Solution and Solid-State Effects on NMR Chemical Shifts in Sesquiterpene Lactones: NMR, X-ray, and Theoretical Methods

0375520 - ÚOCHB 2012 RIV US eng J - Článek v odborném periodiku
Dračínský, Martin - Buděšínský, Miloš - Warzajtis, B. - Rychlewska, U.
Solution and Solid-State Effects on NMR Chemical Shifts in Sesquiterpene Lactones: NMR, X-ray, and Theoretical Methods.
Journal of Physical Chemistry A. Roč. 116, č. 1 (2012), s. 680-688. ISSN 1089-5639. E-ISSN 1520-5215
Grant CEP: GA AV ČR KJB400550903; GA ČR GA203/09/1919
Výzkumný záměr: CEZ:AV0Z40550506
Klíčová slova: crystal-structures spectroscopy * crystallography * quantum * pseudopotentials
Kód oboru RIV: CF - Fyzikální chemie a teoretická chemie
Impakt faktor: 2.771, rok: 2012

Selected guaianolide type sesquiterpene lactones were studied combining solution and solid-state NMR spectroscopy with theoretical calculations of the chemical shifts in both environments and with the X-ray data. The experimental H-1 and C-13 chemical shifts in solution were successfully reproduced by theoretical calculations (with the GIAO method and DFT B3LYP 6-31++G**) after geometry optimization (DFT B3LYP 6-31 G**) in vacuum. The GIPAW method was used for calculations of solid-state C-13 chemical shifts. The studied cases involved two polymorphs of helenalin, two pseudopolymorphs of 6 alpha-hydroxydihydro-aromaticin and two cases of multiple asymmetric units in crystals: one in which the symmetry independent molecules were connected by a series of hydrogen bonds (geigerinin) and the other in which the symmetry independent molecules, deprived of any specific intermolecular interactions, differed in the conformation of the side chain (badkhysin). Geometrically different molecules present in the crystal lattices could, be easily distinguished in the solid-state NMR spectra. Moreover, the experimental differences in the C-13 chemical shifts corresponding to nuclei in different polymorphs or in geometrically different molecules were nicely reproduced with the GIPAW calculations.
Trvalý link: http://hdl.handle.net/11104/0006929