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Comparison of adsorption mechanism on colloidal silver surface of alafosfalin and its analogs
Author(s) -
Podstawka Edyta,
Andrzejak Marcin,
Kafarski Paweł,
Proniewicz Leonard M.
Publication year - 2008
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1977
Subject(s) - chemistry , raman spectroscopy , density functional theory , adsorption , molecule , analytical chemistry (journal) , absorption (acoustics) , raman scattering , infrared , crystallography , stereochemistry , computational chemistry , materials science , organic chemistry , composite material , physics , optics
This study reports the Raman (FT‐RS) and absorption infrared (FT‐IR) spectra, based on calculated wavenumbers and normal modes of vibrations, of the following compounds: L ‐Ala‐ L ‐NH‐CH(Me)‐PO 3 H 2 (alafosfalin, A1), L ‐Ala‐ D ‐NH‐CH(Me)‐PO 3 H 2 (A2), L ‐Ala‐ L ‐NH‐CH(Et)‐PO 3 H 2 (A3), D , L ‐Ala‐ D,L ‐NH‐CH(Et)‐PO 3 H 2 (A4), L ‐Ala‐ D ‐NH‐CH(iPr)‐PO 3 H 2 (A5), L ‐Ala‐ D,L ‐NH‐CH(iPr)‐PO 3 H 2 (A6), L ‐Ala‐ D,L ‐NH‐CH(tBu)‐PO 3 H 2 (A7), L ‐Ala‐ D,L ‐NH‐CH(iBu)‐PO 3 H 2 (A8), L ‐Ala‐ D,L ‐NH‐CH(cBu)‐PO 3 H 2 (A9), L ‐Ala‐ D,L ‐NH‐CH(nPA)‐PO 3 H 2 (A10), β‐Ala‐ D ‐NH‐CH(Me)‐PO 3 H 2 (A11), and D,L ‐Ala‐NH‐C(Me,Me)‐PO 3 H 2 (A12). The equilibrium geometries and vibrational wavenumbers are calculated using density functional theory (DFT) at the B3LYP; 6–31 + + G** level of theory using Gaussian'03, GaussSum 0.8, and GAR2PED software. We briefly compare and analyze the experimental and calculated vibrational wavenumbers in the range of 3600–400 cm −1 . In addition, Raman wavenumbers are compared to those from surface‐enhanced Raman scattering (SERS) for the phosphonodipeptides of alanine (Ala) adsorbed on a colloidal silver surface. The geometry of these molecules etched on the silver surface is deduce from the observed changes in both the intensity and breadth of Raman bands in the spectra of the bound vs free species. For example, A7, A8, A1, A3, and A4 appear to adsorb onto the colloidal silver particles mainly through the phosphonate terminus, and for A3 and A4, through the C‐NH 2 and CONH fragments. The most dominant SERS bands of A5, A6, A9, A10, and A11 are due to the amide bond vibrations, as well as to the vibrations of the C‐NH 2 group (A9 and A10) and the CC group (A6 and A11). The differences recorded for the A5, A6, A9, A10, and A11 and those of A2 and A12 are due to interactions between the amine and methyl groups with the silver surface, and they reflect vibrational characteristic of these groups. Copyright © 2008 John Wiley & Sons, Ltd.