• portisins;
  • kinetics;
  • transition state theory;
  • DFT;
  • isobaric thermal capacity;
  • entropy


The kinetics of an important rotamerization occurring in vinylpyranoanthocyanin-phenol pigment (Portisin) was analyzed according to the transition state (TS) formalism. The relevant stationary states, the TS and the equivalent minima, were fully characterized. This included the optimization of the respective geometries and the analytical calculation of all vibrational frequencies. The reaction coordinate was identified, as associated with a single imaginary frequency in TS, and an appropriate intrinsic coordinate analysis (IRC) ensured that this state was connected with the correspondent equivalent minima. For the minimum, the harmonic and one-dimensional hindered rotor models were used to describe the reaction coordinate. The activation thermodynamics properties were then evaluated. The results obtained were interpreted according to the theoretical models assumed. The results are important for a prompt result for this group of portisins. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010