Heptamethine and nonamethine cyanine dyes: novel synthetic strategy, electronic transitions, solvatochromic and halochromic evaluation

Hassan A. Shindy, Mohamed A. El-Maghraby, Maha M. Goma and Nemat A. Harb

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New polymethine cyanine dyes covering heptamethine cyanine dyes (tricarbocyanine dyes) and nonamethine cyanine dyes (tetracarbocyanine dyes) derived from the nucleus benzo[(2,3-b)benzoxazine; (2',3'-b')furo (3,2- d)pyrazole] were designed and prepared using novel synthetic strategy. Electronic transitions for all the synthesized cyanine dyes was determined and evaluated through investigating their electronic visible absorption spectra in 95% ethanol solution. The dyes were thought to be better electronic transitions when they absorb light at higher wavelength bands (bathochromic shifted and/or red shifted dyes). Consequently, the electronic transitions of the dyes decreases when they absorb light at lower wavelength bands (hypsochromic shifted and/or blue shifted dyes). Solvatochromic and/or halochromic evaluation for some selected dyes was carried out and determined through examining their electronic visible absorption spectra in 6 (six) pure solvents having different polarities [water (78.54), dimethylformamide (36.70), ethanol (24.3), chloroform (4.806), carbontetrachloride (2.238) and dioxane (2.209)] and/or in 8 (eight) aqueous universal buffer solutions owing varied pH values (1.99, 2.99, 4.30, 6.87, 7.96, 8.91, 10.55 and 12.04 units), respectively. Structural characterization and determination was carried out via elemental analysis, visible, mass, IR and 1HNMR spectroscopic data.