Exploring the electronic structure of an organic semiconductor based on a compactly fused electron donor-acceptor molecule

A Mott-type semiconductor based on a compactly fused and partially oxidized electron donor-acceptor (D-A) molecule was recently prepared and identified to exhibit a large room-temperature conductivity of 2 S cm^-1. In a marked contrast to the organic conductors characterized by relatively well decoupled and segregated uniform stacks of D and A moieties, the formally half-oxidized tetrathiafulvalene donors of the actual compound are organized in columnar π stacks only, whereby the coplanar electron-acceptor units, namely benzothiadiazole, are closely annulated along their ridges. Herein, we present a theoretical study that explores the electronic structure of this novel type of organic semiconductor. The highly symmetric-solid state material behaves as a one-dimensional electronic system with strong antiferromagnetic interactions (coupling constant>200 cm^-1). The unique shape and local dipole of this redox-active fused electron D-A molecule lays the basis for further investigations of the collective electronic structure, mainly in the function of different counterions embedded in the crystalline lattice.