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We report high-level electronic structure calculations of electronic states in the miniSOG (for mini Singlet Oxygen Generator) photoactive protein designed to produce singlet oxygen upon light exposure. We consider a model system with a riboflavin (RF) chromophore. To better understand the photosensitization process, we compute relevant electronic states of the combined oxygen-chromophore system and their couplings. The calculations suggest that singlet oxygen can be produced both by inter-system crossing, via a triplet state of the RF(T1)×O2(3Σ− g ) character as well as by triplet excitation energy transfer via a singlet state of the same character. Importantly, the former channel produces O2(1Σ+ g ), an excited state of singlet oxygen, which is known to convert with unit efficiency into O2(1∆g) The calculations also provide evidence for the production of the triplet state of the chromophore via internal conversion facilitated by oxygen. Our results provide concrete support to previously hypothesized scenarios.
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This content will become publicly available on November 21, 2025
Morphology- and crystal packing-dependent singlet fission and photodegradation in functionalized tetracene crystals and films
Singlet fission (SF) is a charge carrier multiplication process that has potential for improving the performance of (opto)electronic devices from the conversion of one singlet exciton S1 into two triplet excitons T1 via a spin-entangled triplet pair state 1(TT). This process depends highly on molecular packing and morphology, both for the generation and dissociation of 1(TT) states. Many benchmark SF materials, such as acenes, are also prone to photodegradation reactions, such as endoperoxide (EPO) formation and photodimerization, which inhibit realization of SF devices. In this paper, we compare functionalized tetracenes R–Tc with two packing motifs: “slip-stack” packing in R = TES, TMS, and tBu and “gamma” packing in R = TBDMS to determine the effects of morphology on SF as well as on photodegradation using a combination of temperature and magnetic field dependent spectroscopy, kinetic modeling, and time-dependent density functional theory. We find that both “slip-stack” and “gamma” packing support SF with high T1 yield at room temperature (up to 191% and 181%, respectively), but “slip-stack” is considerably more advantageous at low temperatures (<150 K). In addition, each packing structure has a distinct emissive relaxation pathway competitive to SF, while the states involved in the SF itself are dark. The “gamma” packing has superior photostability, both in regards to EPO formation and photodimerization. The results indicate that the trade-off between SF efficiency and photostability can be overcome with material design, emphasize the importance of considering both photophysical and photochemical properties, and inform efforts to develop optimal SF materials for (opto)electronic applications.
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- Award ID(s):
- 1956431
- PAR ID:
- 10556085
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 161
- Issue:
- 19
- ISSN:
- 0021-9606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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