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.