  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.
