SERS investigation on five-membered heterocyclic compounds: isoxazole, oxazole and thiazole (original) (raw)
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Journal of Physical Chemistry B, 2009
Surface-enhanced Raman scattering (SERS) spectra from phosphonate derivatives of N-heterocyclic aromatic compounds immobilized on an electrochemically roughened silver electrode surface are reported and compared to Raman spectra of the corresponding solid species. The tested compounds contain imidazole [ImMeP ([hydroxy-(1H-imidazol-5-yl)-methyl]-phosphonic acid) and (ImMe) 2 P (bis[hydroxy-(1H-imidazol-4-yl)methyl]-phosphinic acid)]; thiazole [BAThMeP ((butylamino-thiazol-2-yl-methyl)-phosphonic acid) and BzAThMeP ((benzylamino-thiazol-2-yl-methyl)-phosphonic acid)]; and pyridine ((PyMe) 2 P (bis[(hydroxypyridin-3-yl-methyl)]-phosphinic acid) aromatic rings. Changes in wavenumber, broadness, and the enhancement of N-heterocyclic aromatic ring bands upon adsorption are consistent with the adsorption primarily occurring through the N lone pair of electrons with the ring arranged in a largely edge-on manner for ImMeP and BzAThMeP or in a slightly inclined orientation to the silver electrode surface at an intermediate angle from the surface normal for (ImMe) 2 P, BAThMeP, and (PyMe) 2 P. A strong enhancement of a roughly 1500 cm-1 SERS signal for ImMeP and (PyMe) 2 P is also observed. This phenomenon is attributed to the formation of a localized CdC bond, which is accompanied by a decrease in the ring-surface π-electrons' overlap. In addition, more intense SERS bands due to the benzene ring in BzAThMeP are observed than those observed for the thiazole ring, which suggests a preferential adsorption of benzene. Some interaction of a phosphonate unit is also suggested but with moderate strength between biomolecules. The strength of the PdO coordination to the silver electrode is highest for ImMeP but lowest for BzAThMeP. For all studied biomolecules, the contribution of the structural components to their ability to interact with their receptors was correlated with the SERS patterns.
IR, Raman and SERS spectra of 2-phenoxymethylbenzothiazole
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
The FT-IR and FT-Raman spectra of 2-phenoxymethylbenzothiazole were recorded and analyzed. The surface enhanced Raman scattering (SERS) spectrum was recorded in a silver colloid. The vibrational wavenumbers of the compound have been computed using the Hartree-Fock/6-31G* basis and compared with the experimental values. The appearance of the AgO stretching mode at 237 cm −1 in the SERS spectrum along with theoretically calculated atomic charge density, leads us to suggest that the molecule is adsorbed through the oxygen atom with the molecular plane tilted on the colloidal silver surface. The direction of charge transfer contribution to SERS has been discussed from the frontier orbital theory.
J. Phys. Chem.B, 113, 10035-10042 (2009).pdf
Surface-enhanced Raman scattering (SERS) spectra from phosphonate derivatives of N-heterocyclic aromatic compounds immobilized on an electrochemically roughened silver electrode surface are reported and compared to Raman spectra of the corresponding solid species. The tested compounds contain imidazole [ImMeP ([hydroxy-(1H-imidazol-5-yl)-methyl]-phosphonic acid) and (ImMe) 2 P (bis[hydroxy-(1H-imidazol-4-yl)methyl]-phosphinic acid)]; thiazole [BAThMeP ((butylamino-thiazol-2-yl-methyl)-phosphonic acid) and BzAThMeP ((benzylamino-thiazol-2-yl-methyl)-phosphonic acid)]; and pyridine ((PyMe) 2 P (bis[(hydroxypyridin-3-yl-methyl)]-phosphinic acid) aromatic rings. Changes in wavenumber, broadness, and the enhancement of N-heterocyclic aromatic ring bands upon adsorption are consistent with the adsorption primarily occurring through the N lone pair of electrons with the ring arranged in a largely edge-on manner for ImMeP and BzAThMeP or in a slightly inclined orientation to the silver electrode surface at an intermediate angle from the surface normal for (ImMe) 2 P, BAThMeP, and (PyMe) 2 P. A strong enhancement of a roughly 1500 cm -1 SERS signal for ImMeP and (PyMe) 2 P is also observed. This phenomenon is attributed to the formation of a localized CdC bond, which is accompanied by a decrease in the ring-surface π-electrons' overlap. In addition, more intense SERS bands due to the benzene ring in BzAThMeP are observed than those observed for the thiazole ring, which suggests a preferential adsorption of benzene. Some interaction of a phosphonate unit is also suggested but with moderate strength between biomolecules. The strength of the PdO coordination to the silver electrode is highest for ImMeP but lowest for BzAThMeP.
