SURFACE-ENHANCED RAMAN-SPECTROSCOPIC INVESTIGATIONS OF THIAZOLE ORANGE DERIVATIVES USING VISIBLE AND NEAR-INFRARED EXCITATION

Surface-enhanced Raman spectra of the two thiazole orange derivatives, TO6 {1-(N,N'-tetramethyl-1,3- hydro(benzo-1,3-thiazole)-2-methylidene ]quinolnium triiodide} and TOTO 4,4,8,8-tetramethyl-4,8-diazaundecamet hylene)-bis- 4-[3-methyl-2,3-dihydro(benzo-1,3-thiazole)- 2- methylide ne]quinoliniumtetraiodide}, were recorded with visible (457.9 and 514. 5 nm) and near-infrared (1064 nm) excitation on silver colloids. The s pectra were compared with the corresponding non-enhanced Raman spectra obtained in the near-infrared region and the resonance Raman spectra obtained with visible excitation. The qualitative enhancement pattern is explained within the electromagnetic theories. Partial assignment o f the vibrational wavenumbers was achieved by comparison of observed b and positions and intensities in the IR and Raman spectra with wavenum bers and intensities from quantum chemical calculations. Information o n the adsorption geometry at the silver surface can be obtained on bas is of this assignment. The surface-enhanced Raman spectrum of TOTO on gold colloids was recorded with 1064 nm excitation and compared with t he corresponding spectra on silver colloids.