High and low molar mass 3-alkyl-1,4-pentazadienes. Synthesis and photolysis

High and low molar mass compounds containing the 3-alkyl-1,4-diarylpentazadiene group were synthesized in the reaction of aromatic diazonium salts with primary amines. These high nitrogen compounds are characterised by high photosensitivity and thermostability. The photolytic decomposition was studied in detail with respect to the substitution at the aromatic moieties and at N-3 of the pentazadiene chromophore. Electron donating aromatic substituents were found to increase photosensitivity and decrease thermostability whereas electron withdrawing aromatic substituents cause higher photolytic and thermolytic stability. A little influence of the alkyl group at N-3 on the photosensitivity of the pentazadiene group was observed. Photolysis was investigated by means of UV/Vis spectroscopy and obeys first order kinetics for some compounds under investigation. Gel permeation chromatography (GPC) measurements during photolysis of pentazadiene polymers prove that irradiation with UV light causes irreversible chain degradation. Thermolysis in bulk was studied for all compounds by differential scanning calorimetry (DSC). In contrast to the results of the photolysis the alkyl substituent at N-3 has an effect on the thermostability of the pentazadiene chromophore.