Ab initio prediction of the vibrational spectrum of the hydrogen-bonded complex H2CO...HOCN

The vibrational features characterising the hydrogen-bonded interaction between H2CO and HOC=N have been studied. The vibrational frequencies, IR intensities and Raman activities for free and complexed H2CO and HOC=N have been predicted by ab initio calculations with the 6-31G basis set. It was established that the complexation leads to changes in the vibrational characteristics for the stretching and deformation vibrations. The most sensitive vibrations to the complexation are the stretching O-H and C=O vibrations, involved in the hydrogen bonding. Their frequencies are shifted to lower wavenumbers. The changes in the vibrational characteristics for stretching O-H vibration are larger than the corresponding changes for the stretching C=O vibration. The remaining vibrations (stretching and deformation) are less sensitive to the hydrogen bonding. Their vibrational characteristics are changed with smaller magnitude. (C) 1998 Elsevier Science B.V. All rights reserved.