Pushing to the low limits: tetraazaanthracenes with very low-lying LUMO levels and near-infrared absorption.

Here we propose the combination of the 4-alkoxythiazole donor motif with highly photostable tetraazaanthracenes as electron-acceptor units. The segregated frontier orbitals in these dyes afford optical band gaps of 1.4-1.1 eV. Cyclic voltammetry confirmed the very low-lying LUMO levels that are attributed to the highly electron-deficient tetraazaanthracene moiety.