An oxorhenium complex bearing a chiral cyclohexane‐1‐olato‐2‐thiolato ligand: Synthesis, stereochemistry, and theoretical study of parity violation vibrational frequency shifts

Abstract

In our effort towards measuring the parity violation energy difference between two enantiomers, a simple chiral oxorhenium complex 5 bearing enantiopure 2-mercaptocyclohexan-1-ol has been prepared as a potential candidate species. Vibrational circular dichroism revealed a chiral environment surrounding the rhenium atom, even though the rhenium is not a stereogenic center itself, and enabled to assign the (1S,2S)-(-) and (1R,2R)-(+) absolute configuration for 5. For both compound 5 and complex 4, previously studied by us and bearing a propane-2-olato-3-thiolato ligand, relativistic calculations predict parity violating vibrational frequency differences of a few hundreds of millihertz, above the expected sensitivity attainable by a molecular beam Ramsey interferometer that we are constructing.

Possible chemical and physical scenarios towards biological homochirality

“…85 Quantitative calculations of this parityviolating energy difference between enantiomers have been improved during the last four decades, [86][87][88][89][90] to give for example about 10 -12 J/mol for CHFClBr. 91,92 Although groups of Crassous/Darquié in France 78,[93][94][95][96][97][98] and Quack in Switzerland ), the parity violating energy difference strongly increases with increasing nuclear charge with a commonly accepted Z 5 scaling law, thus chiral heavy metal complexes might be favourable candidates for future observation of PV effects in chiral molecules. 94,96 Other types of experiments have been proposed to measure PV effects, such as nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), microwave (MW) or Mössbauer spectroscopy.…”

Absolute Configurations of Synthetic Molecular Scaffolds from Vibrational CD Spectroscopy

“…Chiral rhenium complexes such as 98 142,143 have been of interest in studies on parity violations. Paramagnetic compounds usually feature a strong intensity enhancement of VCD spectra that may exceed two orders of magnitude.…”

“…Studies on luminescent transition metal complexes such as 96 − or 97 benefited from the additional structural insights obtained from VCD spectroscopy as well. Chiral rhenium complexes such as 98 , have been of interest in studies on parity violations.…”

A new experiment to test parity symmetry in cold chiral molecules using vibrational spectroscopy

“…We have already worked with theoretical and experimental chemists to find the best chiral species for measuring the PV energy difference. This led to the successful synthesis of solid oxorhenium organo-metallic compounds that have vibrational transitions around 30 THz and PV frequency shifts as large as ~1 Hz (see [5,[18][19][20][21] and references therein), up to 1000 times larger than in CHFClBr. Several other tracks are currently being followed and other molecules are being prepared.…”