Infrared Spectroscopy of Ethanethiol Monomers and Dimers at MP2 Level: Characterizing the Dimer Formation and Hydrogen Bond

• Published in: Journal of computational chemistry Vol. 46; no. 1; pp. e27540 - n/a
• Main Authors: Brito, Airan F. S., Aquino, Adelia J. A., Santos Politi, José Roberto, Martins, João B. L.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 05.01.2025; Wiley Subscription Services, Inc
• Subjects: astrochemistry; Dimers; ethanethiol dimer; Ethanol; Hydrogen bonds; Interstellar chemistry; Interstellar matter; Isomers; local modes decomposition; Monomers; Organosulfur compounds; Spectrum analysis; sulfur center hydrogen bond; S–H⋅⋅⋅S interaction; Vibration mode; astrochemistry; S–H⋅⋅⋅S interaction; ethanethiol dimer; sulfur center hydrogen bond; local modes decomposition
• ISSN: 0192-8651; 1096-987X; 1096-987X
• DOI: 10.1002/jcc.27540

ABSTRACT Ethanethiol, also known as ethyl mercaptan, is an organosulfur compound that appears as a colorless liquid with a distinctive odor. It has been detected in the interstellar medium, and its self‐association has been the subject of a few known experimental studies, where the SH vibrational mode was used. However, unlike the analogous ethanol dimer, the ethanethiol dimer has not been thoroughly explored theoretically. In this study, ethanethiol and dimers were investigated using the MP2 method with various basis sets to determine the properties and stability of these structures. For the monomer, both trans and gauche structures were computed, with the gauche conformer being more stable, consistent with the available data in the literature. Local mode decomposition analysis of monomers showed that the CH2 rocking mode, associated with the CSH bending, is present only for the gauche isomer aligning with the experimental assignments. Furthermore, eight stable dimer configurations were identified and categorized into three groups: trans–trans, gauche–gauche, and trans–gauche isomers. Among these, the trans–gauche isomer was found to be the most stable. Dispersion is the dominant term for the ethanethiol dimer. The local mode decomposition revealed that the CH2 rocking mode, associated with the CSH bending, appears only for the gauche isomer in accordance with the experimental assignments. The most stable dimer is the trans(right)–gauche(left) structure. The HOMO orbital is located on the donor monomer, and the LUMO orbital is located on the acceptor monomer, supporting the largest redshift of 33 cm−1 obtained for the gauche isomer. The configuration shows the S–H donor directed to the S acceptor with the NCI isosurface. The LUMO orbital also shows the S⋅⋅⋅S interatomic distance. Dispersion is the dominant term in this dimer, while electrostatic interactions comprise 83% of dispersion. ELF values at the critical point of S–H⋅⋅⋅S interaction describe an almost linear form of the interaction energy.