Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (02): 303-308.doi: 10.3866/PKU.WHXB201112013


Effects of Mode-Mode Coupling on Vibrational Frequency Blue Shift in Improper H-Bonded Systems

KONG Xiang-Lei   

  1. State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. China
  • Received:2011-08-31 Revised:2011-11-24 Published:2012-01-11
  • Contact: KONG Xiang-Lei
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21052001).

Abstract: Bond shortening of NH/CH due to improper hydrogen bonding is always thought to be accompanied by a blue shift in its corresponding frequency. However, results here show that owing to anharmonic effects, especially the contribution of mode-mode coupling, the blue shift could be greatly decreased. The strong interaction may even, in some cases, cause the previously predicted blue-shifting frequencies by harmonic methods to be red-shifted instead in the gas phase. Though these results need to be clearly verified by further infrared (IR) spectrum experiments in the gas phase for the selected systems, comparisons with previous IR results obtained from matrix isolation experiments strongly support the results of the calculations.

Key words: Improper hydrogen bond, Mode-mode coupling, Blue shift, Infrared spectrometry, Anharmonic effect