Division of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, Zagreb, Croatia.
J Phys Chem A. 2012 Aug 16;116(32):8397-406. doi: 10.1021/jp306070x. Epub 2012 Aug 2.
The electronic charge redistribution and the infrared intensities of the two types of intramolecular hydrogen bonds, O-H···O and O-H···π, of o-hydroxy- and o-ethynylphenol, respectively, together with a set of related intermolecular hydrogen bond complexes are described in terms of atomic charges and charge fluxes derived from atomic polar tensors calculated at the B3LYP/cc-pVTZ level of theory. The polarizable continuum model shows that both the atomic charges and charge fluxes are strongly dependent on solvent. It is shown that their values for the OH bond in an intramolecular hydrogen bond are not much different from those for the "free" OH bond, but the changes are toward the values found for an intermolecular hydrogen bond. The intermolecular hydrogen bond is characterized not only by the decreased atomic charge but also by the enlarged charge flux term of the same sign producing thus an enormous increase in IR intensity. The overall behavior of the charges and fluxes of the hydrogen atom in OH and ≡CH bonds agree well with the observed spectroscopic characteristics of inter- and intramolecular hydrogen bonding. The main reason for the differences between the two types of the hydrogen bond lies in the molecular structure because favorable linear proton donor-acceptor arrangement is not possible to achieve within a small molecule. The calculated intensities (in vacuo and in polarizable continuum) are only in qualitative agreement with the measured data.
本文分别用原子电荷和从原子极性张量计算得到的电荷通量，描述了邻羟基苯酚和邻乙炔基苯酚中两种类型的分子内氢键（O-H···O 和 O-H···π）的电子电荷重分布和红外强度，以及一系列相关的分子间氢键复合物。极化连续体模型表明，原子电荷和电荷通量都强烈依赖于溶剂。结果表明，它们在分子内氢键中 OH 键的原子电荷值与“自由”OH 键的原子电荷值没有太大区别，但变化趋势是朝着分子间氢键的原子电荷值发展。分子间氢键的特点不仅是原子电荷减小，而且相同符号的电荷通量项增大，从而导致红外强度的巨大增加。OH 和 ≡CH 键中氢原子的电荷和通量的整体行为与观察到的分子间和分子内氢键的光谱特征非常吻合。两种氢键之间的差异主要归因于分子结构，因为在小分子中不可能实现有利的质子供体-受体线性排列。计算得到的强度（真空中和极化连续体中）仅与测量数据定性一致。
