No abstract

New N-alkyl-substituted heterocyclic system imidazo [4,5-a]quinindolines (imidazo[4,5-f]-indolo[2,3-b]quinolines) were synthesized by one pot reaction of 1-alkyl-5-nitro-1H-benzimidazole with 2-(1-alkyl-1H-3-indolyl)acetonitrile in basic media via the nucleophilic substitution of hydrogen and concomitant cyclisation in good yields. Physical spectral (UV-vis, IR, NMR and fluorescence) and analytical data have established the structures of synthesized compounds. The fluorescence properties of these new heterocyclic compounds were studied. The fluorescence of all compounds was very intense and fluorescence quantum yields were very high (> 0.70). Solvent effects on absorption and emission spectra of these dyes have also been studied; the absorption and emission bands in polar solvents undergo a red shift. Density function theory (DFT) calculations of one structure by using the B3LYP hybrid functional and the 6-311+G(d,p) basis set to provide the relevant frontier orbitals were also performed.