Resonance Raman spectral studies on the vibrational frequencies of some azo dyes in the solid state and in alkaline solution

Abstract

Resonance Raman spectra of two azo dyes, 2-hydroxy-2′-carboxy-5-methylazobenzene and 2-hdroxy-2′-carboxy-5-methoxyazobenzene, in the solid state and in 0.1 M NaOH solution were investigated. For comparison, their infrared absorption spectra were also recorded in the solid state and in solution in chloroform. Characterization of the Bands in the Raman spectra of the alkaline solution and their assignments to different hybridized modes were made on the basis of the deprotonated azo and quinonoid molecular forms (in resonance) in alkaline solution.