A bow-like axially chiral cycloparaphenylene with simultaneously enhanced photoluminescence quantum yield and dissymmetry factor

Abstract

Cycloparaphenylenes (CPPs) with unique luminescent properties and well-defined dimensions are considered as ideal blocks for achieving excellent circularly polarized luminescence performance. Chiral CPPs face challenges in simultaneously achieving both high photoluminescence quantum yield (PLQY) and luminescence dissymmetry factor (g_lum) due to their unique size effects. In this work, a bow-shaped axially chiral CPP, named 4CzZ[6]CPP, was designed and synthesized by utilizing a carbazole-modified donor–acceptor axially chiral unit through a chirality embedding strategy. The topological structure and photophysical properties were elucidated through crystallography and spectroscopy. Remarkably, 4CzZ[6]CPP showed an exceptional PLQY of 74.4% due to the interaction charge transfer (ICT) process and the constrained conformation. In particular, the (R/S)-4CzZ[6]CPP exhibited a maximum |g_lum| of up to 6.43 × 10⁻³ because of the rigid structure, representing a 2.5-fold enhancement compared to the chiral precursors, which was confirmed by theoretical calculations. Additionally, a high circularly polarized luminescence brightness (B_CPL) of 344 M⁻¹ cm⁻¹ was achieved, which represents a new record among chiral CPPs constructed by a chirality embedding strategy reported to date.