Fourier transform Raman and surface‐enhanced Raman spectroscopy of some quinoline derivatives

Abstract

Fourier transform (FT) Raman and surface-enhanced Raman spectroscopy (SERS) were applied to the vibrational characterization of isoquinoline and 4-methylquinoline. The assignment of the vibrational modes was carried out on the basis of results obtained from density functional theory calculations. The comparison of SER spectra with the FT-Raman spectra reveals remarkable changes attributed to the chemical interaction between the molecules and the silver substrate. The SER spectra of the adsorbed molecules depend strongly on the pH conditions. Variation in SER spectra with change of pH is attributed to a change in orientation of the absorbed isoquinoline molecules with respect to the silver surface and to a change in the chemical nature of the 4-methylquinoline molecules.

Surface Raman characterization of cinchonidine-modified platinum in ethanol: effects of liquid-phase concentration and co-adsorbed hydrogen

“…g Consistent with published band assignments for 2,2 -biquinoline (see [61]). h Consistent with published band assignments for lepidine (see [62]). i Consistent with published band assignments for monosubstituted quinolines (see [63]).…”

Other Molecules with Pharmacological Activity

“…The characteristics of the SERS spectra at an alkaline pH reveal a partial chemisorption of lepidine molecules on the silver surface via the nonbonding electrons of the nitrogen, the band at 247 cm -1 proving this assumption (Bolboaca et al 2002). The bands assigned to the CC and CH stretching vibrations are also enhanced at these pH values.…”

“…Therefore, one can assume that the isoquinoline molecules are chemisorbed on the silver surface through the nonbonding electrons of the nitrogen atom (Bolboaca et al 2002). Thus, the bands that appear in the 1600−1400 cm -1 range are shifted to higher wavenumbers in the SERS spectra by 3−15 cm -1 .…”

“…The behavior of the adsorbed lepidine molecules denotes a partial chemisorption on the silver surface through the nonbonding electrons not only from the nitrogen atom but also from the ring (Bolboaca et al 2002). Thus, in the SERS spectrum at the pH value of 1, the bands that appear in the 1600−1400 cm -1 range are shifted to lower wavenumbers by 2−6 cm -1 , while in the SERS spectrum at pH = 14 these bands are shifted to higher wavenumbers by 1−5 cm -1 .…”

FT‐Raman and NIR‐SERS characterization of the antimalarial drugs chloroquine and mefloquine and their interaction with hematin

“…When the drug targets the nonchromophore part of the macromolecular structure, this information is unavailable using RR spectroscopy. In order to overcome this disadvantage, the use of SERS spectroscopy is the proper alternative, providing information about the adsorbed molecular species, 14,17,22 their functional groups involved in adsorption, the influence of the environmental pH conditions on adsorption, interaction between a specific drug and the target molecule upon adsorption on a proper surface, the mechanisms at the interface, etc.…”