The influence of various substituent groups on the absorption spectra and photostability of some azo pyridone dyes has been examined in N,N-dimethyl-formamide.On exposure to a spectrum of ultraviolet radiation, photoreduction is mostly caused by radiation of 254 nm. The primary photochemical reaction with azo pyridone dyes involves hydrogen abstraction from the amide solvent. Two electron-withdrawing substituents in the diazo component of azo pyridone dye exert a bathochromic effect and increase the fading rate, while introduction of an alkylol group to the coupling component results in hypsochromic shifts and a decrease in the fading rate.
We report on the investigation and kinetic measurements of the photofading process of some o-, p -substituted azo pyridone dyes in formamide, N,N-dimethylformamide, and N,N'-dimethylacetamide. The free energies of solvation of dyes in the three solvents have been calculated by measuring the distribution coefficients of the dyes between the amide solvent and n-hexane as the immiscible standard solvent. A fair linear
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