Metal-free Annulation at the Ortho- and Bay-Positions of Perylene Bisimide Leading to Lateral π-Extension with Strong NIR Absorption

A novel ortho/bay annulation reaction of perylene bisimide (PBI) has been explored in a single step synthetic procedure using perylene bisimide 1 and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) in the absence of any metal catalyst. The single crystal solid-state X-ray diffraction structure showed a distorted framework of DBU-fused PBI 2. Compound 2 exhibited intense near-infrared absorption up to 950 nm. Reversible protonation and deprotonation accompany drastic changes in the photophysical characteristics. Further, the reaction of perylene biscarboxyanhydride with DBU offered a caprolactam ring-substituted perylene bisimide 3.