Effects of solvent molecules on hemi-bonded (CH3SH)2+: infrared absorption of [(CH3SH)2–X]+ with X = H2O, (CH3)2CO, or NH3 and (CH3SH)n+ (n = 3–6). Issue 29 (10th July 2019)

• Record Type: Journal Article
• Authors: Xie, Min; Tsai, Huei-Ru; Fujii, Asuka; Lee, Yuan-Pern
• Is Part Of: Physical chemistry chemical physics. Volume 21:Issue 29(2019)
• Page Start: 16055
• Page End: 16063
• Publication Date: 2019-07-10
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c9cp03158h
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The (3e-2c)-bonded (CH3 SH)2 + structure is preserved when H2 O, (CH3 )2 CO, or CH3 SH binds, but becomes broken by NH3 because of proton transfer. Abstract : Three-electron two-center (3e-2c) hemi-bonds play important roles in the oxidation and electron transport of proteins and are implicated to be involved in some neurodegenerative diseases. Our previous investigations on infrared (IR) spectra of (CH3 SH)2 + using vacuum-ultraviolet photoionization, infrared dissociation, and time-of-flight detection have shown that (CH3 SH)2 + is (3e-2c)-bonded. To investigate the influence of the solvent molecules on the (3e-2c)-bonded (CH3 SH)2 + in a supersonic jet, we added H2 O or (CH3 )2 CO or NH3 or (CH3 SH) n ( n = 1–4) to (CH3 SH)2 + and investigated their IR action spectra. The (3e-2c)-bonded (CH3 SH)2 + ion core was maintained when a molecule of H2 O or (CH3 )2 CO or CH3 SH binds, indicating that the ion core is more stable than the hydrogen bond, whereas the (3e-2c)-bond became broken by a NH3 molecule because the proton transfer led to a more stable hydrogen-bonded structure. The spectral features of the SH-stretching modes of (CH3 SH) n + ( n = 3–6) indicate that the (3e-2c)-bonded (CH3 SH)2 + ion core is maintained and the first two additional CH3 SH are H-bonded to the free SH groups of the ion core. For larger clusters with n = 5 and 6, the additional solvent molecules likely bind to the first solvation shell. These results show also that the (3e-2c)-bonded S∴S structure is more stable than the S∴O and S∴N structures in [(CH3 SH)2 –X] + with X = H2 O or (CH3 )2 CO or CH3 SH or NH3 .