Synthesis and opto-electrochemical properties of tribenzo[a,c,i]phenazine derivatives for hole transport materials

In this work, five novel 3,6-disubstituted-tribenzo[a,c,i]phenazine (2-6) derivatives were synthesized in good yield by employing a palladium catalyzed C-N bond forming amination reaction and fully characterized. Photophysical properties of 2-6 were studied both in solvent and neat solid film by UV-vis absorption, fluorescence spectroscopy and electrochemical properties by cyclic voltammetry. Absorption spectra of 2-6 showed intramolecular charge transfer (ICT) transitions in the range of 460-512 nm in solution. The HOMO and LUMO energy levels of 2-6 are in the range of -5.18 to -5.35 eV and -3.06 to -3.17 eV respectively with electrochemical bandgap within the range of 2.12-2.29 eV. HOMO energy levels of 2-6 are comparable with most commonly used hole transporting materials such as TPD, alpha-NPD and spiro-OMe-TAD etc. and thus make them potential candidates for the hole transporting material in organic electronics.