Laser-operated chiral molecular switch: quantum simulations for the controlled transformation between achiral and chiral atropisomers

Abstract

We report quantum dynamical simulations for the laser controlled isomerization of 1-(2-cis-fluoroethenyl)-2-fluorobenzene based on one-dimensional electronic ground and excited state potentials obtained from (TD)DFT calculations. 1-(2-cis-fluoroethenyl)-2-fluorobenzene supports two chiral and one achiral atropisomers, the latter being the most stable isomer at room temperature. Using a linearly polarized IR laser pulse the molecule is excited to an internal rotation around its chiral axis, i.e. around the C-C single bond between phenyl ring and ethenyl group, changing the molecular chirality. A second linearly polarized laser pulse stops the torsion to prepare the desired enantiomeric form of the molecule. This laser control allows the selective switching between the achiral and either the left- or right-handed form of the molecule. Once the chirality is "switched on" linearly polarized UV laser pulses allow the selective change of the chirality using the electronic excited state as intermediate state.

A combined experimental and theoretical study on realizing and using laser controlled torsion of molecules

“…We will now discuss some perspectives of the demonstrated laser control of torsion. For one thing, we suggest a time-resolved study of de-racemization [34,35,36,37,38], where one enantiomer is steered into its mirror form. To do this we break the inversion symmetry of the C-C bond axis by orienting each molecule.…”

Quantum chemical and dynamical approaches to intra and intermolecular kinetics: The CnH2nO (n = 1, 2, 3) molecules

“…No direct conversion channel with only one transition state exists between the P and M enantiomers of propylene oxide. We have carried out an extensive study on the various isomerization paths and chirality exchange paths, which are schematically represented in Figures 4 and 5, respectively, providing ground for investigations of chiral exchange or switching mechanism reactions, for which considerable progress has been recorded in recent times46. More details on the isomerization and chirality changing mechanisms will be published in future47.…”

Nuclear Spin Selective Torsional States: Implications of Molecular Symmetry

“…This goal is motivated by previous demonstrations of quantum control of molecular torsions for various purposes, e.g. energy transfer [77]; enhancement of transient absorption spectroscopy [73]; the ignition of molecular motors [55,64,78]; and the preparation of pure enantiomers out of racemic mixtures [59,61,63,65,73,79]. (i) Their structures at the minima of the potential energy surface of the electronic ground state ("minimum structures") have a C 2 symmetry axis.…”