“…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.…”