Résumé : Synthesis, isolation, and characterization of isomerically pure syn-and anti-anthradiindole (ADI) derivatives are described. The anti-and syn-ADI structures are demonstrated by 13C NMR spectroscopy and by single-crystal X-ray diffraction. The spectroscopic and electrochemical properties as well as the stability of these newly synthesized π-conjugated systems are evaluated and supported by quantum-chemical calculations. © 2013 American Chemical Society.