Electrochromic Application of an Enediyne Scaffolding as a Redox‐Active Chromophore − Synthesis and Redox Behavior of 9,10‐Bis[3‐(6‐azulenyl)‐1‐(6‐azulenylethynyl)‐2‐propynylidene]‐9,10‐dihydroanthracenes

A bis(enediyne) system utilizing anthraquinodimethane as a platform for a redox‐active substructure that bears azulenes as π‐electron‐accepting groups at the periphery has been prepared by a simple one‐pot reaction involving repeated Pd‐catalyzed alkynylation of 6‐bromoazulenes with the bis(enediyne). The novel bis(enediyne)s exhibited two, one‐step two‐electron redox properties under electrochemical reduction conditions together with a significant color change owing to the generation of a closed‐shell cyanine‐type substructure by the two‐electron reduction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)