Circular‐Polarization‐Induced Enantiomeric Excess in Liquid Crystals of an Achiral, Bent‐Shaped Mesogen

Abstract

Imperative irradiation: A large enantiomeric excess in a liquid‐crystal phase can be induced by circularly polarized light (CPL) as an external stimulus, and an imbalance in the two chiral domains becomes remarkable in the BX phase (see pictures), which is similar to the B4 phase made up by classical bent‐core mesogens.

Intrinsic chiral domains enantioselectively segregated from twisted nematic cells of bent‐core mesogens

“…20 The second method (circularly polarized light irradiation) brings about a large imbalance in the two chiral domains of the Bx phase, which is similar to the B4 phase, in bent-core dimer with azo linkages at both side wings. 21 The last method, which was more recently reported, also displays a preferential formation of chiral conglomerate with one handedness in the Bx phase of oxadiazole-based bent-core molecule, which exhibits the liquid crystal (LC) polymorphism including both the calamitic and banana phases, under twisted nematic (TN) cell geometries. 22 This method is based on conventional LC alignment technique and expected to be simple and most efficient for lifting degeneracy.…”

“…When spontaneous symmetry breaking occurs, randomly uncontrollable chiral domains with (þ) and (À) chirality are inevitably formed, i.e., from the energetic point of view, these two chiral domains can exist with an equal probability. 19 Recently, in B4 or unidentified analogous B4 phases, several methods for breaking these inevitable degeneracy were proposed and demonstrated; uses of (1) chiral surfaces, 20 (2) circularly polarized light, 21 and (3) extrinsic chiral structure. 22 The first technique shows that substrate surfaces with polyimide layers possessing chiral side chains induce an imbalance between the two chiral domains.…”

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

“…Supramolecular chirality has been generally induced by the self-assembly of homochiral molecules or a mixture of chiral and achiral molecules, where the molecular chirality is transferred (and amplified as well in case of the mixture) to the handedness of the self-assembled helical structure [12][13][14][15] . Only a few papers have described generation of supramolecular chirality by irradiation of azobenzene-containing achiral molecules with CPL, presumably through alignment of the azobenzene chromophores following the direction of CPL [16][17][18] .…”

Light‐Driven Supramolecular Chirality in Propeller‐Like Hydrogen‐Bonded Complexes That Show Columnar Mesomorphism

“…[8] The use of circularly polarized light (CPL) as the irradiation source has led to enantiomeric excess values in two chiral domains in the Bx phase of bent-core molecules. [9] Moreover, supramolecular chirality photoinduced by CPL has been reported in azopolymers [10] and in main-chain polymeric liquid-crystal systems doped with azobenzene-containing W-shaped molecules. [11] However, attempts to induce supramolecular chirality in columnar mesophases formed by azobenzene-containing mesogens have not been described to date.…”