ‐driven oxidation of water in acidic media. Dioxygen evolution was monitored with an optical probe in the headspace of the reaction vessel, and independently verified by the detection of appropriate ratios of 18 O‐ 18 O, 18 O‐ 16 O, and 16 O‐ 16 O in GC–MS experiments using 18 O‐labeled water. A fitting of the dioxygen evolution data indicates catalytic behavior that is first‐order with respect to catalyst concentration in all cases. This finding rules out the possibility that dioxygen formation occurs independently at each metal site simultaneously, and leaves open the possibility that O–O bond formation occurs by either both metal sites acting cooperatively, or at one metal site independent of the other. Taking into account the significant electrostatic repulsion between the two metal fragments in higher oxidation levels, we contend that the latter mechanism is the more likely scenario. Notwithstanding, complex 4 generates the largest k obs values among the bimetallic series, which suggests that the close proximity of another metal may benefit catalysis. A comparison of k obs and catalytic turnover numbers (TONs) of the bimetallic systems to the mononuclear complex 2 , however, does not indicate an improvement in catalytic behavior. This is an important observation in the collective pursuit of efficient water oxidation catalysts.
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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) | 0.001 | 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 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".