Hydrogen bonding of isoindole-1,3-dione in reaction field: Vibrational spectroscopy study

The origin of the geometrical and spectroscopic changes in isoindole-1,3-dione molecule due to the hydrogen bonding (local electric field) is studied using ab initio and perturbation treatment of the Onsager model. In the case of CO, bond elongates and red-shifted CO stretch (s) mode results; in the case of N-H, bond contraction and blue-shifted NH s frequency is observed and for the C-H bond, both red-shifted and blue-shifted CH s mode are found. Furthermore, using vibrational Stark effect in the Onsager model we were able to determine the difference dipole moment and the difference polarizability of several stretching bands.