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Resistance to Unwanted Photo-Oxidation of Multi-Acene Molecules.
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2020-09-07 , DOI: 10.1021/acs.joc.0c01890
Yu Yan 1 , Zachary A Lamport 2 , Ioannis Kymissis 2 , Samuel W Thomas 1
Affiliation  

Although long acenes remain a key class of π-conjugated molecules for numerous applications, photoinduced oxidation upon exposure of the acene to light, often through sensitization of 1O2, is an important reaction requiring mitigation for most applications. In response to this ongoing challenge, this paper presents a series of four new diarylethynyl-substituted long acenes—three tetracenes and one anthradithiophene—in which the arylene pendants are either benzene, naphthalene, or anthracene. UV/vis and fluorescence spectroscopy reveals that the anthracene-substituted derivatives fluoresce poorly (Φ < 0.01). Although all four long acenes react with 1O2 at expected rates when an external photosensitizer is included and show the expected changes in fluorescence to accompany these reactions, the anthracene-substituted derivatives resist direct photoinduced oxidation. Through a combination of mechanistic experiments, we conclude that rapid nonradiative decay of the anthracene-substituted derivatives, perhaps because of inter-arene torsions that emerge in theoretical geometry optimizations, makes these compounds poor photosensitizers for 1O2 or other reactive oxygen species. This discovery opens new design possibilities for extended acene structures with improved photochemical stability.

中文翻译:

抵抗多并苯分子有害的光氧化。

尽管长并苯仍然是许多应用中的一类重要的π共轭分子,但通常在1 O 2的敏化作用下,将并苯暴露在光下后,光诱导的氧化是重要的反应,在大多数应用中需要缓解。为了应对这一持续的挑战,本文提出了一系列四个新的被二芳基乙炔基取代的长乙炔-三个并四烯和一个蒽噻吩-其中亚芳基侧基为苯,萘或蒽。紫外/可见和荧光光谱显示蒽取代的衍生物发荧光差(Φ<0.01)。尽管所有四个长并苯并发1 O 2当包含外部光敏剂并显示预期的荧光变化以伴随这些反应时,蒽取代的衍生物会以预期的速率发生反应,蒽取代的衍生物可以抵抗直接的光诱导氧化。通过机理实验的结合,我们得出结论,蒽取代的衍生物的快速非辐射衰变,可能是由于理论几何优化中出现的芳烃间扭转,使得这些化合物对1 O 2或其他活性氧种类而言不适合用作光敏剂。该发现为具有改进的光化学稳定性的扩展并苯结构开辟了新的设计可能性。
更新日期:2020-10-02
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