Four different isomeric azadibenzo[a,e]pyrenes are prepared by combination of Pd-catalyzed Sonogashira and Suzuki cross-coupling, Brønsted acid mediated cycloisomerization and Pd-catalysed CH-activation reactions. The optical and electrochemical properties are studied by experimental and theoretical methods.

Abstract

Four different isomeric azadibenzo[a,e]pyrenes (benzo[4,10]anthra[9,1-gh]isoquinolines and benzo[4,10]anthra[1,9-fg]isoquinolines) were prepared by combination of Pd-catalyzed Sonogashira and Suzuki cross-coupling, Brønsted acid mediated cycloisomerization and Pd-catalysed CH-activation reactions. The optical properties have been studied by steady-state absorption and emission spectroscopy in different solvents and during acid titration. Trifluoroacetic acid protonation strongly affects absorption and emission properties, with variations depending on the position of the nitrogen atom of the specific compound. Electrochemical analysis showed distinct oxidation and reduction potentials. DFT calculations provided further insights into electronic properties.