Observation of polar order and thermochromic behaviour in a chiral bent-core system exhibiting exotic mesophases due to superstructural frustration

Abstract

A new approach accompanied by superstructural frustration is reported. By attaching a cholesterol moiety directly to the central bent-core system it displayed exotic BPIII, BPII/I, Ncyb*, TGBA, SmAPA, SmA and SmX phases as shown by X-ray scattering results. While higher homologues of the series exhibited spontaneous formation of polar order (Ps ∼ 61 nC cm-2) upon applied voltage, the lower homologues showed thermochromic behaviour which can also be trapped via temperature quenching.

Chiral Bent‐Shaped Molecules Exhibiting Unusually Wide Range of Blue Liquid‐Crystalline Phases and Multistimuli‐Responsive Behavior

“…Othert han these major differences, the two molecules had differencesi no ther bond angles and torsion angles of AD FT study was performed on compound 1-4 (as ar epresentativec ase) and an analogous compound with am ethyl core reported earlier. [47] It was found that the dipole moment along the y direction( Figure S40 and Ta bles S6 and S7 in the Supporting Information) was much larger (m y = 2.55 D) in compound 1-4 than that in the previously reported molecule (m y = 1.272 D), although the dipole moments along the other two directions (x and z)r emained similari nb oth compounds. This observation implies that the introduction of the ÀCl moiety in the kink direction of the molecule (Figure 2a)e lectronically affects nucleation of the usual mesophases (e.g.,n ematic or Sm) and stabilizes the frustrated BPs.…”

“…[43][44][45] Therefore, the salicylideneaniline and cholesterol units play an important role in the mechanochromic behavior of this class of compounds. [43][44][45][46] In our previous report, [47] we showedt hat 3-amino-2-methylbenzoica cid (as the central core, [47-49, 52, 53, 55] Figure 1a)b ased smartb ent-core materials exhibited frustrated structures that stabilized BPs for about 2.0 8C and the TGB phase fora bout 31.0 8C. The direct attachment of the cholesterol moiety to the central core, functioning as an arm of the BCLC (Figure 1), promotes rigidness in the molecular architecture, which eventually leads to the realization of different frustrated phases.T he methyl group (ÀCH 3 ), with the + I effect and its bulky size (relative to H), widened the bent angle and supported the stabilization of different phase structures.…”

“…Chiral bent-core molecules with a) a ÀCH 3 moiety at the kink position (previously reported in ref. [47]) and b) a ÀCl moiety at the kink position of the central unit (the moleculed escribedherein). system with the P2 1 space group, with two independent molecules of different conformations (conformations A( C1A to C45A) and B( C1B to C45B)) in the asymmetric unit (Z = 4, Z' = 2).…”

“…In the present study,c ompound 1-10, exhibiting the N cyb *p hase, showedt hermochromic behavior upon cooling the sample. [47,68] The sample melteda tatemperature of 145.4 8Ca nd a yellow liquid was formed ( Figure 10 a). Upon cooling and subsequently holding sample 1-10 at 125.0 8C, the melted yellow sample startedt oc onvert into green at one of the corners (Figure 10 b) because it convertedt ot he N* phase from the yellow liquid.…”

“…In addition, we observe av ariety of phases, such as BPI/II, N*, TGBA, SmA, and an unknown tiltedp hase, SmX, for two homologues (1-12 and 1-14), similart ot hat previously reported. [47] Compounds 1-16 and 1-18 stabilizet he SmX phase enantiotropically.T he phase sequence of all compounds is summarized in Figure S83 in the SupportingI nformationd uring cooling. The presence of the ÀCl moiety in the central core, which is evident from the single-crystals tructure and density functional theory (DFT) analysis,h as allowed more insights regarding stabilization of the frustrated structures in these molecular systems.…”