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Updated: Jul 11, 2025

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Identification and Photochemistry of the Mercaptomethyl Radical
Xin Shao1, Zhuang Wu1, Lina Wang1
1Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, China.
Abstract:
The mercaptomethyl radical (·CH2SH) is a higher-energy isomer of the methylthio radical (CH3S·) that has been proposed as an important intermediate in atmospheric and interstellar sulfur chemistry. Herein, we report the spectroscopic identification of ·CH2SH during the UV (365 nm) photolysis of CH3S· in a solid Ar-matrix at 10 K. Upon subsequent irradiation at 266 nm, the dehydrogenation of ·CH2SH to yield CS via the intermediacy of the elusive thioformyl radical (HCS·) has also been observed. The characterization of ·CH2SH and HCS· with matrix-isolation IR and UV-vis spectroscopy is supported by 13C-isotope labeling and quantum chemical calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level using configuration-selective vibrational configuration interaction theory (VCI). The disclosed photochemistry of ·CH2SH provides new insight into understanding the chemical evolution of organosulfur molecules in the interstellar medium (ISM).
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