Raman, Infrared, and Surface-Enhanced Raman Spectroscopy in Combination with ab Initio and Density Functional Theory Calculations on 10-Isopropyl-10H-phenothiazine-5-oxide

Abstract

Raman, infrared, and surface-enhanced Raman spectroscopies were applied to the vibrational characterization of the most stable conformer of the 10-isopropyl-10H-phenothiazine-5-oxide derivative. To find the optimized structure and the computed vibrational wavenumbers of the title compound, ab initio calculations at the Hartree−Fock level of theory and density functional theory calculations at the BPW91 and B3LYP levels of theory were performed. The comparison of the surface-enhanced Raman (SER) spectra, obtained only on activated silver colloids, with the corresponding Raman spectra reveals small shifts (Δν ≤ 5 cm-1) and proves the partial chemisorption of the molecules on the silver surface via the lone pair electrons of the oxygen atom; the electromagnetic mechanism is the main mechanism of the enhancement. Variations of the SER spectra with the change of pH were attributed to the orientational changes of the adsorbed molecules with respect to the silver surface.

Probing the adsorption mechanism in thiamazole bound to the silver surface with Surface-enhanced Raman Scattering and DFT

“…The AEF for the respective Raman bands are shown in Table 2. The observed SERS enhancements for the thiolate Raman bands are of the order of 10 5 -10 6 .…”

“…An important aspect of SERS is its potential in probing the interaction between various adsorbates and metallic surfaces [3][4][5][6][7][8][9][10][11][12][13][14]. Application of the 'surface selection rules' [15,16] provides information on the sites of binding and the molecular orientation on the metal surface.…”

Surface enhanced Raman scattering (SERS)—a quantitative analytical tool?

“…8 Theoretical methods used to explain Raman spectra only partly explain the SERS spectra. 9 This is due to the complicated mechanisms responsible for the excitation of the scattering process.…”

Influence of Temperature on the Rotameric Forms of the Propyl Acetate Molecule: Raman and FTIR Spectroscopic Studies Aided by ab Initio and Car–Parrinello Molecular Dynamics Simulations

“…17−21 Despite this fact, one can see that the positions of the peaks between the experimental and the calculated spectra are in harmony. 22,23 The intensity profiles showing the differences between the experimentally observed and theoretically simulated Raman bands are shown in Figure S3 of the Supporting Information. The relative populations of TT, TG + , G + T, and G + G − forms are estimated using the relation…”