SERS intensities of benzodiazines adsorbed on silver nanoparticles
2003
SERS excitation profiles of benzodiazines adsorbed on silver sols have been investigated and related to the surface plasmon resonances in the UV -Visible absorption spectra. Despite the existence of metal -ligand chemical bonds, evidenced by the occurrence of strong Ag -N stretching modes, spectral data can be interpreted in terms of enhancement due to the electromagnetic mechanism. q
The Journal of Physical Chemistry C, 2007
Surface enhanced Raman scattering (SERS) in silver nanocolloids and normal Raman spectra (NRS) in the bulk and in aqueous solution of 4-methyl-4H-1,2,4-triazole-3-thiol (4-MTTL) have been investigated. The observed Raman bands along with the corresponding FTIR bands have been assigned from the potential energy distributions (PED) in terms of internal coordinates of the molecule estimated from the output of the DFT calculations. The pH-dependent normal Raman spectra of the molecule in aqueous solution have been recorded to elucidate the protonation effect and preferential existence of the tautomeric form/forms of the molecule in acidic, neutral, and alkaline media. The SERS spectra of the molecule adsorbed on the nanocolloidal silver surface at various pH values are also reported. The appearance of overlapped Ag-N and Ag-S stretching vibrations, considerable red shift of the 1488 cm-1 band, and enhancement of all the bands principally representing the in-plane vibrations of the A′ species of the thione form of the molecule in the SERS spectra suggest that the molecules are adsorbed onto the nanocolloidal silver surface through the lone pair electrons of N 1 and S 6 atoms with the molecular plane tilted with respect to the silver surface at acidic, neutral, and alkaline pH.
Charge transfer complexes of some thiazoles and benzothiazoles with certain nitrobenzene derivatives
Spectrochimica Acta Part A: Molecular Spectroscopy, 1990
Interaction of some thiazole and benzothiazole derivatives as donors with certain di-and trinitrobenzene derivatives as acceptors results in the formation of 1:l molecular species. The infrared, NMR and ultraviolet analysis of the complexes with non-acidic acceptors reveals the presence of R--A* interaction from a HOMO of the thiazole nucleus or the phenyl moiety of the benzothiazoles to a LUMO of the benzene ring of the acceptors. The existence of this type of interaction is supported by HMO calculations on the donor molecules. On the other hand, the molecular complexes derived from acidic acceptors are stabilized, in addition to the n-JC* interaction, by proton transfer from the hydroxyl or carboxylic group of the acceptor to the amino group of the aminothiazole donors. The ionization potentials of donors, electron affinities of acceptors as well as the energy of the CT complexes were computed from their U.V. and visible spectra.
The Journal of Physical Chemistry B, 2006
In this work piperazine-1-carbodithioic acid (PZCDT) and piperazine-1,4-dicarbodithioic acid (PZbCDT) were synthesized. These analytes PZCDT and PZbCDT have chair conformations, which is expected to give specific surface-enhanced Raman scattering (SERS) effects on individual bands. SERS, UV-Visible, TEM and DFT methods have proved that the dithiocarbamate moiety is a potential and suitable functional group for silver and ZnO nanoparticles (AgNPs and ZnONPs). The enhancement mechanism and enhancement factors in both SERS@AgNPs and SERS@ZnONPs are also discussed. Two new strong bands appear at 1630, 1286 cm À1 with very large intensity in SERS@AgNPs, which signifies the conversion of the C-N bond of the dithiocarbamate moiety into C]N bonds. The SERS signatures that are observed are quite different in SERS@AgNPs and SERS@ZnONPs. PAPER adenine, benzenethiol derivatives etc. The -N site of the PZ ring (aer removal of H atom) is associated to the -dithiocarbamate moiety.