The structure of benzimidazole cyanine dyes, their spectroscopy and their performance in photographic emulsions

The multi-step synthesis of two benzimidazole trimethine cyanines as possible green sensitizing dyes (Gs3-1, Gs3-2) is reported. Compounds were characterized from UV-Vis, mass spectroscopic and NMR data. The charge density distributions of the two compounds, calculated using the semi-empirical MOPAC 93 package, are in agreement with assignments in NMR spectroscopy. Sensitizing properties of the cyanine dyes were evaluated in actual photographic T-grain emulsions.