Synthesis, photophysical and electrochemical properties of a carbazole dimer-based derivative with benzothiazole units.

A novel A-π-D-π-D-π-A type compound, containing two benzothiazole rings as electron acceptors and two N-ethylcarbazole groups as electron donors, (E)-1,2-bis(3-(benzothiazol-2-yl)-9-ethylcarbazol-6-yl)ethene (BBECE), was synthesized and characterized by elemental analysis, NMR, MS and thermogravimetric analysis. Electrochemical property of compound BBECE was studied by cyclic voltammetry analysis. The absorption and emission spectra of BBECE was experimentally determined in several solvents and simultaneously computed using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The calculated absorption and emission wavelengths are coincident with the measured data. The lowest-lying absorption spectra can be mainly attributed to intramolecular charge transfer (ICT), and the fluorescence spectra can be mainly described as originating from an excited state with intramolecular charge transfer (ICT) character. The molecular orbitals (HOMO and LUMO), the ionization potential (IP), the electron affinity (EA) and reorganization energy of compound BBECE were also investigated using density functional theory (DFT). The results show that compound BBECE exhibited excellent thermal stability and electrochemical stability as well as high fluorescence quantum yield, indicating its potential applications as an excellent optoelectronic material in optical fields.