Optical Kerr effect spectroscopy of CS₂ in monocationic and dicationic ionic liquids: insights into the...

Area of Science:

• Physical Chemistry
• Spectroscopy
• Materials Science

Background:

• Ionic liquids (ILs) are tunable solvents with diverse applications.
• Understanding solute-solvent interactions in ILs is crucial for designing new materials.
• Carbon disulfide (CS₂) can serve as a spectroscopic probe for molecular dynamics.

Purpose of the Study:

• To comparatively study the intermolecular dynamics of CS₂ in monocationic and dicationic ionic liquids.
• To investigate the effect of IL structure on CS₂ solvation and confinement.
• To elucidate the role of CS₂ as a probe for intermolecular and interionic interactions in ILs.

Main Methods:

• Optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES) was employed.
• Reduced spectral densities (RSDs) of CS₂ in various ILs were measured as a function of concentration.
• An additivity model was used to isolate the CS₂ contribution to the RSD.

Main Results:

• The intermolecular spectrum of CS₂ in both monocationic and dicationic ILs was lower in frequency and narrower than in neat CS₂.
• CS₂ exhibited a higher frequency intermolecular spectrum in dicationic ILs compared to monocationic ILs.
• This indicates a stiffer potential experienced by CS₂ in dicationic ILs due to greater confinement.

Conclusions:

• Dicationic ionic liquids impose greater confinement on CS₂ molecules than monocationic ILs.
• CS₂ serves as an effective probe for unraveling dilution effects and intermolecular potentials in IL solutions.
• The findings are consistent with molecular dynamics simulations, validating the experimental approach.