Synthesis and absorption characteristics of two infrared cyanine dyes

Two infrared dyes, 1, 3, 3, 1′, 3′, 3′-hexamethylindotricarbocyanine iodide (A) and 1, 3, 3, 1′, 3′, 3′-hexamethyl-11-chloro-10, 12-propylenetricarbocyanine iodide (B), were synthesized and characterized by melting point, elemental analysis, IR, and IH-NMR. Their electron absorption spectra, laser absorption characteristics and solubility were investigated. The results showed that A and 8 have maximum absorption peaks at around 748 nm and 774 nm, respectivey, which match well with the wavelength output of the near infrared laser diode. The dyes were found to have photoinduced fading during irradiation with the infrared laser, especially in the presence of oxygen. However, this procession can be greatly slowed by using a layer of poly (vinyl alcohol) to barricade the dyes from oxygen. The experiments also showed that the dyes were thermally stable but decayed under strong sunlight. Furthermore, they are easily dissolved in some common solvents.