A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH] + linear complex along the proton transfer reaction profile is given, and the laws governing the diagnostic parameters — potential descriptors of the dynamics of this process — are established. The surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the proton transfer reaction path in the system studied are calculated. It has been shown that when the [HCNH] + and NCH fragments come closer together, a noticeable distortion of the forms of their skeletal vibrations occurs, up to complete mixing into the symmetric and antisymmetric forms. The frequency of the longitudinal vibration of the central proton ν (NH) varies along the reaction path from ~ 3600 to ~ 500 cm-1. In the region of intersection of the terms ν (NH) and ν (CN) an abrupt nature of frequency change is detected.

The IR spectra of sevoflurane + acetone mixtures in liquefied Xe were studied at T ~ 165 – 190 K. Complex formation stabilized by noncovalent interactions of weak H-bond type has been identified on the basis of changes found at selected bands of both components. Quantum-chemical calculations made on MP2/6-311++G(d,p) level, show that the spectrum in the region of stretching vibrations of CH and CH2 groups is formed due to anharmonic effects, specifically Fermi resonances.