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-propynylidenel]-9,10-dihydroanthracenes

A bis(enediyne) system utilizing anthraquinodimethane as a platform for a redox-active substructure that bears azulenes as pi-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. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).