Institute of Chemistry, University of Silesia, Katowice, Poland.
J Phys Chem A. 2011 May 5;115(17):4202-13. doi: 10.1021/jp107114h. Epub 2011 Apr 6.
This article presents the investigation results of the polarized IR spectra of the hydrogen bond in N-phenylacrylamide crystals measured in the frequency range of the proton and deuteron, ν(N-H) and ν(N-D), stretching vibration bands. The basic spectral properties of the crystals were interpreted quantitatively in terms of the "strong-coupling" theory. The proposed model of the centrosymmetric dimer of hydrogen bonds facilitated the explanation of the well-developed, two-branch structure of the ν(N-H) and ν(N-D) bands as well as the isotopic dilution effects in the spectra. The vibronic mechanism of the generation of the long-wave branch of the ν(N-H) band ascribed to the excitation of the totally symmetric proton vibration was elucidated. The complex fine structure pattern of ν(N-H) and ν(N-D) bands in N-phenylacrylamide spectra in comparison with the spectra of other secondary amide crystals (e.g., N-methylacetamide and acetanilide) can be accounted for in terms of the vibronic model for the forbidden transition breaking in the dimers. On the basis of the linear dichroic and temperature effects in the polarized IR spectra of N-phenylacrylamide crystals, the H/D isotopic "self-organization" effects were revealed.
本文介绍了在质子和氘核伸缩振动带 ν(N-H) 和 ν(N-D) 的频率范围内测量的 N-苯丙烯酰胺晶体氢键的偏振红外光谱的研究结果。根据“强耦合”理论，对晶体的基本光谱性质进行了定量解释。所提出的氢键中心对称二聚体模型有助于解释 ν(N-H) 和 ν(N-D) 带的发达的、两分支结构以及谱中的同位素稀释效应。阐明了归因于完全对称质子振动激发的 ν(N-H) 长波支的振子机制。与其他仲酰胺晶体（例如 N-甲基乙酰胺和乙酰苯胺）的光谱相比，N-苯丙烯酰胺光谱中 ν(N-H) 和 ν(N-D) 带的复杂精细结构模式可以根据二聚体中禁阻跃迁的振子模型来解释。基于 N-苯丙烯酰胺晶体偏振红外光谱的线二色性和温度效应，揭示了 H/D 同位素“自组织”效应。
