Dibenzofuran[a]‐Fused BODIPYs: Synthesis, Photophysical Properties, and N₂O₂‐Boron‐Chelation Towards NIR Materials for Application in Organic Photodetectors

Highly annulated boron‐dipyrromethenes (BODIPYs) were synthesized with the objective to develop a near‐infrared (NIR)‐absorbing photodetector. Post‐functionalization of the dibenzoBODIPY scaffold enabled it to fuse with the dibenzofuran heterocycle at the a ‐bond of the pyrrole unit to give the related dyes 1 and 2 , which absorb far‐red light in tetrahydrofuran. Further structural modification by intramolecular B , O ‐chelation of 2 yielded the benzo[1,3,2]oxazaborinine‐containing dye 14 having an intense absorption band with a λ _max value of 812 nm ( ϵ =1.3×10 ⁵  M ⁻¹  cm ⁻¹ ), as rationalized by time dependent density functional theory (TD‐DFT)/DFT calculations. Dye 14 exhibited unique emission properties, wherein irradiation at 375 nm led to a dual emission at 822 nm ( Φ =5.1 %) and 470 nm ( Φ =7.8 %), which could be attributed to the electronic non‐adiabatic coupling due to the large energy difference between the S ₂ and S ₁ states, according to the anti‐Kasha rule. Using a resistance‐heating‐type vacuum‐deposition method, the rigid π‐conjugated structure of 14 enabled its application as an NIR photodetector in a single‐component device (indium tin oxide/ 14 /Al). Current–voltage ( J – V ) measurements under photoirradiation at 870 nm (120 μW cm ⁻² ) produced a photocurrent of 6.05×10 ⁻⁷  A cm ⁻² at a bias potential of 0.1 V.