Symmetry-Breaking Directed Assembly in Achiral Point Groups for Circularly Polarized Room-Temperature Phosphorescence.

Li, Qihuan; Song, Yizhou; He, Jiaqi; Zhang, Junsheng; Zou, Guo; Cheng, Yixiang · Adv Mater · 2025

basic_science · Level V

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Abstract

Very recently, considerable attention has been given to pure organic circularly polarized room-temperature phosphorescent (CP-RTP) materials due to their unique photophysical properties. However, the directed construction of optically active phosphorescent signals within achiral systems remains a formidable challenge. In this study, two achiral crystals, 2CN4S and 2F4S, belonging to the achiral point groups 2/m and <math xmlns="http://www.w3.org/1998/Math/MathML"> <semantics><mover><mn>1</mn> <mo>¯</mo></mover> <annotation>$\bar{1}$</annotation></semantics> </math> , exhibit strong CP-RTP emission with high photoluminescence dissymmetry factors (g<sub>lum</sub>) up to 5.5 × 10<sup>-2</sup> (543 nm) and 4.3 × 10<sup>-2</sup> (550 nm), respectively. This phenomenon is attributed to the intrinsic mirror-antiparallel molecular conformations induced by the targeted substitution of cyano/fluoro groups, which spontaneously assemble into symmetry-breaking helical superstructures through synergistic C─H···N hydrogen bonding and π-π interactions. This work not only establishes a novel approach for CP-RTP material design but also overcomes structural constraints in optically active materials within achiral point group systems.