@phdthesis{Pavel2003,
  author    = {Pavel, Ioana-Emilia},
  title     = {Vibrational spectroscopy and density functional theory calculations, a powerful approach for the characterization of pharmaceuticals and new organometallic complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-7186},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2003},
  abstract  = {In the current work, several well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) and new organometallic compounds (nickel(II) cupferronato complexes NiL2An, L = PhN2O2-, n = 1, A = o-phenanthroline (1), o,o'-bipyridine (2) and n = 2, A = H2O (3), o-NH2Py (4), o-C6H4(NH2)2 (5); silylene-bridged dinuclear iron complexes [Cp(OC)2Fe]2SiX2 (X = H (6), F (7), Cl (8), Br (9), I (10)); 3-silaoxetane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-oxa-3-silacyclobutane (11) and 3-silathietane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-sila-3-thiacyclobutane (12) compounds), which have successfully been characterized by using vibrational spectroscopy in conjunction with accurate density functional theory (DFT) calculations, are presented. The DFT computed molecular geometries of the species of interest reproduced the crystal structure data very well and in conjunction with IR and Raman measurements helped us to clarify the structures of the compounds, for which no experimental data were available; and this, especially for the new organometallic compounds, where the X-Ray analysis was limited by the non-availability of single crystals (3, 5, 10). Furthermore, a natural population analysis (NPA) and natural bond orbital (NBO) calculations together with a detailed analysis of the IR and Raman experimental as well as calculated spectra of the new organometallic compounds, allowed us to study some special bonding situations (1-12) or to monitor the structural changes observed with the change in temperature during the Raman experiments (11, 12). By combining these two methods (DFT and vibrational spectroscopy), the auspicious results obtained on the organometallic compounds 6-12 and overall in literature, made us confident of the power of theoretical calculations in aiding the interpretation of rich SERS spectra by solving some interesting issues. Consequently, the Raman and SERS spectra of well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) or new potentially biological active organometallic complexes (1-5), that were synthetized by our coworkers, were discussed with the assistance of the accurate results obtained from DFT calculations (structural parameters, harmonic vibrational wavenumbers, Raman scattering activities), and many previous incomplete assignments have been analyzed and improved. This allowed us to establish the vibrational behavior of these biological compounds near a biological artificial model at different pH values or concentrations (Ag substrate), taking into account that information about the species present under particular conditions could be of great importance for the interpretation of biochemical processes. The total electron density of molecules and the partial charges situated on selected atoms, which were determined theoretically by NPA, allowed us to establish the probability of different atoms acting as an adsorptive site for the metal surface. Moreover, a closer examination of the calculated orbitals of molecules brought further arguments on the presence or absence of the photoproducts at the Ag surface during the irradiation (1,4-dihydrazinophthalazine sulfate). Overall, the results provide a benchmark illustration of the virtues of DFT in aiding the interpretation of rich vibrational spectra attainable for larger polyatomic adsorbates by using SERS, as well as in furnishing detailed insight into the relation between the vibrational properties and the nature of the Ag substrate-adsorbate bonding. Therefore, we strongly believe that theoretical calculations will become a matter of rapidly growing scientific and practical interest in SERS.},
  subject      = {Arzneimittel},
  language  = {en}
}