Emergence of circularly polarized luminescence from achiral o-carborane-based molecules through molecular vibrations coupled with intramolecular charge transfer in solid states

Abstract

Realizing circularly polarized luminescence (CPL) through molecular vibrations coupled with intramolecular charge transfer is a significant yet challenging issue in chiral optoelectronic materials. Herein, CPL signals emerged from two novel achiral o-carborane dyads (o-1 and o-2) through molecular vibrations coupling with intramolecular charge transfer in solid states. Notably, the triplet-hybridized local and intramolecular charge-transfer (³HLCT) emissions of o-1 were dynamically transferred to triplet locally-excited (³LE), resulting in enhanced triplet emission intensity. Meanwhile, o-2 exhibited triplet negative thermal quenching (NTQ), which arose from a significant degree of triplet charge separation between electron-withdrawing and electron-donating units. More importantly, those combined effects induced excited molecular symmetry breaking, leading to intense CPL with significant luminescence dissymmetry factor (g_lum) values. Additionally, the hydrostatic pressure-dependent emissions of the three-dimensional structure of the o-carborane unit were investigated. This study offers a valuable model for exploring the fundamental nature of chirality arising from achiral materials.