Synthesis, structure and solvatochromic properties of some novel 5-arylazo-6-hydroxy-4-(4-methoxyphenyl)-3-cyano-2-pyridone dyes: Hydrazone-azo tautomeric analysis

A series of eleven new 5-arylazo-6-hydroxy-4-(4-methoxyphenyl)-3-cyano-2-pyridone dyes was synthesized and their absorption spectra were recorded in twenty solvents in the range 300–600 nm. Different solvent parameters, such as microscopic solvent polarity, ETN, relative permittivity, εr, refractive index, n, the Kamlet–Taft and the Catalan parameters were used for the evaluation of the solute–solvent interactions and the solvatochromic shifts of the UV–vis absorption maxima of the hydrazone tautomeric form of the investigated arylazo pyridone dyes. The Catalan solvent scales are found to be the most suitable for describing the solvatochromic behavior of the dyes.