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

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 1¯1̄ , exhibit strong CP-RTP emission with high photoluminescence dissymmetry factors (glum) up to 5.5 × 10-2 (543 nm) and 4.3 × 10-2 (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.