Synthesis, photophysical and antioxidant properties of pyrrolo[3,2-c]carbazole and dipyrrolo[3,2-c:2′,3′-g]carbazole compounds

The synthesis of (6-ethyl-1,6-dihydropyrrolo[3,2-c]carbazol-2-yl)methanol 5 and (6-ethyl-6,11-dihydro-1H-dipyrrolo[3,2-c:2,3-g]carbazole-2,10-diyl)dimethanol 6 were achieved via the reduction of methyl pyrrolo carbazole carboxylate 3 and methyl dipyrrolo carbazole carboxylate 4, respectively. The structures of hydroxymethyl-pyrrolocarbazoles 5 and 6 were supported by FT-IR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, H-1 and C-13 NMR spectroscopy. The photophysical properties of the targeted compounds 3-6 were investigated by employing absorption and fluorescence spectroscopy in different common organic solvents. Also, the fluorescence lifetime ((F)) of the compounds was measured utilizing a time-correlated single-photon counting technique in tetrahydrofuran. Antioxidant activities of compounds 3-6 were determined by employing three different assays, namely DPPH radical scavenging, ABTS cation radical decolarization and cupric reducing antioxidant capacity. The results revealed that the ABTS cationic scavenging activity assay was found to be the most sensitive method for the determination of inhibition values.