Chemical design of carbazole dendrons: Optical properties and DFT analysis

Abstract In this study, the synthetic approach, structural characterization and optical properties of series of carbazole derivatives with different functional groups were investigated in order to provide the foundations and develop novel materials with required characteristics suitable for obtaining opto- and electrical devices. Such molecules can act as building blocks for more complex organic molecules. The compositions and structural characteristics of them were determined by the elemental analysis, infrared and NMR spectroscopy, mass-spectrometry, thermal analysis, UV/Vis and fluorescence spectroscopy. The geometry optimization of the most stable conformers was performed using TDDFT calculations which were also employed to gain insight into the experimental data. Optical measurements and computational studies imply that the compounds are non-planar due to steric repulsion of hydrogen atoms and take a curved conformation with angles 45.5°–55.9° between the carbazole and aryl substituents planes. All synthesized compounds have intense fluorescence in solution with quantum yields from 18% to 50% and exhibit solid state fluorescence from bluish-white to blue-green, that can be adjusted by introducing various substituents focusing on functionalization at the 3,6- and 9-positions.