Quantum-mechanical calculations of the structure and dynamics of conformationally nonrigid carbonyl compound molecules in the ground and excited electronic states

The results of quantum-mechanical studies of several conformationally nonrigid carbonyl compound molecules in the ground and lower electronically excited states are considered. At the first stage, various ab initio methods were used to calculate potential energy surfaces. Based on these results, the quantum-mechanical problem of torsional and inversion motions of nuclei was solved at the second stage for both one- and two-dimensional models. These large-amplitude vibrations were found to be coupled together. The calculation results obtained at both stages were compared with the corresponding experimental data to estimate the reliability of these methods in describing fine conformational characteristics of molecules.