Barriers for cation reorientation in pyridinium iodide studied by an atom–atom and DFT methods

The heights of barriers for reorientation of the pyridinium cation in a molecular–ionic system of pyridinium iodide have been calculated by the traditional atom–atom approach taking into regard the London dispersion and repulsive interactions and the calculations methods of quantum chemistry DFT (B3LYP/3-21G*) and PM3. The parallel application of the two approaches permitted a very good reproduction of the height of the cation reorientation barriers. q 2004 Elsevier B.V. All rights reserved.