Molecular Design and Optical Property Study of D–A– π –A Type Benzothiadiazole Derivatives

ABSTRACT A series of novel D–A– π –A structured benzothiadiazole (BTD) derivatives, incorporating triphenylamine as the donor and various secondary acceptors, were synthesized to investigate their multifunctional third‐order nonlinear optical (NLO) and photoluminescent properties. By strategically replacing the phenylene π ‐bridge with a furan ring, we achieved significant enhancement in both conjugation and intramolecular charge transfer (ICT) efficiency. Z‐scan measurements revealed exceptional NLO susceptibilities (χ (3) ) and second‐order hyperpolarizabilities ( γ ) up to 7.55 × 10 −11 and 12.10 × 10 −29 esu, respectively. Regarding luminescent performance, the furan‐bridged (FR) series exhibited pronounced solvatochromism with superior near‐infrared (NIR) emission reaching 716 nm, significantly red‐shifted compared to their phenylene‐bridged (BZ) analogues. Notably, BZ‐4 achieved a high fluorescence quantum yield of 94.6% in toluene, attributed to the suppression of non‐radiative transitions and its potential aggregation‐induced emission (AIE) characteristics. The remarkably high γ values and sensitive emission responses in phenylacetonitrile‐substituted derivatives are further ascribed to a secondary enhancement mechanism involving twisted intramolecular charge transfer (TICT) processes. This study demonstrates that the D–A– π –A architecture is a powerful strategy for developing high‐performance integrated NLO and NIR‐emissive materials.