[<i>n</i>]Helicene Diimides (<i>n</i> = 5, 6, and 7): Through-Bond versus Through-Space Conjugation

Abstract

The interactions between auxochromic groups in π-conjugated functional molecules dictate their electronic properties. From the standpoint of potential applications, understanding and control of such interactions is a vital requirement for the material design. In this communication, we describe the design, synthesis, and functional properties of a novel class of helically chiral diimide molecules, namely, [<i>n</i>]HDI-OMe (<i>n </i>= 5, 6, and 7), in which two imide units are connected via an [<i>n</i>]helicene skeleton. The experimental results supported by quantum chemical calculations reveal that the helical backbone in these molecules offers not only through-bond but also through-space conjugation between imide groups, which leads to distinct optical and electrochemical properties when compared to the related [<i>n</i>]helicenes and rylene diimides.