Investigation of Optical and Solution Properties of Azo-dyes Derived from Ethylacetoacetate and Aromatic Amines

Rotamerism and tautomerism are phenomena being considered as processes of isomerization and proton exchanging between two or more forms, respectively leading to rearrangement of electronic density in whole molecule and therefore, to significant change in spectral and photophysical behavior [1, 2]. Individual rotamers and tautomers can exist in various isomeric forms differing in type of intramolecular hydrogen bonding [3, 4]. Existence of rotameric transformation in azo-hydrazone forms of azo dyes derived from β-dicarbonyl compounds is an interesting example of molecular switching [5]. In this work a series of azo dyes synthesized from benzenoeid aromatic amines and a β-keto-ester were firstly fully characterized by spectroscopic techiques, IR, NMR, and Mass. Due to switchable properties of the synthesized dyes, the effects of thesubstituents on rotameric equilibrium in solution along with solid state were investigated by Hammet correlation parameters based on their spectroscopic data, UV-vis, IR and NMR spectra, as well as electrochemical properties. Finally, theoretical calculations were carried out to determine the energy barrier of rotameric transformation in gas phase alongside HOMO-LUMO band gas