ELECTRONIC-SPECTRA OF SOME NEW SYNTHESIZED METHINE CYANINE DYES

New methine cyanine dyes such as monomethine (3a-e), azamethine (4a-c) and trimethine (6a-i) and (8a-c) incorporating a fused pyrazolo [3,4-d] oxazole nucleus were prepared. The new synthesised cyanines were identified by elemental and spectral analyses. The 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. The variation of absorbance with pH was utilized for the determination of the pKa values for selected compounds.