Preparation, Redox Properties, and X-ray Structures of Electrochromic 11,11,12,12-Tetraarylanthraquinodimethane and Its Bianthraquinodimethane Analogue: Drastic Geometrical Changes upon Interconversion with Dicationic Dyes

Tetrakis(4-methoxyphenyl)anthraquinodimethane 1(b) with a bent geometry undergoes reversible redox interconversion with twisted dication 1(t)(2+) exhibiting a vivid change in color (electrochromism) accompanied by a drastic structural change. Electrochemical oxidation of bianthraquinodimethane 2(b) with a doubly bent structure to bianthrylidene-type twisted dication 2(t)(2+) proceeded smoothly, whereas the reverse conversion was less effective because 2(t)(2 center dot) generated upon reduction of 2(t)(2+) is a long-lived species to undergo side reactions.