Bent π‐Conjugated Systems Composed of Three‐Dimensional Benzoannulenes

<jats:title>Abstract</jats:title><jats:p>This article describes bent π‐conjugated systems composed of alternating <jats:italic>o</jats:italic>‐phenylene and <jats:styled-content style="fixed-case"><jats:italic>Z</jats:italic></jats:styled-content>‐vinylene units. <jats:italic>all</jats:italic>‐<jats:styled-content style="fixed-case"><jats:italic>Z</jats:italic></jats:styled-content>‐[<jats:italic>n</jats:italic>]<jats:styled-content style="fixed-case">B</jats:styled-content>enzo[4<jats:italic>n</jats:italic>]annulenes are higher homologues of dibenzocyclooctatetraene (<jats:styled-content style="fixed-case">DBCOT</jats:styled-content>) with a concave π system, and attempts were made to convert [20]‐ and [24]annulenes having partial belt structures of fullerenes and carbon nanotubes into [10]‐ and [12]phenacenes. A bent π‐conjugated system composed of two <jats:styled-content style="fixed-case">DBCOT</jats:styled-content> units showed dynamic <jats:italic>syn</jats:italic>–<jats:italic>anti</jats:italic> equilibrium in solution and behaved as dynamic molecular tweezers (<jats:styled-content style="fixed-case">DMT</jats:styled-content>s). The <jats:italic>syn</jats:italic> isomers of the <jats:styled-content style="fixed-case">DMT</jats:styled-content>s formed blue charge‐transfer complexes with <jats:styled-content style="fixed-case">DDQ</jats:styled-content> in solution, and this complexation and color change were applied to thermochromism. Furthermore, <jats:styled-content style="fixed-case">DMT</jats:styled-content>s having two <jats:styled-content style="fixed-case">CN</jats:styled-content> groups on each <jats:styled-content style="fixed-case">COT</jats:styled-content> ring exhibited crystalline‐state emission in the presence of solvent molecules, although almost no emission was observed in solution or the solid state. Based on this crystalline‐state emission, a vapochromic system was established. The multifunctional properties of <jats:styled-content style="fixed-case">DMT</jats:styled-content>s caused by the flexibility of the nonplanar π system are summarized.</jats:p>