Features of strong O-H•••O and N-H•••O hydrogen bond manifestation in vibrational spectra

The work deals with the establishment of the dependence of the vibrational frequencies of strong O-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonds for the diagnosing the bonds themselves. To this end, the Raman spectra of a large number of different normal and deutero-substituted crystals characterized by the presence of strong O-H center dot center dot center dot O and N-H center dot center dot center dot O bonds are measured and the quantum chemical calculation is performed for one of these compounds. The dependence of the O-H stretching frequency on the O center dot center dot center dot O distance is constructed differing from that previously known for short O center dot center dot center dot O contacts. The mechanisms of significant broadening of the O-H vibration band in strong O-H center dot center dot center dot O hydrogen bonds are considered. Different dependences of the N-H vibrational frequencies in N-H center dot center dot center dot O bonds are reported and the causes of this diversity are discussed.