Finite Enantiomeric Excess Nucleated in an Achiral Banana Mesogen by Chiral Alignment Surfaces

Abstract

Chirale Polyimidoberflächen führen zu endlicher Enantioselektivität in der B4‐Phase achiraler bananenförmiger Mesogen‐Moleküle (siehe Mikroskopiebild). Ein ee‐Wert von 10 % wurde mithilfe geriebener chiraler Polyimidoberflächen erzielt. Diese Technik weist den Weg zu neuen Möglichkeiten, die Chiralität in chemischen und biologischen Systemen einzustellen.

Chiral Superstructure Mesophases of Achiral Bent‐Shaped Molecules – Hierarchical Chirality Amplification and Physical Properties

“…Using chiral surfaces was also considered as another option. Shiromo et al successfully obtained a statistically imbalance state in the CD signals from P‐14‐OPIMB using rubbed surfaces of a polyimide with chiral side chains (Nissan Chemical) . In this case, enantiomeric excess ( ee ) was estimated to be 10%.…”

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

“…However, the system is not necessarily racemic because an imbalance of chirality can be produced by an external chiral stimulus. At least two methods have been elucidated for this: 1) a small amount of chiral dopant is effective in inducing almost 100 % ee ,5 and 2) a chiral surface has been successfully used to induce a finite ee 6. Herein we demonstrate another method that does not involve chiral molecular species.…”

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

“…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.…”

“…The obtained excess value of one of the two chiral domains was 10% in the cells with rubbed chiral polyimide surfaces. 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.…”