Co-assembly of chiral copper(I) complexes and achiral polymer for enhanced circularly polarized luminescence

Abstract

Circularly polarized luminescence (CPL) has attracted growing attention for their promising applications in chiral functional devices. Achieving CPL materials with both high luminescence dissymmetry factors (g_lum) and emission efficiency is attractive but remains great challenges. In this study, a pair of chiral Cu(I) complexes named R/S-CuI with C₂ symmetry were synthesized, exhibiting no emission in solution and weak CPL with g_lum = ± 3.3×10⁻³ in crystalline state. Transparent chiral films (R/S-CuI-film) were developed through the co-assembly of R/S-CuI and achiral polymer PMMA. The films show bright green luminescence with the quantum yields about 200 times higher than those in crystalline state. Meanwhile, the maximum |g_lum| value is also amplified by approximately 2.5 times, reaching to 8.7×10⁻³. Mechanism investigation suggests that the notable enhancement of luminescence efficiency can be ascribed to the restriction of the intramolecular motions and the elimination of the oxygen quenching effect, while the improvement in g_lum values may be explained by the chirality transfer from the axially chiral molecule R/S-CuI to the achiral polymer PMMA. Furthermore, R/S-CuI-film were used for advanced information encryption applications based on its CPL characteristics. This work may provide new inspirations for the construction of CPL-active films with high performance, thereby expediting their further development.