Luminescent-Substituted Fluoranthenes-Synthesis, Structure, Electrochemistry, and Optical Properties

Six novel fluoranthene derivatives, namely, three terminally substituted and three bis(fluoranthene) units with fluorene, bithiophene, and carbazole spacers, were obtained through [2+2+2] cycloaddition and characterized completely. Based on the conducted studies, the obtained derivatives can be classified as donor-acceptor (D-A) and acceptor-donor-acceptor (A-D-A) systems, in which the fluoranthene unit acts as an electron-withdrawing unit. The optical results revealed that novel fluoranthene derivatives absorb light in the range λ=236-417 nm, which originates from a π→π^* transition within the conjugated system. The compounds exhibit fluorescence that range from deep blue to green, which mainly arises from intramolecular charge transfer (ICT) states. High Stoke shifts and high quantum yields in solution (ϕ=0.22-0.57) and in the solid state (ϕ=0.18-0.44) have been observed for fluoranthene derivatives. All the derivatives display multistep oxidation processes at low potentials. The electronic structure of the presented compounds is additionally supported by time-dependent DFT computations.