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  Guanidine and guanidinium cation in the excited state—theoretical investigation

Antol, I., Glasovac, Z., Crespo-Otero, R., & Barbatti, M. (2014). Guanidine and guanidinium cation in the excited state—theoretical investigation. The Journal of Chemical Physics, 141(7), 074307/1-074307/10. doi:10.1063/1.4892569.

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 Urheber:
Antol, Ivana1, Autor
Glasovac, Zoran1, Autor
Crespo-Otero, Rachel2, Autor           
Barbatti, Mario2, Autor           
Affiliations:
1Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, P.O. Box 180, HR-10002 Zagreb, Croatia , ou_persistent22              
2Research Group Barbatti, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445594              

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 Zusammenfassung: Diverse ab initio and density-functional-theory methods were used to investigate geometries, energies, and electronic absorption spectra of guanidine and its protonated form, as well as their photo-deactivation processes. It was shown that the guanidine is a weakly absorbing species with the excitation spectrum consisting mostly of transitions to the Rydberg excited states and one valence n-π4 state. The lowest energy band has a maximum at ca. 6.9 eV (∼180 nm). The protonation of guanidine affects its excitation spectrum substantially. A major shift of the Rydberg states to higher energies is clearly visible and strongly absorbing transitions from the ground state to the π34 and π24 states appears at 7.8 eV (∼160 nm). Three low-lying conical intersections (two for guanidine and one for protonated guanidine) between the ground state and the first excited singlet state were located. They are accessible from the Franck–Condon region through amino N–H stretching and out-of-plane deformations in guanidine and protonated guanidine, respectively. The relaxation of the π3-3s Rydberg state via amino N–H bond stretching was hindered by a barrier. The nondissociated conical intersection in protonated guanidine mediates the radiationless deactivation of the compound after excitation into the π34 state. This fact is detrimental for the photostability of guanidine, since its conjugate acid is stable in aqueous solution over a wide pH range and in protein environment, where guanidinium moiety in arginine is expected to be in a protonated form.

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Sprache(n): eng - English
 Datum: 2014-05-132014-07-282014-08-182014
 Publikationsstatus: Erschienen
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 Ort, Verlag, Ausgabe: -
 Inhaltsverzeichnis: -
 Art der Begutachtung: Expertenbegutachtung
 Identifikatoren: DOI: 10.1063/1.4892569
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Titel: The Journal of Chemical Physics
  Andere : J. Chem. Phys.
Genre der Quelle: Zeitschrift
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Ort, Verlag, Ausgabe: Woodbury, N.Y. : American Institute of Physics
Seiten: - Band / Heft: 141 (7) Artikelnummer: - Start- / Endseite: 074307/1 - 074307/10 Identifikator: ISSN: 0021-9606
CoNE: https://pure.mpg.de/cone/journals/resource/954922836226