Synthesis of dyes containing fluorine atoms in the polymethine chain

Abstract

1. The condensation of α-fluoro-β-dimethylaminoacrolein aminal with ketones, β-dicarbonyl compounds, and CH-acids was investigated. 2. The synthesized dimethylamino-γ-fluorodienones (merocyanins) exist in the open form and are not cyclized to 2H-pyrans. 3. γ-Fluoro and γ,γ′-difluoroketocyanins were synthesized; their alkylation afforded alkoxynonamethine salts. Fluorine-containing thiapentacarbocyanin dyes were obtained from the latter compounds. 4. Dimethylammonium salts of tetracyano-γ-fluoropentadiene andγ-fluorotrimethinoxanine were synthesized. These compounds were used as the anionic components in obtaining cation-anion cyanin dyes. 5. The effect of the fluorine atom on the color of the synthesized dyes was investigated. It was shown that a fluorine atom in the polymethine chain behaves like an electron donor substituent. However, in sterically hindered merocyanins it elicits a hypsochromic shift of the absorption band even at even positions of the polymethine chain.