Structural, Spectroscopic, Electrochemical, and Electroluminescent Properties of Tetraalkoxydinaphthophenazines: New Solution-Processable Nonlinear Azaacenes

A series of solution-processable tetraalkoxy-substituted dinaphtho­[2,3-<i>a</i>:2′,3′-<i>h</i>]­phenazines were synthesized by reductive functionalization of indanthrone (6,15-dihydrodinaphtho­[2,3-<i>a</i>:2′,3′-<i>h</i>]­phenazine-5,9,14,18-tetraone), an old intractable dye. The melting point of these new compounds was found to decrease from 204 °C to 98 °C upon extension of the number of carbons from 4 to 12 in the alkoxy substituent. All derivatives show a strong tendency to self-organize in 2D as evidenced by STM investigations of monolayers deposited on HOPG. The 2D structure is less dense and shows different alkoxy group interdigitation pattern as compared to the 3D structure determined from the X-ray diffraction data obtained for the corresponding single crystals. Electrochemical, absorption, and emission properties of tetraalkoxy-substituted dinaphtho­[2,3-<i>a</i>:2′,3′-<i>h</i>]­phenazines, studied in solution, are essentially independent of the length of the alkoxy substituents. All derivatives exhibit high photoluminescence quantum yield, approaching 60%. When molecularly dispersed in a solid matrix consisting of poly­(9-vinylcarbazole) (PVK) (60 wt %) and (2-<i>tert</i>-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) (40 wt %) (so-called “guest/host configuration”), they show green electroluminescence due to an effective energy transfer from the matrix to the luminophore. The best light-emitting diodes were obtained for the butoxy derivative showing a luminance approaching 1500 cd/m² and a luminous efficiency over 0.8 cd/A