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

Abstract

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