Pathway-Dependent Control of Chiral Phases for Higher Performance and Inverted Circularly Polarized Luminescence

Abstract

Chiral luminescent materials have garnered increasing attention for their exceptional ability to emit circularly polarized luminescence (CPL) along with their excellent applications. Here, a cyclohexylidene scaffold was conceptualized as a chiral source for developing higher-performance CPL materials in terms of simultaneously enhanced quantum yields (PLQYs) and dissymmetry factor. It was found that the axially chiral scaffold attached with a cyanostilbene showed a pathway-dependent assembly route to form chiral luminescent liquid crystals and crystals upon fast and slow cooling, respectively. A significant enhancement of PLQYs (98.4%) and a dissymmetry factor (g_lum) value (2.1 × 10⁻²), and consequently, a high figure of merit (FM) of up to 0.02 was achieved in the chiral liquid crystal phase. Moreover, the liquid crystal and crystal phases showed the opposite CPL signals while maintaining the same circular dichroism signs. Through a thorough evaluation of UV absorption, CPL emission, wide-angle X-ray diffraction, and theoretical calculations, it was revealed that the reversal of the CPL sign was linked to distinct phases of excited state molecular packing. This research utilized a novel intrinsically axially chiral source to develop a pathway-dependent and higher-performance CPL materials.