The synthesis of new bis-azo dyes and spectroscopic investigation of their structures

In this study, novel bis azo compounds were synthesized from bis diazonium consisting of 4,4?-diaminodiphenyl skeleton which is connected with -O, -CH2-, -SO2 -groups via the coupling reactions of ß-hydroxynaphthalene, o-hydroxybenzaldehyde, o,p-dihydroxybenzaldehyde. The synthesized compounds are:Bis[4,4?-(2??-hydroxy-naphtylazo)]-diphenyl ether,Bis[4,4?-(4??-hydroxy-3??-formyl-phenylazo)]-diphenyl ether,Bis[4,4?-(2??, 4??-dihydroxy-3??-formyl-phenylazo)]-diphenyl ether,Bis[4,4?-(2??-hydroxy-naphtylazo)]-diphenyl sulphone,Bis[4,4?-(4??-hydroxy-3??-formyl-phenylazo)]-diphenyl sulphone,Bis[4,4?-(2??, 4??-dihydroxy-3??-formyl-phenylazo)]-diphenyl sulphone,Bis[4,4?-(2??-hydroxy-naphtylazo)]-diphenyl methane,Bis[4,4?-(4??-hydroxy-3??-formyl-phenylazo)]-diphenyl methane,Bis[4,4?-(2??, 4??-dihydroxy-3??-formyl-phenylazo)]-diphenyl methane.The structures of the compounds were characterized by FT-IR, 1H-NMR and 13C-NMR spectroscopy.In addition, the changes in the UV-vis absorption spectra of each compound were investigated with respect to the present functional groups in the structure and the polarity of the solvent used. The relationships between the functional groups and the solvent polarit versus absorption maxima were determined. Also, the color changes of the compounds in both acidic and basic media were examined in order to reveal the possibility of using these compounds as acid-base indicators.