Role of the bifurcated intramolecular hydrogen bond on the physico-chemical profile of the novel azo pyridone dyes

Abstract

A series of novel 5-(4-substituted phenylazo)-1-carboxymethyl-3-cyano-6-hydroxy-4-methyl-2-pyridones had been synthesized and characterized. The study includes spectral determination of the possible tautomeric forms and the intramolecular hydrogen bonding pattern. The influence of the bifurcated intramolecular hydrogen bond on the spectral properties has been discussed. The dyes exist in hydrazone form both solid state and in most of the employed solvents. Equilibrium between hydrazone and anion forms has been studied in N,N-dimethylformamide and N,N-dimethylacetamide. For quantitative elucidation of solvent effects on UV–Vis absorption maxima, a linear solvation energy relationship concept has been employed using Kamlet-Taft's and Catalán's equations. Antioxidative activity of the synthesized dyes has been chemically tested and two derivatives (hydroxy and methoxy) are qualified as promising antioxidant molecules.