Serendipitous Formation of Semiconducting Semi-Nindigo Indigoid by the Degradation of Diindolopyrrole

We report the serendipitous discovery and synthesis of an indigoid “semi-Nindigo” (2) via oxidation of a diindolopyrrole (1). The reaction of 2 with BF₃Et₂O affords the borylated derivative (3). The electronic spectra of 2 and 3 possess intense long wave absorptions near 600 and 650 nm. Compound 3 is weakly emissive in the near-infrared. Thin-film OFETs fabricated with 1 and 2 both exhibited hole mobility of 10^–5 and 10^–3 cm²/(V s), respectively.