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Electronic Spectra, Solvatochromic Behaviour, and Acidity Constants of Some New Azocoumarin Derivatives

N. M. Rageh, A. M. Abdel Mawgoud, and H. M. Mostafa

Department of Chemistry, Faculty of Science, Qena, South Valley University, Egypt


Abstract: The UV visible electronic spectra of some azocoumarin dyes derived from 6-aminocoumarin have been studied. The different bands observed have been assigned to the proper electronic transitions. The compounds exist mainly in the azo form but some of them exhibit an azo ⇌ hydrazone tautomeric equilibrium. Solvatochromic behaviour of these compounds was investigated by studying their visible spectra in pure and mixed organic solvents of different characters. The longest wavelength band displayed by the azocoumarin derivatives in DMF solution is assigned to an intermolecular CT transition. The solvated H-bonding complexes formed between DMF and 8-hydroxyquinoline derivatives were investigated. ∆G and Kf values of these complexes have been determined. The acidity constants of six compounds were determined from the spectra in aqueous-ethanolic solutions of varying pH values.

Full paper in Portable Document Format: 532a107.pdf


Chemical Papers 53 (2) 107–113 (1999)

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