Synthesis of 5-Azatetracene and Comparison of Its Optical and Electrochemical Properties with Tetracene

A four-step route for the synthesis of 5-azatetracene (benzo[b]acridine) has been developed, employing a base-catalysed Friedlander condensation reaction between 3-amino-2-napthaldehyde and cyclohexanone as the key step followed by dehydrogenation of the intermediate. The optical and electrochemical properties of the 5-azatetracene were investigated by UV-vis and photoluminescence spectroscopy, and by cyclic voltammetry and compared with those of tetracene. It is found that 5-azatetracene shows broader absorption in the visible region than tetracene, exhibits a higher luminescence quantum efficiency, and possesses a lower-lying LUMO level and smaller HOMO-LUMO band gap. Time-resolved PL spectroscopy was used to elucidate the reasons for the more efficient luminescence of 5-azatetracene. Field-effect transistor measurements revealed the ambipolar nature of charge transport in 5-azatetracene.