Ghosh Sujit Kumar, Chatterjee Shreya, Boruah Paras Pratim, Mandal Satyajit, Da Silva José P, Srinivasan Varadharajan, Ramamurthy Vaidhyanathan
Department of Chemistry, University of Miami, Coral Gables, FL, 33146, USA.
Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal, MP, 462066, India.
Photochem Photobiol Sci. 2024 Nov;23(11):2057-2073. doi: 10.1007/s43630-024-00651-1. Epub 2024 Nov 4.
Herein, we establish the release of aliphatic acids in water upon excitation of 7-diethylaminothio-4-coumarinyl derivatives encapsulated within the organic host octa acid (OA). The 7-diethylaminothio-4-coumarinyl skeleton, employed here as the trigger, photoreleases caged molecules from the excited triplet state, in contrast to its carbonyl analogue, where the same reaction is known to occur from the excited singlet state. Encapsulation in OA solubilizes molecules in water that are otherwise water-insoluble, and retains the used trigger within itself following the release of the aliphatic acid. Such supramolecular characteristics usher in new features to the photorelease methodology. The thiocarbonyl chromophore extends the absorption of coumarinyl trigger to visible range while enhancing the intersystem crossing (ISC) to the triplet state, making it the reactive state. Despite the non-polar environment within the OA capsules the photocleavage occurs in a heterolytic fashion to release the conjugate base and the used trigger as triplet carbocation in an adiabatic process. Interestingly, the triplet carbocation crosses to the ground singlet surface (closed shell singlet carbocation) with the help of water molecules, possibly aided by C = S chromophore. Utilizing the known excited state dynamics of related thiocoumarinyl and coumarinyl systems, we have identified a few of the important mechanistic features of the photorelease process of 7-diethylaminothio-4-coumarinyl derivatives. Ultrafast excited state dynamic studies and quantum chemical calculations planned should help us better understand the photorelease process so as to effectively exploit the proposed system for potential applications.
在此，我们证实了封装在有机主体八酸（OA）中的7-二乙氨基硫代-4-香豆素基衍生物受激发后会在水中释放脂肪酸。本文采用的7-二乙氨基硫代-4-香豆素基骨架作为触发基团，能从激发三重态光释放笼形分子，这与其羰基类似物不同，后者已知是从激发单重态发生相同反应。封装在OA中可使原本不溶于水的分子在水中溶解，并在脂肪酸释放后将用过的触发基团保留在其自身内部。这种超分子特性为光释放方法带来了新特性。硫羰基发色团将香豆素基触发基团的吸收扩展到可见光范围，同时增强了系间窜越（ISC）至三重态，使其成为反应态。尽管OA胶囊内部为非极性环境，但光裂解以异裂方式发生，在绝热过程中释放共轭碱和用过的触发基团作为三重态碳正离子。有趣的是，三重态碳正离子在水分子的帮助下，可能借助C = S发色团，跃迁到基态单重表面（闭壳单重碳正离子）。利用相关硫代香豆素基和香豆素基体系已知的激发态动力学，我们确定了7-二乙氨基硫代-4-香豆素基衍生物光释放过程的一些重要机理特征。计划进行的超快激发态动力学研究和量子化学计算应有助于我们更好地理解光释放过程，从而有效地开发所提出的体系以用于潜在应用。
