Stereoselective Synthesis and Characterization of Indenone Azine‐Based Electron‐Accepting π‐Conjugated Systems

Abstract

AbstractIndenone azines, in which the exocyclic C=C bond in dibenzopentafulvalene is replaced by an azine moiety (C=N−N=C), have been synthesized as novel electron‐accepting π‐conjugated scaffolds. Structural modulation at the 7,7′‐positions of indenone azines enabled stereoselective syntheses of diastereomers in which the configurations of the two C=N bonds are E,E or Z,Z. X‐ray crystallographic analyses revealed that all the indenone azines exhibit high coplanarity in contrast to the twisted frameworks of dibenzopentafulvalene derivatives, resulting in the formation of densely π‐stacked structures. Electrochemical measurements and quantum chemical calculations revealed the electron‐accepting character of indenone azines comparable to isoindigo dyes. In particular, the intramolecular hydrogen bonds of 7,7′‐dihydroxy‐substituted derivatives impart enhanced electron‐accepting character and significantly red‐shifted photoabsorption. This study demonstrates that indenone azines represent a promising candidate as electron‐accepting building blocks for optoelectronic materials.