Resonance Raman spectra and excitation profiles of some rifamycins

Abstract

The resonance Raman Spectra of rifamycin SV, its sodium salt and rifampicin have been investigated under various physical conditions. The excitation profiles of the strongest Raman bands have been measured using an Ar+ laser for excitation. The proposed vibrational assignment indicates that the group is the main portion of the chromophore for both rifamycin SV Na salt and rifampicin molecules. Excitation profile studies of the 6(C-O-) and v(C-OH) vibrations indicate the presence of a single electronic transition in the visible region.In addition these two modes derive their intensities from 0-1 vibromic transitions whereas no evidence for the contribution due to the 0-0 term is found. This is explained in terms of coupling with the other totally symmetric modes and broadening due to phonowlectron interactions.

The influence of pH and anions on the adsorption mechanism of rifampicin on silver colloids

“…In the pH range 12.6-4.0 the absorption spectrum for 10 5 M rifampicin is invariant, whereas at pH Ä 2.6 considerable changes are evident. The bands in this wavenumber range are primarily due to the ring-stretching modes of the chromophore, 9,17 suggesting a variation in the chromophore structure at acidic pH. Ł transitions of the chromophore.…”

Rifampicin adsorbed onto magnetite nanoparticle: SERS study and insight on the molecular arrangement and light effect

“…In addition, while comparing with the free RIF molecule, the SERS spectrum of the MFBL/RIF sample shows the onset of five new bands at 527, 571, 762, 1353, and 1390 cm −1 . The SERS bands found at 571 and 1353 cm −1 are, respectively, assigned to the vibrational modes δ (C–OH) and ν (C–OH), whereas the bands peaking at 527, 762, and 1390 cm −1 are associated to the ring's vibrational modes, namely, δ (C–C) and ν (C–C) . Furthermore, while adsorbed onto the magnetite nanoparticle's surface, the RIF molecule's SERS bands associated with the δ (C–O − ) at 466 cm −1 , δ (C=O) at 496 cm −1 and ring stretching modes at 1435 and 1509 cm −1 are quenched .…”

“…The explanation for the onset of the SERS bands at 527, 762, and 1390 cm −1 and the quenching of the SERS bands at 1435 and 1509 cm −1 in the spectra of the MFBL/RIF sample are not clear yet. However, drawing an analogy with the naphthalene molecule, it could be proposed that these bands are associated with the in‐plane ring stretching mode of the naphthohydroquinone chromophore . More specifically, the onset vibrational modes present A 1g symmetry, whereas the quenching vibrational modes present B 1u and B 2u symmetries.…”

“…The SERS bands found at 571 and 1353 cm À1 are, respectively, assigned to the vibrational modes δ(C-OH) and ν(C-OH), whereas the bands peaking at 527, 762, and 1390 cm À1 are associated to the ring's vibrational modes, namely, δ(C-C) and ν(C-C). [1,29] Furthermore, while adsorbed onto the magnetite nanoparticle's surface, the RIF molecule's SERS bands associated with the δ(C-O À ) at 466 cm À1 , δ(C=O) at 496 cm À1 and ring stretching modes at 1435 and 1509 cm À1 are quenched. [1,29] Finally, it is also observed (Fig.…”

The adsorption of rifampicin on gold or silver surfaces mediated by 2-mercaptoethanol investigated by surface-enhanced Raman scattering spectroscopy

“…The biological activity of RP involves the inhibition of prokaryotic DNA-dependent RNA polymerases [19]. The resonance Raman (RR) spectra of RP with the corresponding excitation profiles and the surface-enhanced resonance Raman scattering (SERRS) spectra of RP, rifamycin and rifaximin with adsorption proposal based on the vibrational assignment are reported [20,21]. The influence of pH on the adsorption mechanism of RP on AgNP was studied by UV-VIS, RR and SERRS spectroscopies [22].…”