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Résumé
Helicenes constitute a special class of molecules combining helical conformation with π-electron delocal- ization. These confer to helicenes specific chirooptical properties. In this article, we investigate the vibrational signatures thanks to the simulation of vibrational Raman optical activity (VROA) spectra. For that, four representative helicenes: hexahelicene, tetrathia-[7]-helicene, and its pyrrole and furan analogs have been simulated and interpreted using a recently implemented analytical scheme. Helicenes show intense VROA peaks attributed to their π-conjugated structure and associated with collective vibrational modes. In hexahelicene, the dominant VROA features are due to vibrational modes involving motions of the carbon skeleton and H-wagging, but the intensity finds its source almost exclusively in the former. In the case of the three heterohelicenes, the previous statement is also verified, and on changing the heteroatoms, similar modes presenting comparable atomic contribution patterns have been highlighted, though the vibrational and electronic properties are modified. Some fingerprints could therefore be associated with the helicity of the system. In particular, in forward spectra, most of the VROA bands are positive for left-handed helicenes. Nevertheless, the spectral patterns are quite complex, and no easy rule-of-thumb could distinguish between the different heterohelicenes. Then, considering the fact that most of the contributions originate from the C atoms (group coupling matrices decomposition), it can be concluded that the major role of the heteroatom is restricted to modifying the geometry and the normal modes. At last, the small impact of the gauge-origin on the calculated spectra using a relatively modest basis set (rDPS:3-21G) is demonstrated here in the case of the tetrathia-[7]-helicene molecule presenting a C symmetry. This further demonstrates the adequacy of this basis set for VROA calculations.
langue originale | Anglais |
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Pages (de - à) | 1261-1278 |
Nombre de pages | 18 |
journal | Journal of Computational Chemistry |
Volume | 30 |
Numéro de publication | 8 |
Les DOIs | |
Etat de la publication | Publié - 1 juin 2009 |
Empreinte digitale
Examiner les sujets de recherche de « Vibrational raman optical activity of π-conjugated helical systems: Hexahelicene and heterohelicenes ». Ensemble, ils forment une empreinte digitale unique.Projets
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Développement du Centre ISCF
Champagne, B., VIGNERON, J., Derycke, I., FRIPIAT, J., Lambin, P., Schievekamp, I., Vercauteren, D., Wautelet, F. & Wouters, J.
1/01/95 → 31/12/12
Projet: Recherche
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Plateforme Technologique Calcul Intensif
Benoît Champagne (!!Manager)
Plateforme technologique Calcul intensifEquipement/installations: Plateforme technolgique
Thèses de l'étudiant
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Elaboration of quantum chemistry methods for predicting and interpreting vibrational Raman optical activity: applications to helical structures
Auteur: Liégeois, V., 19 juin 2008Superviseur: Thiry, P. (Jury), Verbiest, T. (Personne externe) (Jury), Hug, W. (Personne externe) (Jury), Ruud, K. (Personne externe) (Jury), Su, B. L. (Jury) & Champagne, B. (Promoteur)
Student thesis: Doc types › Docteur en Sciences