Dataset Information

Efficient Photooxidation of Sulfides with Amidated Alloxazines as Heavy-atom-free Photosensitizers.

ABSTRACT: Photooxidation utilizing visible light, especially with naturally abundant O2 as the oxygen source, has been well-accepted as a sustainable and efficient procedure in organic synthesis. To ensure the intersystem crossing and triplet quantum yield for efficient photosensitization, we prepared amidated alloxazines (AAs) and investigated their photophysical properties and performance as heavy-atom-free triplet photosensitizers and compared with those of flavin (FL) and riboflavin tetraacetate (RFTA). Because of the difference in the framework structure of AAs and FL and the introduction of carbonyl moiety, the absorption of FL at ?450 nm is blue-shifted to ?380 nm and weakened (? = 8.7 × 103 for FL to ?6.8 × 103 M-1 cm-1), but the absorption at ?340 nm is red-shifted to ?350 nm and enhanced by ?50% (from ? = 6.4 × 103 for FL to ?9.9 × 103 M-1 cm-1) in AAs. The intersystem crossing rates from the S1 to T1 are also enhanced in these AAs derivatives, while the fluorescence quantum yield decreases from ?30 to ?7% for FL and AAs, respectively, making the triplet excited state lifetime and the singlet oxygen quantum yield of AAs at least comparable to those of FL and RFTA. We examined the performance of these heave-atom-free chromophores in the photooxidation of sulfides to afford sulfoxides. In accordance with the prolonged triplet excited state lifetime and enhanced triplet quantum yield, 2-5-fold performance enhancements were observed for AAs in the photooxidation of sulfides with respect to FL. We proposed that the key reactive oxygen species of AA-sensitized photooxidation are singlet oxygen and superoxide radical anion based on mechanistic investigations. The research highlights the superior performance of AAs in photocatalysis and would be helpful to rationalize the design of efficient heavy-atom-free organic photocatalysts.

SUBMITTER: Guo H

PROVIDER: S-EPMC7227068 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Efficient Photooxidation of Sulfides with Amidated Alloxazines as Heavy-atom-free Photosensitizers.

Guo Huimin H Xia Hongyu H Ma Xiaolin X Chen Kepeng K Dang Can C Zhao Jianzhang J Dick Bernhard B

ACS omega 20200428 18

Photooxidation utilizing visible light, especially with naturally abundant O<sub>2</sub> as the oxygen source, has been well-accepted as a sustainable and efficient procedure in organic synthesis. To ensure the intersystem crossing and triplet quantum yield for efficient photosensitization, we prepared amidated alloxazines (AAs) and investigated their photophysical properties and performance as heavy-atom-free triplet photosensitizers and compared with those of flavin (FL) and riboflavin tetraac ...[more]

PMID: 32426617

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Project description:Heavy-atom-free sensitizers forming long-living triplet excited states via the spin-orbit charge transfer intersystem crossing (SOCT-ISC) process have recently attracted attention due to their potential to replace costly transition metal complexes in photonic applications. The efficiency of SOCT-ISC in BODIPY donor-acceptor dyads, so far the most thoroughly investigated class of such sensitizers, can be finely tuned by structural modification. However, predicting the triplet state yields and reactive oxygen species (ROS) generation quantum yields for such compounds in a particular solvent is still very challenging due to a lack of established quantitative structure-property relationship (QSPR) models. In this work, the available data on singlet oxygen generation quantum yields (ΦΔ ) for a dataset containing >70 heavy-atom-free BODIPY in three different solvents (toluene, acetonitrile, and tetrahydrofuran) were analyzed. In order to build reliable QSPR model, a series of new BODIPYs were synthesized that bear different electron donating aryl groups in the meso position, their optical and structural properties were studied along with the solvent dependence of singlet oxygen generation, which confirmed the formation of triplet states via the SOCT-ISC mechanism. For the combined dataset of BODIPY structures, a total of more than 5000 quantum-chemical descriptors was calculated including quantum-chemical descriptors using density functional theory (DFT), namely M06-2X functional. QSPR models predicting ΦΔ values were developed using multiple linear regression (MLR), which perform significantly better than other machine learning methods and show sufficient statistical parameters (R=0.88-0.91 and q2 =0.62-0.69) for all three solvents. A small root mean squared error of 8.2 % was obtained for ΦΔ values predicted using MLR model in toluene. As a result, we proved that QSPR and machine learning techniques can be useful for predicting ΦΔ values in different media and virtual screening of new heavy-atom-free BODIPYs with improved photosensitizing ability.

Dataset Information

Efficient Photooxidation of Sulfides with Amidated Alloxazines as Heavy-atom-free Photosensitizers.

Publications

Efficient Photooxidation of Sulfides with Amidated Alloxazines as Heavy-atom-free Photosensitizers.

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