Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (08): 1609-1617.doi: 10.3866/PKU.WHXB201306032

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

Raman Spectra of Amino Wagging Vibrational Modes in p-π-Conjugated Molecules

TAO Sha, YU Li-Juan, WU De-Yin, TIAN Zhong-Qun   

  1. State Key Laboratory for Physical Chemistry of Solid Surfaces, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian Province, P. R. China
  • Received:2013-04-16 Revised:2013-05-31 Published:2013-07-09
  • Contact: WU De-Yin E-mail:dywu@xmu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (91027009, 21021002, 20973143), National Key Basic Research Program of China (973) (2009CB930703), and Xiamen University, China (2010121020).

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Abstract:

Raman spectroscopy has been widely used as a non-destructive testing and molecular recognition technology, providing fingerprint information for chemical and biological molecular structures. One type of out-of-plane bending vibration observed in Raman spectroscopy is named the‘wagging vibration’. The Raman signal of the wagging mode is very sensitive; not only the vibrational frequency but also the Raman intensity depends strongly on environment factors. In this report, density functional theory (DFT) calculations are used to study the equilibrium structures, binding interactions, and Raman spectra of vinylamine and aniline as well as their complexes with silver clusters and water clusters. Vinylamine-silver and aniline-silver clusters were used to simulate the interactions of the molecules adsorbed on silver surfaces, while vinylamine-water and aniline-water clusters were used to investigate the hydrogen bonding interactions of vinylamine and aniline with water clusters. Our calculated results show that the Raman signal of the amino wagging mode strongly depends on the hydrogen bonding interaction of the nitrogen lone pair in the amino group with the O―H bond of water. Increasing the size of the water clusters causes a large blue shift and considerable enhancement in the intensity of the wagging vibration. When the polarized continuum model was used to consider the solvation effect, the electrostatic interaction contributing to the hydrogen bond was weakened. In this case, the simulated Raman spectra were similar to each other. For vinylamine and aniline interacting with silver clusters, the Raman signals of the amino wagging vibration were changed by the weak binding interaction, revealing the relationship between the abnormal signal of wagging vibrations and the weak interaction in p-π-conjugated systems.

Key words: Wagging vibration mode, Weak intermolecular interaction, Hydrogen bond, Vinylamine, Aniline, Raman spectroscopy, Density functional theory