Riyad Yasser M, Naumov Sergej, Hermann Ralf, Brede Ortwin
University of Leipzig, Interdisciplinary Group Time-Resolved Spectroscopy, Permoserstr. 15, D-4303, Leipzig, Germany.
Phys Chem Chem Phys. 2006 Apr 14;8(14):1697-706. doi: 10.1039/b516924k. Epub 2006 Feb 23.
On the bases of picosecond and nanosecond laser flash photolysis with detection by emission and absorption spectroscopy, a quantitative description is given of all deactivation channels of the first excited singlet state of thiophenols ArSH(S(1)) such as fluorescence, intersystem crossing (ISC), chemical dissociation into radicals, and radiation-less internal conversion (IC). For this purpose, the photolysis of thiophenol and its methyl-, methoxy-, and chloro-substituted derivatives was studied in solvents of increasing polarity: 1-chlorobutane, ethanol, and acetonitrile. The fluorescence lifetime of the thiophenols was found to range from some hundreds of picoseconds up to a few nanoseconds, correlating with fluorescence quantum yields between 0.001-0.040, at room temperature. Depending on the substitution pattern of the aromatic ring, the quantum yield of the S-H bond dissociation was found to be between 0.3-0.5, irrespective of the solvent polarity. In laser photolysis, no triplet formation of the investigated compounds could be observed neither by the direct way nor by subsequent sensitization with beta-carotene. As a difference to the total, the radiation-less internal conversion (Phi(IC)>or= 0.5) was found to be the dominating process.
基于皮秒和纳秒激光闪光光解，并通过发射光谱和吸收光谱进行检测，对苯硫酚ArSH的第一激发单重态（S(1)）的所有失活通道进行了定量描述，这些通道包括荧光、系间窜越（ISC）、化学解离成自由基以及无辐射内转换（IC）。为此，在极性递增的溶剂（1-氯丁烷、乙醇和乙腈）中研究了苯硫酚及其甲基、甲氧基和氯取代衍生物的光解。发现苯硫酚的荧光寿命在室温下从几百皮秒到几纳秒不等，与荧光量子产率在0.001 - 0.040之间相关。根据芳环的取代模式，发现S - H键解离的量子产率在0.3 - 0.5之间，与溶剂极性无关。在激光光解中，无论是直接方式还是随后用β-胡萝卜素敏化，均未观察到所研究化合物形成三重态。与总体情况不同的是，发现无辐射内转换（Φ(IC)≥0.5）是主导过程。
