Mixed valence salts based on carbon-centered neutral radical crystals

Abstract

Organic neutral radicals have been predicted to exhibit various electronic functions such as electrical conduction. However, most organic neutral radicals are insulators, because they cannot form sufficient intermolecular interactions due to the bulky substituent groups required for stabilization. Here we report that one-dimensional assemblies of carbon-centered neutral π-radicals, namely 4,8,12,trioxotriangulene derivatives, possess effective conducting pathways as a result of strong intermolecular interactions based on two-electron-multicenter bonding. The columns of trioxotriangulene derivatives with weak π-dimerization and uniform π-stacking exhibit semiconducting behaviors, with high conductivities of ~10−3 S cm−1 as a single component purely organic molecular system. We exploit this general tendency to form one-dimensional assemblies, and the large 25 π-electronic system with a robust condensed polycyclic structure, to obtain mixed-valence salts consisting of neutral radicals and the corresponding anionic species with a higher room-temperature conductivity of 1–125 S cm−1.