An experimental study of the structural and vibrational properties of sesquiterpene lactone cnicin using FT-IR, FT-Raman, UV-visible and NMR spectroscopies

Fernando Chain, Elida Romano, PATRICIO ALEJANDRO LEYTON BONGIORNO, Carolina Paipa, César Atilio Nazareno Catalán, Mario Antonio Fortuna, Silvia Antonia Brandán

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27 Scopus citations

Abstract

An experimental and theoretical investigation of cnicin is presented, combining the use of infrared, Raman, NMR and UV-visible spectroscopies with density functional theory (DFT) that employs hybrid B3LYP exchange correlation functional and a 6-31G* basis set. The molecular electrostatic potentials, atomic charges, bond orders, stabilization energies, topological properties and energy gap are presented by performing NBO, AIM and HOMO-LUMO calculations at the same level of theory as cnicin. A complete vibrational compound assignment was performed by employing internal coordinate analysis and a scaled quantum mechanical force field (SQMFF) methodology. Comparisons between the theoretical and experimental vibrational and ultraviolet-visible spectra show a strong concordance. The geometrical parameters and NBO studies suggest a probable negative Cotton effect for cnicin, which can be attributed to the π → π* transition for an α,β-unsaturated γ-lactone, as reported in the literature.

Original languageEnglish
Pages (from-to)160-169
Number of pages10
JournalJournal of Molecular Structure
Volume1065-1066
Issue number1
DOIs
StatePublished - 22 May 2014

Keywords

  • Cnicin
  • DFT calculations
  • Force field
  • Molecular structure
  • Vibrational spectra

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