A chiral rhenium complex with predicted high parity violation effects: synthesis, stereochemical characterization by VCD spectroscopy and quantum chemical calculations

TL;DR

This study synthesizes chiral oxorhenium(VII) complexes, characterizes their stereochemistry via VCD spectroscopy, and predicts that their vibrational parity violation effects are detectable with high-resolution spectroscopy, aiding fundamental physics tests.

Contribution

It introduces new chiral rhenium complexes and combines experimental VCD with quantum calculations to predict observable parity violation effects in these molecules.

Findings

VCD spectra confirmed chiral environment around Re=O

Two conformers of similar stability identified

Parity violation vibrational shifts predicted above detection threshold

Abstract

With their rich electronic, vibrational, rotational and hyperfine structure, molecular systems have the potential to play a decisive role in precision tests of fundamental physics. For example, electroweak nuclear interactions should cause small energy differences between the two enantiomers of chiral molecules, a signature of parity symmetry breaking. Enantioenriched oxorhenium(VII) complexes S-(-)- and R-(+)-3 bearing a chiral 2-methyl-1-thio-propanol ligand have been prepared as potential candidates for probing molecular parity violation effects via high resolution laser spectroscopy of the Re=O stretching. Although the rhenium atom is not a stereogenic centre in itself, experimental vibrational circular dichroism (VCD) spectra revealed a surrounding chiral environment, evidenced by the Re=O bond stretching mode signal. The calculated VCD spectrum of the R enantiomer confirmed the position of the sulfur atom cis to the methyl, as observed in the solid-state X-ray crystallographic structure, and showed the presence of two conformers of comparable stability. Relativistic quantum chemistry calculations indicate that the vibrational shift between enantiomers due to parity violation is above the target sensitivity of an ultra-high resolution infrared spectroscopy experiment under active preparation.