Electroweak interactions in chiral molecules: two-component density functional theory study of vibrational frequency shifts in polyhalomethanes

Abstract

In this paper, a two-component density functional theory study of parity violation-induced vibrational frequency shifts in chiral polyhalomethanes is reported and the prospects to detect in these compounds, for the first time, signals of parity violation in molecular systems are discussed. The recent synthesis of enantiomerically enriched CHClFI has renewed interest in examining electroweak corrections for this class of compounds. Utilizing a (quasi-relativistic) two-component zeroth-order regular approximation approach to molecular parity violation, together with density functional theory, the parity violation-induced relative vibrational frequency splittings Δ ν_pv/ν between the C–F stretching fundamental of polyhalomethane enantiomers are computed. The relative splitting in CHClFI is raised compared with CHBrClF, for which upper bounds were determined experimentally. To facilitate measurement, molecules possessing more pronounced relative splittings are desirable. Therefore, the chiral methane derivative CHAtFI is considered, which exhibits a significantly larger electroweak contribution that induces a vibrational frequency splitting on the order of the experimental resolution previously reported for CHBrClF. Employing compounds containing heavy nuclei such as astatine may thus be necessary with present detection methods.

Keywords:

• Molecular parity violation
• Electroweak quantum chemistry
• Polyhalomethanes
• Vibrational frequency shifts
• Zeroth-order regular approximation

Acknowledgements

Discussions with Jürgen Stohner and Sophie Nahrwold are gratefully acknowledged. This work was supported by the Volkswagen Foundation. We also acknowledge the HLRN and the CSC Frankfurt for access to their computing facilities.