Pyridone based binary and ternary monomethine dyes derived from 2-amino-4-chloro-5-formylthiophene-3-carbonitrile

Abstract New monomethine dyes have been prepared by a simple and highly efficient method in acetic anhydride, in which the common pyridine-2,6-dione moiety and thiophene derivatives occupy each side of the methine unit. Among them, the ternary monomethine-azo dyes were first obtained by the particularly useful post-modification synthetic strategy, in order to further adjust the π -conjugated system and electronic spectra of 2-amino-3-cyano-4-chloro-5-formylthiophene based heterocyclic hydrazone/azo dyes. UV−Vis spectral analyses reveal that the synthesized heterocyclic dyes exhibit a large color gamut because of the extension of the conjugation length of the chromophore, where the maximum absorption wavelength ( λ max ) is significantly red-shifted up to 181 nm from binary monomethine to ternary monomethine-azo dyes.