Structure and Spectroscopic Studies of Bis Azo Compounds with S/SO2 Bridges and Containing Cyclic-1,3-Dicarbonyl Groups

Abstract

A series of new bis azo dyes were synthesized starting from aromatic diamine with S/SO2 bridges and cyclic-1,3-dicarbonyl groups; contain active methylene group, namely; 3,3-dimethyl-1,5-cyclohexadione (dimedone), 1,3-cyclohexadione and 2,2-dimethyl-1,3-dioxane-4,6-dione to give 1-6. Whether the reaction is complete and the purity of the compounds were checked with TLC. The structure of the newly synthezed compounds was investigated by using, FT-IR, 1HNMR, LC–MS/MS and UV–Visible spectrophotometric methods, CH3OH was used in the LC-MS/MS experiments, and the molecular masses of the compounds were seen as M and M+1 protonated in the spectrum. In the UV-Vis spectra of these compounds, the solvent effect by using different solvents and also the acid-base effect by adding HCl or KOH to the medium were investigated. The tautomeric equilibrium forms (enol-imine O-H….N, keto-amine O….H-N forms) of the compounds were investigated according to the electronic spectrum recorded in chloroform, dimethylformamide (DMF), acetic acid, and methanol solvents. The results of the UV-visible and 1H-NMR spectra indicated that the compounds in chloroform, dimethylformamide (DMF), acetic acid and methanol were found in the hydrazo tautomer (keto-amine O….H-N forms) of the proposed tautomeric forms.