A Green and Practical Approach to Chromenylium–Cyanine Dye Synthesis Using Triethylammonium Hydrogen Sulfate as an Alternative to Acetic Anhydride
Abstract
Chromenylium-cyanine dyes have attracted considerable attention in recent years due to their strong absorption and emission characteristics in the near-infrared (NIR) region, which make them highly promising candidates for the development of advanced optical sensors, bioimaging agents, and molecular probes. The synthetic methodologies traditionally employed for the preparation of such dyes typically rely on reaction media such as acetic anhydride. Although acetic anhydride is effective in facilitating key condensation reactions, it poses significant limitations. Specifically, acetic anhydride is highly volatile, flammable, and toxic, and its use requires strict safety precautions. Furthermore, regulatory restrictions on its availability in certain countries highlight the growing need to identify more sustainable and environmentally benign alternatives in accordance with the principles of green chemistry. In light of these challenges, the present study explores the use of triethylammonium hydrogen sulfate (TEAHS) as a greener and safer reaction medium in the synthesis of a novel chromenylium-cyanine dye. Under optimized conditions, the target compound (CS2) was successfully synthesized through the condensation reaction of 2 with 3 in the presence of TEAHS. The resulting dye exhibits characteristic chromenylium-cyanine optical properties, and its structure was unequivocally elucidated using advanced two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy for the first time in the literature.
Keywords
characterization , chromenylium-cyanine , green chemistry , TEAHS
Kaynakça
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