Redox-initiated radical decomposition of triazenes and their platinum complexes studied by cyclic voltammetry and EPR spectroscopy

Abstract

Triazenes p-R¹–C₆H₄–NN–NR²R³(R¹= H, butyl, CH₃O, CN and NO₂, R²= CH₃, cyclohexyl, butyl or longer chains, R³= H, OH) are irreversibly cathodically reduced at –1.5 to –2.7 V (vs. saturated calomel electrode) and oxidised from 0.8 to 1.7 V. The reduction peak potentials became more negative and the first oxidation peak potentials less positive if R³ was OH. Using spin-trapping, radicals p-R¹–C₆H₄˙ and ˙R² were identified as fragmentation products in the electrolytic and peroxy-initiated decomposition of triazenes. Radicals p–R¹C₆H₄–NO˙–R², representing the oxidised cage products after N₂ elimination, were observed in the oxidation of triazenes with peroxy acid. An NO₂-centred radical anion was found in the cathodic reduction of a Pt complex with R¹= NO₂. The above specified decomposition route of triazenes is modified if these are coordinated in Pt complexes. The formation of radicals is discussed assuming two tautomeric forms of triazenes.