Barriers to internal rotation and tunnelling splittings of the torsional states in the HO(CH₂)OH, DO(CH₂)OH and DO(CH₂)OD molecules

Torsional States and Tunneling Probability in HOSOH, DOSOD, and DOSOH Molecules Analyzed at the CBS Limit

“…The 2D surfaces of the kinematic coefficients calculated at the MP2/cc-pVQZ level of theory are presented in Figure 1 of the Supporting Information. Comparing the shape of the 2D PES and 2D surfaces of the components of the dipole moment of the methanediol (MD) 23,25 and hydrogen trioxide (HT) 24,26 molecules to the HOSOH molecule presented in Figures 3 and 4 helps to conclude that they are very similar. 2D surfaces of the kinematic coefficients F γ 1 γ 1 and F γ 2 γ 2 equivalent up to 90°r otation through an angle about an axis normal to the coordinate plane and passing through a point with coordinates (180, 180°).…”

“…This means that in the first case, the total wave function must be antisymmetric to the symmetry operation (15)(24) (symmetry species B), while for the DOSOD molecule it must be symmetric to the corresponding operation (symmetry species A). The torsional wave functions of type A (symmetric vibrations) as well as ortho-states spin wave functions are symmetric to operation (15) (24), and the torsional wave functions of type B (antisymmetric vibrations) as well as parastates spin wave functions are antisymmetric to operation (15) (24). Because the HOSOH and DOSOD are the near prolate asymmetric top molecules, the rotational wave functions J k a k c (J, k a , k c rotational quantum numbers) with k a + k c = even are symmetric to operation (15) (24), and the rotational wave functions with k a + k c = odd are antisymmetric to operation (15) (24).…”

“…The torsional wave functions of type A (symmetric vibrations) as well as ortho-states spin wave functions are symmetric to operation (15) (24), and the torsional wave functions of type B (antisymmetric vibrations) as well as parastates spin wave functions are antisymmetric to operation (15) (24). Because the HOSOH and DOSOD are the near prolate asymmetric top molecules, the rotational wave functions J k a k c (J, k a , k c rotational quantum numbers) with k a + k c = even are symmetric to operation (15) (24), and the rotational wave functions with k a + k c = odd are antisymmetric to operation (15) (24). The possible combinations of three wave functions for the trans-conformer of the HOSOH and DOSOD molecules are presented in Table 7.…”

“…Recently, we performed calculations of the torsional states of HO­(CH 2 )­OH and HOOOH molecules as well as their deuterated derivatives. , The torsional states were classified using the molecular symmetry group C 2V ( M ), and it was found that the calculated tunneling frequencies in these molecules differ significantly (by several orders of magnitude), but both of them can be assigned to nonrigid molecules. We confirmed that the stability of the cis-conformer in the first molecule is quite uncertain and can only be realized at very low temperatures.…”

“…Besides, it was shown that in the case of low values of tunneling frequencies, the correct procedure for calculating 2D PES and kinematic coefficients, as well as taking into account the molecular symmetry, is particularly important . In this study, using previously developed methods, − we calculated 2D potential energy surfaces and kinematic coefficients with a complete account of the properties of the molecular symmetry group C 2V ( M ), which describes the symmetry properties of both conformers of HOSOH and DOSOD molecules. Then, the values of the energy of the stationary torsional states of three analyzed molecules were calculated and their torsional IR spectra were modeled at various temperatures.…”