[1,2,5]Thia- and selenadiazolo[3,4-c]pyridines as efficient acceptors for D-A-D materials with emission in NIR spectral region.

Designing efficient emitters in the red and near-infrared (NIR) region remains a key challenge for next-generation optoelectronic materials. Here, we report four novel donor-acceptor-donor (D-A-D) type dyes synthesized via Suzuki cross-coupling reactions using 4,7-dibromo[1,2,5]thia- and selenadiazolo[3,4-c]pyridines as acceptor cores, paired with triphenylamine or N-benzylcarbazole donor fragments. All the dyes exhibit intense red and near-infrared (NIR) emission with photoluminescence quantum yields of up to 64%. Utilizing selenadiazolo[3,4-c]pyridines instead of sulfur-based acceptor leads to a red-shift luminescence maximum (λ) by approximately 60 nm and reduces the HOMO-LUMO gap to 1.4-1.6 eV. Importantly, the frontier orbital energies of the dyes fall within the ranges typical for efficient red and NIR OLED emitters, underscoring their relevance for device applications. These findings highlight the potential of chalcogen-modified pyridine-fused heterocycles as a versatile platform for designing efficient red/NIR-emitting materials for advanced optoelectronic applications.