A computational investigation of the red and blue shifts in hydrogen bonded systems

Abstract

The present work reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic parameters are proposed, thereby generating new insight into both types of the frequency shifts. Thus, the frequency shifts in X—H—-Y hydrogen bonded systems at different H—Y distances are shown to correlate well with the Mulliken charges on H and Y, with the positive and negative charges on Y correlating with the blue and red shift of the frequency of X—H vibration, respectively. The role played by charge transfers at other parts of the interacting system is also discussed. Synopsis The blue and red shifts in vibrational frequency in X—H...Y hydrogen bonded systems as a function of H—-Y distance are shown to correlate well with the atomic charges on H and Y as well as other electrostatic parameters.