Helical π-Extension for Efficient Chiral TADF: A Theoretical Design of Multiresonance Emitters Modulated by Long-Range Charge Transfer

Balancing short-range (SRCT) and long-range charge transfer (LRCT) is essential for designing efficient chiral multiresonance thermally activated delayed fluorescence (MR-TADF) emitters. Using the density functional theory (DFT) and time-dependent DFT, we design a series of heteroaromatic-functionalized helicene derivatives and demonstrated that helical π-extension, driven by heteroaromatic rings, effectively modulates frontier orbital distribution. This balances SRCT within the MR core and LRCT across the helical periphery, leading to narrow singlet-triplet gaps, enhanced spin-orbit coupling, and the emergence of dual reverse intersystem crossing (RISC) channels (T₁ → S₁ and T₂ → S₁) for efficient triplet harvesting. The chiral helical structure further preserves narrowband emission while boosting chiroptical responses. This work confirms heteroaromatic-engineered helical π-extension as an effective design strategy for high-performance chiral MR-TADF materials, providing theoretical guidance for regulating charge-transfer and excited-state dynamics in future molecular design.