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丙二醛中C-H/O-H伸缩振动的理论研究

Theoretical study of the C-H/O-H stretching vibrations in malonaldehyde.

作者信息

Pitsevich G A, Malevich A E, Kozlovskaya E N, Doroshenko I Yu, Pogorelov V E, Sablinskas V, Balevicius V

机构信息

Belarusian State University, Minsk, Belarus.

Belarusian State University, Minsk, Belarus.

出版信息

Spectrochim Acta A Mol Biomol Spectrosc. 2015 Jun 15;145:384-393. doi: 10.1016/j.saa.2015.02.067. Epub 2015 Feb 26.

Abstract

IR and Raman spectra of the malonaldehyde molecule and its deuterated analogues were calculated in the B3LYP/cc-pVQZ approximation. Anharmonicity effects were taken into account both in the context of a standard model of the second order perturbation theory and by constructing the potential energy surfaces (PES) with a limited number of dimensions using the Cartesian coordinates of the hydroxyl hydrogen atom and the stretching coordinates of С-Н, C-D, O-H, and O-D bonds. It was shown that in each of the two equivalent forms of the molecule, besides the global minimum, an additional local minimum at the PES is formed with the energy more than 3,000 cm(-1) higher than the energy in the global minimum. Calculations carried out by constructing the 2D and 3D PESs indicate a high anharmonicity level and multiple manifestations of the stretching О-Н vibrations, despite the fact that the model used does not take into account the splitting of the ground-state and excited vibrational energy levels. In particular, the vibration with the frequency 3,258 cm(-1) may be associated with proton transfer to the region of a local minimum of energy. Comparing the results obtained with the experimental data presented in the literature allowed us to propose a new variant of bands assignments in IR and Raman spectra of the molecule in the spectral region 2,500-3,500 cm(-1).

摘要

在B3LYP/cc-pVQZ近似下计算了丙二醛分子及其氘代类似物的红外光谱和拉曼光谱。在二阶微扰理论的标准模型框架内以及通过使用羟基氢原子的笛卡尔坐标和C-H、C-D、O-H和O-D键的伸缩坐标构建有限维数的势能面(PES),考虑了非谐性效应。结果表明,在分子的两种等效形式中,除了全局最小值外,在PES上还形成了一个额外的局部最小值,其能量比全局最小值中的能量高3000 cm⁻¹以上。通过构建二维和三维PES进行的计算表明,尽管所使用的模型没有考虑基态和激发振动态能级的分裂,但非谐性水平很高,且伸缩O-H振动有多种表现形式。特别是,频率为3258 cm⁻¹的振动可能与质子转移到局部能量最小值区域有关。将所得结果与文献中给出的实验数据进行比较,使我们能够提出该分子在2500 - 3500 cm⁻¹光谱区域的红外光谱和拉曼光谱谱带归属的新变体。

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