Tunable circularly polarized luminescence behaviors caused by the structural symmetry of achiral pyrene-based emitters in chiral co-assembled systems

Abstract

The regulation of circularly polarized luminescence (CPL) behavior is of great significance for practical applications. Herein, we deliberately designed three achiral pyrene derivatives (Py-1, Py-2, and Py-3) with different butoxy-phenyl substituents and the chiral binaphthyl-based inducer (R/S-B) with anchored dihedral angle to construct chiral co-assemblies, and explored their induced CPL behaviors. Interestingly, the resulting co-assemblies demonstrate tunable CPL emission behaviors caused by the structural symmetry effect of achiral pyrene-based emitters during the chiral co-assembly process. And in spin-coated films, the dissymmetry factor (g_em) values were 9.1 × 10^-3 for (R/S-B)₁-(Py-1)₁₀, 5.6 × 10^-2 for (R/S-B)₁-(Py-2)₇, and 8.6 × 10^-4 for (R/S-B)₁-(Py-3)₁, respectively. The strongest CPL emission (|g_em| = 5.6 × 10^-2, λ_em = 423 nm, QY = 34.8 %) was detected on (R/S-B)₁-(Py-2)₇ due to the formation of regular and ordered helical nanofibers through the strong π-π stacking interaction between the R/S-B and the achiral Py-2 emitter. The strategy presented here provides a creative approach for progressively regulating CPL emission behaviors in the chiral co-assembly process.

Keywords: Chiral amplification; Chiral co-assemblies; Circularly polarized luminescence; Structural symmetry; Tunable chirality.