SPONTANEOUS RAMAN-SPECTRA OF THE CYANINE DYE DODCI AND ITS 6 ANALOGS USING TITANIUM-SAPPHIRE LASER EXCITATION

The infrared and spontaneous Raman spectra of the cyanine dye 3,3-diethyloxadicarbocyanine iodide (DODCI) and its six analogues, 3,3'-diethylthiacarbocyanine iodide (DTCI), 3,3'-diethyl-9-methylthiacarbocyanine iodide (MDTCI), 3,3'-diethylthiadicarbocyanine iodide (DTDCI), 3,3'-diethylselenacarbocyanine iodide (DSCI), 3,3'-diethyloxacarbocyanine iodide (DOCI), and 3,3'-diethyloxatricarbocyanine iodide (DOTCI), have been measured. A Raman spectrometer consisting of a Ti:sapphire laser and a CCD detector was found to be advantageous in avoiding the strong fluorescence of these cyanine dyes. The spectra have been compared, and several of the vibrational bands have been assigned. The locations of the CC and CN stretching vibrations suggest considerably weakened bond alternations for these molecules in solution.