Jochen Dipl Chem Dr Dauth

The photochemical decomposition of azo compounds (a spin trap study)

Abstract The radical products formed in the photochemical decomposition of azo compounds (R 1 N 2 R 2 ) dissolved in various solvents were investigated. Nitrosodurene, 2-methyl-2-nitroso-propane and 5,5-dimethyl-1-pyrroline- N -oxide (DMPO) were used as spin traps. In the first group of azo compounds, in which R 1 was X-substituted phenyl and R 2 was SO 3 Na or SO 2 Ph, the spin adducts of R 1 and R 2 were observed. In the second group of azo compounds (R 1 = R 2 = R, where R was a tertiary-substituted carbon), the carbon-centred radicals R . were formed and trapped if irradiated in an argon atmosphere. When irradiated in air, the initially formed radicals R . were converted to oxygen-centred radicals (presumably peroxy or alkoxy) and trapped by DMPO; . OH radicals were also observed as further intermediates.

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

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.