A Transient EPR Study of Electron Transfer in Tetrathiafulvalene-Aluminum(III) Porphyrin-Anthraquinone Supramolecular Triads
Bibliographic record
Abstract
Abstract The stabilization of light-induced charge separation in two axially bound triads based on aluminum(III) porphyrin (AlPor) are investigated using the electron spin polarization patterns of the final radical pair state. In the triads, TTF-(Ph) n -py-AlPor-AQ, (n=0, 1) anthraquinone (AQ) is attached covalently to the Al(III) center, while the donor tetrathiafulvalene (TTF) coordinates to Al(III) on the opposite face of the porphyrin ring via the appended pyridine (py). The dyad AlPor-AQ has been studied previously (M. Kanematsu, P. Naumov, T. Kojima, S. Fukuzumi, Chem. Eur. J. 17 (2011) 12372.) and shown to undergo fast light-induced charge separation and triplet recombination. Here, it is shown that by coordinating pyridine-appended TTF to the porphyrin, the charge separation can be stabilized. The spin polarized transient EPR spectra of the state TTF· + AQ· − can be observed in both the glass phase and in liquid solution and show that the state is formed from a singlet precursor on a timescale of less than ~0.5 ns. Using structural models to fix the geometry of the radical pair and the strength of the dipolar coupling, it is possible to determine the sign and approximate magnitude of the exchange coupling between TTF· + and AQ· − . In contrast, other similar triads, which display relatively large ferromagnetic coupling, the exchange coupling is found to be small and antiferromagnetic. This difference can be rationalized as a result of differences in the structure of the bridge between the porphyrin and the acceptor.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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 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".