THEORETICAL TREATMENT OF THE SPECTROSCOPICAL DATA OF A STRONG HYDROGEN-BOND WITH A BROAD SINGLE-MINIMUM PROTON POTENTIAL

On the basis of ab initio MP2 calculations with the 3-21G* basis set, we simulated the interaction of the hydrogen bond complex methanesulfonic acid-dimethyl sulfoxide base with electrical fields simulating the environment. We compared the theoretical results with experimental ones. The potential energy surface is a broad flat single minimum also if strong electrical fields are present. The OH and OO modes are almost uncoupled. The lowest energy levels and thus the force constant of the hydrogen bond vibrations are almost independent of the external electrical field. We also performed vibrational analysis for 13 investigated strong largely symmetrical hydrogen bonds with the semiempirical MNDO/H procedure. The calculation of the hydrogen bond vibration shows for all complexes very good agreement with the experimental results. It is shown that the hydrogen bond vibration is very complicated and does not include the whole mass of the complex.