Synthesis and spectral properties of novel series of fluorene-based azo dyes containing thiazole scaffold: Studying of the solvent and substituent effect on absorption spectra

Abstract

A novel series of new 2-arylazo-thiazole dyes pendant to fluorene moiety was synthesized. The novel azodyes have been accessed via the reaction of hydrazonoyl halides with the 2-(9H-fluoren-9-ylidene)hydrazine-1-carbothioamide in a simple manner using mild reaction conditions. The structures of the synthesized dyes were elucidated by spectroscopic tools and elemental analyses. The UV visible spectra of the newly synthesized arylazo dyes were recorded in nine different solvents in the region of 300–800 nm. Solvent and substituents effect, as well as the influence of the addition of acid and base on the absorption frequencies of arylazo thiazoles were discussed. To achieve deep understanding about interactions between the synthesized dyes and solvent, Kamlet-Taft and Catalan model have been used for the evaluation of the solvatochromic shifts of the absorption maxima in UV–vis spectra of the azo-hydrazo tautomers of the arylazo thiazole dyes under investigation. The results revealed the great influence of solvent polarizability and hydrogen-bond acceptor basicity parameters in the absorption frequency shifts of the selected synthesized arylazo dyes. The azo-hydrazo tautomeric form was found to depend on the substituents, solvent as well as when varying pH.