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dc.contributor.author
Borba, Ana
dc.contributor.author
Gomez Zavaglia, Andrea
dc.contributor.author
Fausto, Rui
dc.date.available
2016-12-26T20:14:12Z
dc.date.issued
2014-10
dc.identifier.citation
Borba, Ana; Gomez Zavaglia, Andrea; Fausto, Rui; Conformers, infrared spectrum, UV-induced photochemistry, and near-IR-induced generation of two rare conformers of matrix-isolated phenylglycine; American Institute of Physics; Journal of Chemical Physics; 141; 15; 10-2014; 154306-154314
dc.identifier.issn
0021-9606
dc.identifier.uri
http://hdl.handle.net/11336/10223
dc.description.abstract
The conformational space of α-phenylglycine (PG) have been investigated theoretically at both the DFT/B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) levels of approximation. Seventeen different minima were found on the investigated potential energy surfaces, which are characterized by different dominant intramolecular interactions: type I conformers are stabilized by hydrogen bonds of the type N-H⋯O=C, type II by a strong O-H⋯N hydrogen bond, type III by weak N-H⋯O-H hydrogen bonds, and type IV by a C=O⋯H-C contact. The calculations indicate also that entropic effects are relevant in determining the equilibrium populations of the conformers of PG in the gas phase, in particular in the case of conformers of type II, where the strong intramolecular O-H⋯N hydrogen bond considerably diminishes entropy by reducing the conformational mobility of the molecule. In consonance with the relative energies of the conformers and barriers for conformational interconversion, only 3 conformers of PG were observed for the compound isolated in cryogenic Ar, Xe, and N2 matrices: the conformational ground state (ICa), and forms ICc and IITa. All other significantly populated conformers existing in the gas phase prior to deposition convert either to conformer ICa or to conformer ICc during matrix deposition. The experimental observation of ICc had never been achieved hitherto. Narrowband near-IR irradiation of the first overtone of νOH vibrational mode of ICa and ICc in nitrogen matrices (at 6910 and 6930 cm-1, respectively) led to selective generation of two additional conformers of high-energy, ITc and ITa, respectively, which were also observed experimentally for the first time. In addition, these experiments also provided the key information for the detailed vibrational characterization of the 3 conformers initially present in the matrices. On the other hand, UV irradiation (λ = 255 nm) of PG isolated in a xenon matrix revealed that PG undergoes facile photofragmentation through two photochemical pathways that are favored for different initial conformations of the reactant: (a) decarboxylation, leading to CO2 plus benzylamine (the dominant photofragmentation channel in PG cis-COOH conformers ICa and ICc) and (b) decarbonylation, with generation of CO plus benzonitrile, H2O and H2 (prevalent in the case of the trans-COOH conformer, IITa).
dc.format
application/pdf
dc.language.iso
eng
dc.publisher
American Institute of Physics
dc.rights
info:eu-repo/semantics/openAccess
dc.rights.uri
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.subject
Matrix Isolation
dc.subject
Nir
dc.subject
Phenyl Glycine
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Otras Ingenierías y Tecnologías
dc.subject.classification
Otras Ingenierías y Tecnologías
dc.subject.classification
INGENIERÍAS Y TECNOLOGÍAS
dc.title
Conformers, infrared spectrum, UV-induced photochemistry, and near-IR-induced generation of two rare conformers of matrix-isolated phenylglycine
dc.type
info:eu-repo/semantics/article
dc.type
info:ar-repo/semantics/artículo
dc.type
info:eu-repo/semantics/publishedVersion
dc.date.updated
2016-12-12T14:11:15Z
dc.journal.volume
141
dc.journal.number
15
dc.journal.pagination
154306-154314
dc.journal.pais
Estados Unidos
dc.journal.ciudad
New York
dc.description.fil
Fil: Borba, Ana. Universidad de Coimbra; Portugal
dc.description.fil
Fil: Gomez Zavaglia, Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigaciones en Criotecnología de Alimentos (i); Argentina. Universidad de Coimbra; Portugal
dc.description.fil
Fil: Fausto, Rui. Universidad de Coimbra; Portugal
dc.journal.title
Journal of Chemical Physics
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/doi/http://dx.doi.org/10.1063/1.4897526
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/url/http://aip.scitation.org/doi/full/10.1063/1.4897526
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