Identification and Photochemistry of the Mercaptomethyl Radical

Xin Shao; Zhuang Wu; Lina Wang; Guntram Rauhut; Xiaoqing Zeng

doi:10.1021/acs.jpclett.3c02526

Identification and Photochemistry of the Mercaptomethyl Radical

J Phys Chem Lett. 2023 Nov 23;14(46):10450-10456. doi: 10.1021/acs.jpclett.3c02526. Epub 2023 Nov 14.

Authors

Xin Shao¹, Zhuang Wu¹, Lina Wang¹, Guntram Rauhut², Xiaoqing Zeng¹

Affiliations

¹ Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, China.
² Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.

PMID: 37962268
DOI: 10.1021/acs.jpclett.3c02526

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).