Engineering circularly polarized luminescence through symmetry manipulation in achiral tetraphenylpyrazine structures

Abstract

Symmetry breaking, a critical phenomenon in both natural and artificial systems, is pivotal in constructing chiral structures from achiral building units. This study focuses on the achiral molecule 8,8',8'',8'''-((pyrazine-2,3,5,6-tetrayltetrakis(benzene-4,1-iyl))tetrakis (oxy))tetrakis (octan-1-ol) (TPP-C8OH), an aggregation-induced emission (AIE) molecule, to explore its symmetry breaking behavior in supramolecular assembly. By analyzing TPP-C8OH in various solvents—both non-chiral and chiral—we find that chiral solvents significantly enhance the molecule's symmetry breaking and chiroptical properties. Specially, alcohol solvents, particularly dodecyl alcohol, facilitate the formation of helical structures with both left-handed (M) and right-handed (P) helices within single twisted nanoribbons. This observation contrasts with previously reported symmetry breaking phenomena in assembly systems. Chiral solvents induce assemblies with distinct helical orientations, resulting in notable circularly polarized luminescence (CPL) and circular dichroism (CD) signals. This study elucidates the impact of solvent choice on symmetry breaking and chiral assembly, offering insights into the design of advanced chiral materials with tailored self-assembly processes.