Synthesis, characterization and spectroscopic properties of some new azo disperse dyes derived from 4-hydroxybenzo[h]quinolin-2-(1H)-one as a new synthesized enol type coupling component

4-Hydroxybenzo[h]quinolin-2-(1H)-one (IV) was synthesized from the cyclocondensation of 3-(naphthalen-1-ylamino)-3-oxopropanoic acid (I) or N,N′-di(naphthalen-1-yl)malonamide (II) and subsequently coupled with diazotized p-substituted aniline derivatives. The structures of the synthesized dyes were determined by spectroscopic and analytical methods. Solvent effects on the ultraviolet–visible absorption spectra of these novel azo dyes were studied in six pure organic solvents with different polarities. The color of the dyes is discussed with respect to the nature of substituents on the benzene ring. The tautomeric structures of the azo compounds were studied by 1H NMR spectroscopy in DMSO-d6 and CDCl3. The effects of acid and base on the visible absorption spectra of the dyes were also reported. Ionization constants, pKa, for these dyes were determined in 80 vol. % ethanol–water medium at room temperature and correlated with the substituent constant, σp.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► 4-Hydroxybenzo[h]quinolin-2-(1H)-one was synthesized. ► Some benzoquinolone based azo dyes were prepared. ► Tautomeric behavior and solvathochromic properties of the azo dyes were studied. ► Acidic dissociation constants were measured.