One‐Dimensional Polycyclic Aromatic Hydrocarbons Incorporating Multiple Dithiafulvene Units—Novel Multi‐Redox and Electrochromic Systems

Abstract

ABSTRACT The combination of polycyclic aromatic hydrocarbons (PAHs) and dithiafulvene (DTF) units provides large π‐conjugated scaffolds with multi‐redox behavior. Here, we present the synthesis and properties of PAHs containing seven or nine alternating and fused six‐ and five‐membered rings and three or four DTF units located along the PAHs, tri‐DTF and tetra‐DTF PAH scaffolds. The synthesis relied on the generation of PAH cores with carbonyl groups at the five‐membered rings to allow for Horner–Wadsworth–Emmons reactions to introduce the DTF units. These planar molecules exhibited very strong associations in neutral and oxidized states, and the various redox states had distinct UV–vis–NIR absorptions. Proceeding from an odd number to an even number of DTF units had a remarkable consequence for the redox properties. Thus, cyclic voltammetry revealed the tri‐DTF PAH to undergo stepwise one‐electron oxidations to form the trication with a broadened first oxidation wave owing to associations. Instead, the radical cation of the tetra‐DTF PAH underwent a single three‐electron oxidation, signaling an exceptional driving force for generating the tetracation. By electrocrystallization both mixed‐valence neutral–radical cation and radical cation salts were generated. These multi‐DTF PAHs are particularly interesting as potential components for electrochromic and conducting materials or as redox‐controllable tectons for molecular self‐/disassembly.