Planar chiral AIEgens based on [2.2]paracyclophane as efficient solid-state deep red circularly polarized luminescent emitters

Abstract

In this work, a series of [2.2]paracyclophane-based 4-(dicyanomethylene) -4H-pyran compounds (2a−2d) with aggregation-induced emission (AIE) and circularly polarized luminescence (CPL) properties were designed and synthesized. These compounds exhibit orange and deep red emissive fluorescence at 585–686 nm with high fluorescence quantum yields (Φf) of 40–97% in solid-state. More importantly, (Rp)/(Sp)-2a−2b form different aggregation states due to the influence of different substituents, resulting in different Cotton effects. Moreover, (Rp)/(Sp)-2a−2b display aggregation-induced circularly polarized luminescence (AICPL) signals in the deep red region with moderate luminescence dissymmetry factors (1.4–1.9 × 10−3). These photophysical properties are rationalized by single crystal structure analysis, TD-DFT calculations, cyclic voltammetry and SEM. These results clearly demonstrate the introduction of strong electron-accepting group on [2.2]paracyclophane derivatives to enhance the ICT process is an efficient approach to construct planar chiral deep red circularly polarized luminescence emitters.