Structural Engineering of Chiral Naphthalene-Based Sandwich Emitters: Circularly Polarized Luminescence and Modulation of Charge-Transfer Mechanisms

Constructing chiral multichannel through-space charge transfer (TSCT) emitters presents a significant challenge due to difficulties in synthesis and the need for chiral resolution. Herein, two chiral multinaphthalene compounds, (S,S)-2,3-NpE and (S,S)-1,8-NpE, were synthesized via a one-pot nucleophilic aromatic substitution. Their photophysical, chiroptical, and structural properties were systematically investigated. UV–vis and fluorescence studies revealed significant charge transfer-based absorptions and emissions. Chiroptical studies confirmed strong Cotton effects and circularly polarized luminescence (CPL) with high emission dissymmetry factors of 6.4 × 10–3, exhibiting remarkable chirality transfer from naphthalene-based structures to spatial charge transfer emission. Single-crystal structural analysis demonstrated a unique sandwich-like molecular architecture, highlighting the role of molecular geometry in enabling TSCT. Time-dependent density functional theory calculations provided nuanced insights into the excited-state electronic structures. Frontier molecular orbital and hole–electron analyses unveiled distinct excitation mechanisms: (S,S)-2,3-NpE demonstrated a hybridized locally excited and charge transfer (HLCT) character, while (S,S)-1,8-NpE predominantly exhibited TSCT. These findings emphasize the importance of precise structural design in tuning charge transfer and photophysical behaviors, paving the way for future exploration of functionalized chiral materials.