Thioetherification Inducing Efficient Excited Triplet State and Singlet Oxygen Generation: Heavy Atom-Free BODIPY Photosensitizer Based on the S1(n,π*) State,The Journal of Physical Chemistry C

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Thioetherification Inducing Efficient Excited Triplet State and Singlet Oxygen Generation: Heavy Atom-Free BODIPY Photosensitizer Based on the S1(n,π*) State
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2021-03-03 , DOI: 10.1021/acs.jpcc.1c00001
Wenbin Hu ₁ , Xian-Fu Zhang _{2,

3} , Mingyu Liu ₁

Affiliation

We have examined the ability of the newly synthesized thioalkyl and thiophenyl (SR) BODIPYs to generate the excited triplet state (T₁) using the laser flash photolysis technique. Compared to the unsubstituted BODIPY parent, SR BODIPYs are much more efficient in generating T₁. We have also determined the capability of the SR BODIPYs to yield singlet oxygen O₂(¹Δ_g) using two methods: (1) measuring the steady state and time-resolved NIR phosphorescence that peaked at 1270 nm; (2) recording DPBF decomposition caused by the reaction with singlet oxygen. The results show that both thioalkyl and thiophenyl very remarkably increase the quantum yield of singlet oxygen formation up to 0.83 from 0.10. To understand the mechanism, we have studied the related photophysics using steady state and time-resolved fluorescence and UV–vis absorption, as well as quantum chemical calculations based on Density Functional Theory. Both the thioalkyl and thiophenyl remarkably decrease the quantum yield of fluorescence and shorten the fluorescence lifetime of BODIPYs, they also cause the occurrence of a new S₁(n,π*) with a slightly lower energy than S₁(π,π*). Since intersystem crossing (ISC) from S₁(n,π*) to T₁(π,π*) is symmetrically allowed, while ISC from S₁(π,π*) to T₁(π,π*) is symmetrically forbidden, this explains why SR presence renders BODIPY efficient photosensitizer for excited triplet state and singlet oxygen generation. SR induced efficient T₁ formation is different from the cases of carbonyl (C═O) or thiocarbonyl (C═S). This finding provides a new method to get efficient heavy atom free photosensitizers, which is important in developing new generation photosensitizers for photodynamic therapy, photochemical up conversion of near IR sunlight in solar cell, and photoredox catalysis.

中文翻译：

硫醚化诱导有效的激发三重态和单态氧生成：基于S ₁（n，π*）状态的重原子无氧BODIPY光敏剂

我们已经检查了新合成的硫代烷基和硫代苯基（SR）BODIPYs使用激光闪光光解技术产生激发三重态（T ₁）的能力。与未取代的BODIPY亲本相比，SR BODIPY在生成T _1时效率更高。我们还确定了SR BODIPYs的能力，以产生单重态氧Ô ₂（¹ Δ_克）使用两种方法：（1）测量在1270 nm达到峰值的稳态和时间分辨NIR磷光；（2）记录由单线态氧反应引起的DPBF分解。结果表明，硫代烷基和硫代苯基都非常显着地提高了单线态氧形成的量子产率，从0.10提高到0.83。为了了解这种机理，我们研究了使用稳态和时间分辨的荧光和UV-vis吸收的相关光物理，以及基于密度泛函理论的量子化学计算。硫代烷基和硫代苯基均显着降低荧光的量子产率并缩短BODIPYs的荧光寿命，它们还引起新的S ₁（n，π*）的出现，其能量略低于S _1。（π，π*）。由于对称地允许从S ₁（n，π*）到T ₁（π，π*）的系统间交叉（ISC），而对称地从S ₁（π，π*）到T ₁（π，π*）的ISC禁止，这解释了为什么SR存在使BODIPY有效的光敏剂用于激发三重态和单重态氧的产生。SR诱导的有效T ₁形成与羰基（C = O）或硫代羰基（C = S）的情况不同。这一发现为获得有效的无重原子光敏剂提供了一种新方法，这对开发用于光动力疗法，太阳能电池中近红外太阳光的光化学上转换以及光氧化还原催化作用的新一代光敏剂具有重要意义。

更新日期：2021-03-11

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