Synthesis and properties of doubly diphenylene-fused benzopyrrolo[1,4]diazocine with a [7-8-7] successive ring-fused structure

Abstract

Abstract We explored a π-electronic system with a successively fused [7-8-7]-membered ring structure. X-ray analysis revealed its nonplanar structure with a mean plane deviation (MPD) of 1.53 Å. Compared with a reference compound with a [7-6-7]-membered ring structure (MPD: 0.38 Å), the incorporation of an 8-membered ring induced larger nonplanarity. On the other hand, replacing the 6-membered ring with an 8-membered ring induced a smaller strain in energy, as suggested by using DFT calculations. The π-orbital axis vector analysis showed that the nonplanarity was mainly dictated by torsion, not pyramidalization.