Enhanced chiroptical activity for narrow deep-blue emission in axial chiral frameworks via three-dimensional interlocking

Abstract

The advancement of desirable circularly polarized luminescence (CPL) emitters is predominantly constrained by the effective regulation of magnetic and electric transition vectors, particularly within the deep-blue spectral domain. Herein, we present four pairs of novel chiral emitters with systematically varied molecular rigidity, symmetry, and chiral centers to elucidate the intrinsic coupling of key molecular parameters influencing their chiroptical properties. Notably, the incorporation of appropriate intramolecular 3D-interlocking within a natural binaphthyl chirality skeleton offers an effective approach to achieving both significantly narrowed full width at half maximum (FWHM, as low as 18 nm) and substantially enhanced chiroptical activity (luminous dissymmetry factor, g_PL, up to 3.0 × 10⁻³). Additionally, introducing a secondary chiral center closely parallel to the primary chiral plane facilitates strong chiral–chiral interactions, further affording a 50% improvement in their g_PL values. As a demonstration, vacuum-deposited circularly polarized organic light-emitting diodes incorporating these pure fluorescent emitters exhibit outstanding electroluminescent performance, with maximum external quantum efficiency exceeding 5.35%, favorable FWHM of approximately 25 nm, and extreme CIE_y values below 0.03.