Dynamic Photoswitching of Helical Inversion in Liquid Crystals Containing Photoresponsive Axially Chiral Dopants

Abstract

Chirality switching is intriguing for the dynamic control of the electronic and optical properties in nanoscale materials. The ability to photochemically switch the chirality in liquid crystals (LCs) is especially attractive given their potential applications in electro-optic displays, optical data storage, and the asymmetric synthesis of organic molecules and polymers. Here, we present a dynamic photoswitching of the helical inversion in chiral nematic LCs (N*-LCs) that contain photoresponsive axially chiral dopants. Novel photoresponsive chiral dithienylethene derivatives bearing two axially chiral binaphthyl moieties are synthesized. The dihedral angle of the binaphthyl rings changes via the photoisomerization between the open and closed forms of the dithienylethene moiety. The N*-LCs induced by the dithienylethene derivatives that are used as chiral dopants exhibit reversible photoswitching behaviors, including a helical inversion in the N*-LC and a phase transition between the N*-LC and the nematic LC. The present compounds are the first chiral dopants that induce a helical inversion in N*-LC via the photoisomerization between open and closed forms of the dithienylethene moiety.

Photoresponsive Cholesteric Liquid Crystals

“…Very recently, a binaphthyl-derived diarylethene dopant was demonstrated exhibiting the handedness inversion behavior when employed as the chiral dopant [81]. The open form of (R)-25 induced a right-handed CLC, while the handedness could be switched to lefthanded upon UV irradiation.…”

Dynamic Figure Eight Chirality: Multifarious Inversions of a Helical Preference Induced by Complexation

“…2a−c Lability in dynamic chiral molecules presents a fascinating challenge regarding how we might induce a preferred sense of dynamic chirality as well as how we could reverse this preference in response to a change in environmental conditions, such as an electrical field, 3 temperature, 4 solvent, 5 or photoirradiation. 6 The addition of a guest can offer a solution to this task, 5g, allowing us to envision more advanced systems in which a helical preference is specifically reversed upon complexation because we can select various guests with different structures in terms of shape, 5g size, 7f and chirality. Here, we report the inversion of a helical preference upon complexation of a dynamic figure eight molecule with a guest molecule through the controlled transmission of point chirality (Scheme 1).…”

“…6a: mp 50.0−52.0°C. 1 H NMR (400 MHz, CDCl 3 , TMS): δ 7.69 (2H, dd, J = 1.6, 7.2 Hz), 7.54 (2H, dd, J = 1 6,. 7.2 Hz), 7.47 (2H, dt, J = 1.6, 7.2 Hz), 7.43 (2H, dt, J = 1.6, 7.2 Hz), 7.25 (4H, d, J = 8.4 Hz), 7.08 (4H, d, J = 8.4 Hz), 3.68 (4H, t, J = 7.6 Hz), 1.53− 1.46 (4H, m), 1.30 (4H, sext, J = 7.2 Hz), 0.89 (6H, t, J = 7.2 Hz) 13.…”

2-Octyl thiophene based three ring mesogens: solid state 13C NMR and XRD investigations

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].0° in the measured temperature range (Table 5). By using the relationship S zz (II)/S zz (T) = P 2 (cosθ), 67 the angle θ between thiophene and phenyl ring is calculated to be 14.…”