Boussessi Rahma, Senent María Luisa
Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, IEM-CSIC, Unidad Asociada GIFMAN, CSIC-UHU, Serrano 121, Madrid 28006, Spain.
Phys Chem Chem Phys. 2020 Oct 28;22(41):23785-23794. doi: 10.1039/d0cp03315d.
The far infrared spectra of three deuterated isotopologues of ethylene glycol, CH2OD-CH2OD, CH2OD-CH2OH and CH2OH-CH2OD, where the latter two species differ in their intramolecular hydrogen-bonding arrangement, are studied using highly correlated ab initio methods, vibrational second order perturbation theory and a variational procedure of reduced dimensionality. New subroutines suitable for the study of large systems with more than two interacting large amplitude motions were implemented and applied. The molecular symmetry of ethylene glycol decays by the formation of weak intramolecular bonds producing very asymmetrical stable structures. Three internal rotations contribute to the formation of a very anisotropic potential energy surface and to the puzzling distribution of the rovibrational energy levels. The ground vibrational state rotational constants and the centrifugal distortion constants (S-reduction, Ir representation) corresponding to the aGg' (G1) and gGg' (G2) forms are provided for the studied isotopologues. The low-lying vibrational levels up to 550 cm-1 are obtained variationally for J = 0. Two series of sublevels of the ground vibrational state are obtained: eight components localized in G1 lying between 0.0 and 0.3 cm-1 and eight sublevels localized in G2 lying between 138.1 and 138.4 cm-1. The gap between both sets is lower in CH2OD-CH2OD and more dispersed in the monodeuterated variety.
使用高度相关的从头算方法、振动二阶微扰理论和降维变分程序，研究了乙二醇的三种氘代同位素异构体CH2OD-CH2OD、CH2OD-CH2OH和CH2OH-CH2OD的远红外光谱，其中后两种异构体在分子内氢键排列上有所不同。实现并应用了适用于研究具有两个以上相互作用的大振幅运动的大系统的新子程序。乙二醇的分子对称性通过形成弱分子内键而衰减，从而产生非常不对称的稳定结构。三个内旋转有助于形成非常各向异性的势能面，并导致振转能级的分布令人费解。给出了所研究的同位素异构体对应于aGg'（G1）和gGg'（G2）形式的基振动态转动常数和离心畸变常数（S约化，Ir表示）。对于J = 0，变分得到了高达550 cm-1的低振动态能级。得到了基振动态的两个系列子能级：八个位于G1中的分量，位于0.0至0.3 cm-1之间，八个位于G2中的子能级，位于138.1至138.4 cm-1之间。两组之间的间隙在CH2OD-CH2OD中较低，在单氘代变体中更分散。
