Discovery of Novel D-A and D-π-A Structured Carbazole-Based Formazan Dyes: Synthesis, Characterization, and Spectroscopic Studies

In the current study, new carbazole-based formazan dyes, D-A and D-pi-A, were synthesized, and their spectroscopic properties were studied for the first time. For this aim, carbazole aldehyde compounds were modified by the derivatization of carbazole, a natural electron-donor compound, from 3- and 9-position. Then, hydrazone derivatives were synthesized from these aldehyde derivatives. Finally, D-A (5A-C) and D-pi-A (6A-C) carbazole-formazan dyes were obtained by the interaction of the hydrazone compounds with p-substituted aniline. After characterization of the structures of these compounds, photophysical properties of the carbazole-formazans were studied in the different polarity media (i.e., acetonitrile, toluene, and chloroform) in order to detect the solvent effects. Because of the pi-conjugated bridge and the electron acceptor nitro group at the para position, D-pi-A structured carbazole-formazan dye 6C showed the highest Stokes shift of 155 nm.