Dutta Abhijit, Ghosh Sujit Kumar, Mandal Satyajit, Srinivasan Varadharajan, Ramamurthy Vaidhyanathan, Sen Pratik
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016 Uttar Pradesh, India.
Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States.
J Phys Chem A. 2024 Aug 22;128(33):6853-6863. doi: 10.1021/acs.jpca.4c03139. Epub 2024 Aug 13.
The photochemistry and photophysics of thiocarbonyl compounds, analogues of carbonyl compounds with sulfur, have long been overshadowed by their counterparts. However, recent interest in visible light reactions has reignited attention toward these compounds due to their unique excited-state properties. This study delves into the ultrafast dynamics of 7-diethylaminothiocoumarin (TC1), a close analogue of the well-known probe molecule coumarin 1 (C1), to estimate intersystem crossing rates, understand the mechanisms of fluorescence and phosphorescence, and evaluate TC1's potential as a solvation dynamics probe. Enclosing TC1 within an organic capsule indicates its potential applications, even in aqueous environments. Ultrafast studies reveal a dominant subpicosecond intersystem crossing process, indicating the importance of upper excited singlet and triplet states in the molecule's photochemistry. The distinct fluorescence and phosphorescence origins, along with the presence of closely spaced singlet excited states, support the observed efficient intersystem crossing. The sulfur atom alters the excited-state behavior, shedding light on reactive triplet states and paving the way for further investigations.
硫羰基化合物是羰基化合物的含硫类似物，其光化学和光物理性质长期以来一直被其羰基对应物所掩盖。然而，由于其独特的激发态性质，近期对可见光反应的兴趣重新点燃了人们对这些化合物的关注。本研究深入探讨了7-二乙氨基硫代香豆素（TC1）的超快动力学，它是著名探针分子香豆素1（C1）的紧密类似物，以估计系间窜越速率，理解荧光和磷光的机制，并评估TC1作为溶剂化动力学探针的潜力。将TC1封装在有机胶囊中表明了其潜在应用，甚至在水性环境中也是如此。超快研究揭示了一个占主导地位的亚皮秒系间窜越过程，表明分子光化学中较高激发单重态和三重态的重要性。独特的荧光和磷光起源，以及紧密间隔的单重激发态的存在，支持了所观察到的高效系间窜越。硫原子改变了激发态行为，为反应性三重态提供了线索，并为进一步研究铺平了道路。
