Photofading of Azo Pyridone Dyes in Solution

Abstract

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

Prediction of the photofading of 1‐H or 1‐ethyl derivatives of 3‐cyano‐6‐hydroxy‐4‐methyl‐5‐(p‐X‐phenylazo)‐2‐pyridone dyes and their azo‐hydrazone tautomerism: A theoretical study

“…The reaction mechanism of oxidation of C=C bonds using MINDO/3 method with singlet oxygen is described by Dewar and Thiele 50 and by other authors. 17,51,52 In the calculations of dye properties in its gaseous form by the MO method, the dyes are not associated, and their photochemical degradation is much faster than the physical disintegration of the fibre. Hence, the disintegration factor may be ignored without much risk of an error in calculations.…”

“…Hence, the disintegration factor may be ignored without much risk of an error in calculations. 17,36 The conducted calculation research shows the electron density calculations of orbitals in the ground HOMO and the excited LUMO energy level of the dye. Frontier molecular orbital theory suggests that the area of high electron density in the HOMO of the dye is the site of the singlet oxygen 1 O 2 electrophilic attack.…”

“…9,14 Additionally, the density functional theory (DFT) calculations of the investigated derivatives of azo dyes are applied by some researchers. 3,[14][15][16][17][18] In theory, the azo dyes derived from pyridone may exist in several tautomeric forms, with a predominance of the hydrazone form. 12,19,20 The success of pyridone dyes is due to the simplicity of their synthesis, ability to be coupled with many diazo compounds, high molar extinction coefficients, and relatively high lightfastness.…”

Optimization of electrochemical decolorization of certain arylazo pyridone dyes

“…It was established that the photofading rate increases with increasing solvation of the dyes, as well as in the presence of two electron-withdrawing substituents (NO 2 and Cl) on the benzene ring. 9 The same authors also studied the photostability of 3-(mono-and di-substituted arylazo)-5-cyano-2-hydroxy-4-methyl-6--pyridones in N,N-dimethylformamide under 254 nm light. It was found that the simultaneous presence of two electron-withdrawing substituents in the diazo component of the dyes caused an increase in the fading rate, while the introduction of an hydroxyalkyl group to the coupling component resulted in a decrease in the fading rate.…”

Synthesis, structure and solvatochromism of new 5-(4-substituted phenylazo)-4-(4-substituted phenyl)-6-hydroxy-3-cyano-2-pyridones

“…It was established that a fair linear correlation existed between the observed rate constant and the free energies of transfer, suggesting the possibility that the photofading rate increased with increasing solvation of dyes. The rate was increased by the presence of two electron-withdrawing substituents (NO 2 and Cl) on the benzene ring [77]. The same authors have also studied photostability of 3-(mono-and di-substituted arylazo)-5-cyano-2-hydroxy-4-methyl-6-pyridones in N,Ndimethylformamide.…”