Dynamic Control and Amplification of Molecular Chirality by Circular Polarized Light

Abstract

The enantiomers of a racemic photoresponsive material represent two distinct states that can be modulated with irradiation at a single wavelength by changing the handedness of the light. Dynamic control over molecular chirality was obtained by the interconversion of enantiomers of helically shaped molecules with either left or right circular polarized light (CPL). Photoresolution of the bistable compound as a dopant in a nematic liquid crystalline phase by CPL irradiation led to a chiral mesoscopic phase. The chiral information inherent to CPL is therefore transmitted to the bistable molecule, followed by amplification and macroscopic expression of the chirality.

Induction and control of supramolecular chirality by light in self-assembled helical nanostructures

“…It has been speculated that this slight chiral bias might have been amplified via autocatalytic reactions or crystallization processes during the evolutionary process 5 , resulting in homochirality. Amplification of the chiral information and macroscopic expression of chirality has been observed with liquid crystals, where the excess enantiomer generated by CPL acts as a chiral dopant and induces a chiral liquid crystalline phase [6][7][8] . Chiral information in CPL could be also transferred to helical polymers and expressed at a secondary structure level, as the handedness of the helix was controlled by the direction of CPL [9][10][11] .…”

Stirring competes with chemical induction in chiral selection of soft matter aggregates

“…For instance, the latter permits the interconversion of enantiomers in a racemic photoresponsive material 13 , or provides a way for chiral induction on achiral azobenzene-based liquid crystalline polymer films 14,15 and, more recently, has rendered possible a strategy for chiral induction on domains of achiral bent-shape dimers 16 . In a different context, another procedure consists in using unpolarized light in the presence of a coaxial magnetic field 17 .…”

In control of switching, motion, and organization

“…Photochemical switching of LC phases using chiral photochromic guest molecules offers an alternative to current methods of addressing display materials [22]. Using a related helical-shaped photobistable alkene 2, switching between enantiomers at a single wavelength of light could also be accomplished, and the slight stereochemical bias that was found can be amplified in a liquid crystal film [23]. The switching process is shown in Scheme 2.…”