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 pi -> pi* transition for an alpha,beta-unsaturated gamma-lactone, as reported in the literature. (C) 2014 Elsevier B.V. All rights reserved.