Visible‐Light‐Driven Full‐Spectrum Tuning in Cholesteric Liquid Crystals Enabled by Thioarylazopyrazole‐Based Axially Chiral Molecular Switches

ABSTRACT

Cholesteric liquid crystals (CLCs) with structural color reflection are promising for photonic applications, where chiral photoswitches are widely used to dynamically tune supramolecular helices. However, the limited tunability of helical twisting power (HTP) makes it challenging to shift the selective reflection band out of the visible region. Moreover, most reported molecular systems still rely on harmful UV light due to the relatively small π ‐conjugation. Here, three novel thioarylazopyrazole chiral dopants are designed and synthesized, enabling bidirectional photoisomerization driven by visible light with high photoconversion efficiency. By varying the linkage position between the azo group and pyrazole unit, these switches with tunable thermal half‐lives are obtained. When the switch is co‐doped with a photoinsensitive chiral dopant into the liquid crystal E7, the reflection band of the CLC system can be shifted bidirectionally from the UV (340 nm) to the NIR (800 nm) under visible‐light irradiation. Furthermore, by irradiating at selected wavelengths, photostationary states corresponding to the RGB primary colors are precisely achieved. This work introduces a visible‐light‐driven chiral dopant system that shifts the selective reflection band into and out of the visible region for dynamic optical information encryption without relying on high‐energy UV irradiation.