SH···S H-Bonded Ethanethiol Clusters in Cold Argon and Nitrogen Matrices: An IR Spectroscopic Study

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Hydrogen bonding plays a crucial role in molecular interactions and material properties.
• Understanding the conformational behavior of small molecular clusters is essential for various chemical and biological processes.

Purpose of the Study:

• To experimentally characterize the S−H···S hydrogen-bonded ethanethiol (EtSH) dimer and trimer conformers.
• To elucidate the relationship between molecular conformation, hydrogen bond strength, and stability in EtSH clusters.
• To compare the interaction dynamics in EtSH clusters with those in hydrogen sulfide (H2S) clusters.

Main Methods:

• Matrix isolation spectroscopy in argon and nitrogen matrices.
• Analysis of the S−H stretching frequency (${\nu }_{S-H}$) region.
• Quantum chemical calculations (ωB97X-D/aug-cc-pV(D + d)Z) for conformational analysis and frequency prediction.

Main Results:

• Over 20 spectral bands were observed for EtSH dimer and trimer in both matrices, with significant ${\nu }_{S-H}$ spectral shifts.
• Calculations predicted 24 dimer and 45 trimer conformers; 16 dimers and 9 trimers were experimentally identified.
• Most stable conformers exhibited weaker, longer S−H···S bonds, while less stable ones had stronger, shorter bonds.
• EtSH clusters displayed a greater contribution of dispersion interactions compared to H2S clusters.

Conclusions:

• The conformational landscape of EtSH dimer and trimer is complex, with relative stabilities showing minor variations.
• The observed spectral shifts correlate with calculated frequencies, validating the theoretical models.
• Dispersion forces play a significant role in stabilizing ethanethiol clusters, distinguishing them from simpler hydrogen sulfide clusters.