Naphthalimide-fused BODIPYs via one-pot quadruple C-H activation: ultra-low LUMO n-type semiconductors with efficient near-infrared emission.

Near-infrared (NIR) n-type organic semiconductors with low-lying LUMO levels are essential building blocks for advanced optoelectronics, yet their development is hindered by laborious multi-step synthesis, insufficient electron affinity and limited stability. Herein, we report the precise synthesis and optoelectronic properties of a series of naphthalimide (NMI)-fused BODIPY derivatives as near-infrared absorbing n-type organic semiconductors, accessed through a palladium-catalyzed one-pot quadruple C-H activation strategy that constructs the fused conjugated framework in a single step. This annulation extends the large π-conjugated system and enables a favorable face-to-face molecular stacking in the crystalline state. The resulting dyes exhibit efficient NIR emission (Φ = 0.35-0.43), high molar absorptivity (ε up to 1.85 × 105 M-1 cm-1), and excellent photostability. Critically, NMI fusion dramatically lowers the LUMO energy to as low as -4.32 eV, enabling reversible multi-electron reduction. Chemical reduction with cobaltocene generates stable radical anions characterized by a diagnostic NIR absorption and a sharp EPR signal (g = 2.003). Solution-processed organic field-effect transistors confirm n-type charge transport. This work establishes a concise, modular synthesis of NMI-fused BODIPYs with an unprecedented combination of ultralow LUMO levels, stable radical anions, and efficient NIR emission, providing a versatile platform for organic electronics and beyond.