Chirality transfer observed in Raman optical activity spectra.

Area of Science:

• Spectroscopy
• Chiroptical phenomena
• Molecular interactions

Background:

• Chirality transfer, or induced chirality, appears as new spectral bands when chiral and achiral molecules interact.
• Recent observations in Raman optical activity (ROA) spectroscopy of achiral solvent bands were attributed to the ECD-Raman (eCP-Raman) effect.

Purpose of the Study:

• To provide an unambiguous demonstration of chirality transfer in ROA spectra.
• To investigate the molecular interactions responsible for chirality transfer in specific systems.

Main Methods:

• ROA spectroscopy was used to analyze mixtures of achiral benzonitrile with enantiomers of chiral alcohols and amines.
• Spectroscopic measurements were repeated to ensure reproducibility.
• Computational methods were employed to analyze intermolecular interactions.

Main Results:

• A distinct v(CN) vibration band at approximately 2230 cm^-1 was observed in the ROA spectra of the mixtures.
• Calculations identified the formation of hydrogen bonds (CN···HO or CN···HNH) and π-interactions (π···π or CH···π).
• The strength of these molecular interactions directly correlated with the prominence of the ROA chirality transfer effect.

Conclusions:

• This study presents a clear example of chirality transfer in ROA spectroscopy.
• Intermolecular interactions, specifically hydrogen bonding and π-interactions, are crucial for observing this phenomenon.
• The findings highlight the importance of interaction strength in the manifestation of ROA chirality transfer.