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Synthesis of symetrical near-infrared dyes containing benzo[c,d]indole system
Abstract
Five symmetrical near infrared dyes having different linker between the two heterocycles were synthesized by condensation of N-alkylbenzo[c,d]indolium salts with either squaric acid or imine. All synthesized dyes showed strong absorbance in the near-infrared region of 850-1015 nm and can be used as nucleic acid detection or fluorescent labeling agents for proteins. Three of the dyes 21, 22 and 25 containing functionalized N-substituents (ester group) can be further modified or covalently attached to target. The structures of these cyanine dyes where characterized by virtue of NMR, UV, MALDI and Elemental analysis.
Keywords: Synthesis, cyanine, Polymethine dyes, Near-IR dyes, Absorption, Chromophore.