Synthesis and spectral properties of novel hemicyanine dyes

Novel hemi- and azahemicyanine dyes were obtained from 5,11-dioxobenzo[2,3-b;2′,3′-b′]bis-pyrazolo[4,5-b]-(1,4-oxazinium, 1,4-thiazinium, and pyrazinium) diiodides. For all synthesized cyanine dyes, the structure-color relationship was studied in 95% EtOH. For selected cyanine dyes, solvatochromism and halochromism were found in pure solvents with different polarities and in aqueous universal buffer solutions with different pH values, respectively. Positive and negative structure-color correlations, solvatochromism, and halochromism were observed. Structures of the synthesized dyes were established based on elemental analysis, IR spectroscopy, UV-VIS spectroscopy, and 1H NMR spectroscopy.