(Invited) Donor-Acceptor Systems from Triplet Photosensitizers for High Potential, Long-Lived Charge Separation
Bibliographic record
Abstract
Generation of high potential, long-lived charge separated states in donor-acceptor systems are invaluable for converting light energy into either electricity or fuels. The majority of the donor-acceptor conjugates designed for this purpose are derived mainly from short-lived singlet sensitizers.1,2 In such conjugates, charge separation from the singlet excited donor or acceptor results in a short-lived charge separated state of singlet spin character. Alternatively, by utilizing high-energy triplet sensitizers one could generate long-lived charge separated states. The radical ion-pairs of triplet spin character slowly charge recombine to the ground state due to spin forbidden process. However, witnessing such a process purely from the triplet-excited state without the interference of the singlet excited state and other competing photochemical events such as excitation energy transfer has been challenging to establish.3-5 Here, we summarize our efforts to synthesize donor-acceptor conjugates bearing triplet sensitizers wherein excited state electron transfer exclusively occurs from the triplet excited state.3-6 To achieve the goal, two types of triplet sensitizers, viz., palladium and platinum porphyrins, and b-iodo functionalized BODIPYs are covalently linked to the well-known electron acceptor, fullerene, C60. Using femtosecond transient absorption studies covering wide temporal and spatial regions, and time-resolved electron paramagnetic studies, photoinduced electron transfer from 3MP* (M = Pd or Pt) to C60 in these dyads, leading to the formation of MP•+-C60 •- charge separated state of triplet spin character is demonstrated. Similarly, the role of triplet sensitizers in promoting charge separation in I2BODIPY-C60 and I2azaBODIPY-C60 dyads6 is also highlighted. 1. B. KC, F. D’Souza, Coord. Chem. Rev. 2016, 322, 104-141. 2. D’Souza, and O. Ito ‘Chem. Soc. Rev. 2012, 41, 86-96. 3. Obondi, G. N. Lim, F. D’Souza, J. Phys. Chem. C 2015, 119, 176-185. 4. Obondi, G. N. Lim, B. Churchill, P. K. Poddutoori, A. van der Est, and F. D’Souza, Nanoscale, 2016, 8, 8333-8344. 5. K. Poddutoori,Y. E. Kandrashkin, C. O. Obondi, F. D’Souza and A. van der Est, Phys. Chem. Chem. Phys. 2018, 20, 28223-28231. 6. Shao, H. B. Gobeze, V. Bandi, C. Funk, B. Heine, M. J. Duffy, V. Nesterov, P. A. Karr, F. D’Souza, ChemPhotoChem, 2020, in press.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.002 |
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".