Original scientific paper

Electronic Absorption Spectra of New y-Keto-dimethine Cyanine Dyes and Apocyanines

A. I. M. Koraiem ; Chemistry Department, Aswan-Faculty of Science, Aswan, Egypt
M. M. Girgis ; Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt
Z. H. Khalil ; Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt
R. M. Abu El- Hamd ; Chemistry Department, Aswan-Faculty of Science, Aswan, Egypt

Abstract

New asymmetrical y-keto-dimethine cyanines (2.-f) were prepared through the condensation of phenyl glycosal derivatives (l.-e) with 2-methyl pyridinium (quinolinium)- 2yl salts. Such dyes were converted into the corresponding dyes (3a-g and 4a-d) by cyclocondensation with hydrazines or hydroxylamine hydrochloride under suitable conditions. The new synthesized cyanines were identified by elemental and spectral analyses. The U'V-visible absorption spectra of some selected dyes were investigated in pure and mixed solvents as well as in aqueous buffer solutions. Molecular complex formation with ethanol was verified by mixed solvent studies. Electronic transitions were attributed to either locally excited or predominantly charge
transfer states. The spectral shifts were discussed in relation to molecular structure and in terms of medium effects. The variation of absorbance with pR was utilized for the determination of the pK. value for aselected compound (2e). The photostability of some selected đyes (2e, 3g and 4d) was investigated.

Keywords

Hrčak ID:

176516

URI

https://hrcak.srce.hr/176516

Publication date:

26.3.1991.

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