Solvent and structural effects on the spectral shifts of 5-(substitutedphenylazo)-3-cyano-6-hydroxy-1-(2-hydroxyethyl)-4-methyl-2-pyridones

Abstract

Spectral properties, solvatochromism and azo-hydrazone tautomerism of ten 5-(substituted phenylazo)-3-cyano-6-hydroxy-1-(2-hydroxyethyl)-4-methyl-2-pyridones in twenty-two solvents are investigated.For quantitative evaluation of the solvent effects on the UV-vis absorption maxima, the principles of the linear solvation energy relationships are used, i.e. models proposed by Kamlet-Taft and Catalán. Linear free energy relationships are applied to the UV-vis absorption spectra and correlation of absorp-tion frequencies with Hammett substituent constants are performed. Furthermore, the influence of the electronic nature of the substituents on1H and13C NMR shifts is investigated by simple and extended Hammett equations, as well as by Swain-Lupton equation.