Potential and kinetic interaction of two internal tops in molecules belonging to C2v(M) molecular symmetry group

Fourier analysis of the kinetic and potential interactions of non-coaxial internal tops in the molecules C₆H₄(OH)₂, HO(CH₂)OH, HOOOH, HOSOH, HSSSH, and HSOSH was carried out. It was found that for the all six molecules, in which both tops are characterized by a period 2 $\pi$, the harmonics with a period of $\pi$ are dominate, with its contribution to the Fourier representation of potential surfaces increasing in the sequence mentioned above. Contributions of internal tops interactions to the kinetic and potential energies were determined for analyzed molecules. The influence of potential and kinetic interactions of internal tops on 1) the features of tunneling splitting of the ground and excited torsional states of molecules, 2) the landscape of 2D potential energy surfaces, 3) frequencies of fundamental torsional vibrations of hydroxyl and thiol groups, 4) the ratio of trans - and cis - conformer energies is also analyzed.