Redox and Emission Properties of Triazolo-Triazole Derivatives and Copper(II) Complexes

The hydrolysis reactions of triazolo–triazole derivatives, which are characterized by the presence of substituents of different electronic character (electron donor or acceptor) on the bicycle, in 0.5 mol·dm−3 NaCl as ionic medium, at 25 °C, have been investigated. Acid–base titrations, volumetric or coulometric, have been performed. The pH range investigated is 0.3–12. UV–vis spectra recorded at various pH values showed that the substitution pattern at the bicycle strongly affects the absorption and emission properties of the triazoles. Current/voltage curves recorded at various pH values also indicate that only a cationic monoprotonated species undergoes irreversible reduction at potential values spanning the range − 0.9 V to − 1.3 V (vs. Ag/AgCl), depending on the pH and on the substituent’s nature. Particularly, on the fused-ring N-rich bicycle, with pentafluorophenyl as electron withdrawing group, reduction takes place at a potential of 0.05 V higher than the analogue with aminophenyl electron donor group. The mononuclear complexes formation between Cu(II) and a triazolo–triazole compound has been also highlighted by UV–vis spectra and current/voltage curves recorded at 0.3 < pH < 6.