N-Rich Fused Heterocyclic Systems: Synthesis, Structure, Optical and Electrochemical Characterization

A new class of N-rich fused heterocyclic compounds containing the triazolo-triazine moiety was synthesized and studied by cyclic voltammetry, UV/Vis spectroscopy, X-ray diffraction, and first principle computations. All the compounds show reversible or quasi-reversible reduction processes, with reduction potentials easily tunable within the class. LUMO ener-gies as low as –3.95 eV have been measured. The UV/Vis spectra show highly structured absorptions, indicative of rigid molecular skeletons. The solid-state packing is dominated by π–π stacking interactions, which are promoted by weak CAr–H···N interactions, whereas face-to-edge contacts (T contacts), typical of many fused hydrocarbons, are largely absent.