The IR spectra of solutions of mixtures of volatile anesthetics (enflurane, isoflurane) and dimethyl ether were studied by cryospectroscopy in the temperature range 120–160 K. The formation of complexes has been observed: dimers at lower concentrations and trimers at higher concentrations. The results of quantum-chemical calculations are in qualitative agreement with the results of measurements.

The IR spectra of CDF3 in the solid Ar and N2 matrices were measured and analyzed in the region of the Fermi polyads 2ν4/ν1/2ν2/ν4 + ν5, complicated by a close Fermi resonance ν4/ν3 + ν6. The symmetry lifting effect, observed in the N2 matrix, was found helpful for an accurate assignment of the individual components. The anharmonic calculation of the potential energy surface and the dipole moment function was performed on the MP2/aug-cc-pVTZ level. The unperturbed values of vibrational eigenstates were determined in the region of ν1 (CD stretching vibration) in both matrices. The experimental findings and theoretical analysis are in good agreement.

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 CH 2 groups is formed due to anharmonic effects, specifically Fermi resonances. Keywords: cryospectroscopy, sevoflurane, acetone, complex, noncovalent interactions, quantum-mechanical calculations.

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.

The sequences of Fermi resonances vs~2vb in the IR spectrum of a solution of fluoroform (CHF3) in liquefied krypton are investigated. Here vs is the CH stretching vibration, vb is the bending vibration. It is shown that for a correct description of resonance multiplets (polyads) at a high degree of vibrational excitation, it is necessary to use an extended set of spectroscopic parameters. In particular, it is necessary to take into account the dependence of the anharmonic interaction constant asbb on the vibrational quantum numbers. The conclusions are generalized for the arbitrary case of the CH-chromophore CHX3.

The reversible interaction of halothane (C2HBrClF3) with negatively charged local areas of molecular targets is defined in a large extent by the proton donor ability of CH group. This interaction leads to the formation of a hydrogen bond of the CH … B type. In the presence of heavy halogen atoms in the CHClBr group, the CX … B halogen bond can act as an alternative or additional target grip option. The results obtained by the cryospectroscopy method for solutions of halothane with large excess of trimethylamine in liquefied krypton suggest the trimer formation, stabilized by hydrogen and halogen bonds between this volatile anesthetic and electron donor targets.

The IR absorption spectra of solutions of mixtures of halothane (C 2 HBrClF 3 ) and trimethylamine ((CD 3 ) 3 N) in liquefied krypton were obtained and analyzed. Bands assigned to weak hydrogen-bonded complexes have been identified. In a series of temperature experiments on the change in the integral intensities of the bands of monomers and complexes, the enthalpy of formation of complexes was estimated. An extremely strong increase in the intensity of the second-order bands attributed to the first overtone of bending CH vibrations of halothane was found. The effect is determined by strong anharmonic interactions of a resonant nature (Fermi resonance and Darling–Dennison resonance). The results of ab initio calculations reproduce the experimentally observed effects.

— The sequences of Fermi resonances ν s ≈ 2ν b in the IR spectrum of a fluoroform solution (CHF 3 ) in liquefied krypton have been studied. Here, ν s is the CH-stretching vibration and ν b is the bending vibration. It has been shown that it is necessary to use an extended set of spectroscopic parameters for the correct description of resonant multiplets at a high degree of vibrational excitation. Among other factors, it is necessary to consider the dependence of the anharmonic interaction constant α sbb on the vibrational quantum numbers. The conclusions are generalized for the arbitrary case of the CH-chromophore CHX 3 .

The IR absorption spectra of solutions of mixtures of halothane (C2HBrClF3) and trimethylamine ((CD3) 3N) in liquefied krypton were obtained and analyzed. Bands assigned to weak hydrogen-bonded complexes have been identified. The enthalpy of formation was estimated in a series of temperature experiments on the change in the integral intensities of the bands of monomers and complexes An extremely strong increase in the intensity of the second-order bands attributed to the first overtone of the bending CH vibrations of halothane was found. The effect is determined by strong anharmonic interactions of a resonant nature (Fermi resonance and Darling-Dennison resonance). The results of ab initio calculations reproduce the effects observed in the experiment.

The IR spectra of mixtures of methoxyflurane and dimethyl ether are studied with the help of FTIR cryospectroscopy in liquefied Xe. The region of CH3 and CH stretching vibrations is examined taking into account the Fermi resonance effect. Comparative analysis of the experimental data and results of ab initio calculations show that the Cl2CH group of methoxyflurane is involved in complex formation which is stabilized by H-bond between H atom of this group and O atom of dimethyl ether predominantly.

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 profile of the proton transition reaction path is given, and the laws governing the diagnostic parameters, that is, potential descriptors of the dynamics of this process, are determined. We calculated the surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the reaction path of the proton transition in the system under study. When the fragments [HCNH]+ and NCH approach each other, 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. An abrupt frequency change is observed in the region of intersection of the terms ν(NH) and ν(CN).

The IR spectra of sevoflurane thorn dimethyl ether mixtures dissolved in liquid Kr are studied at T similar to 118 -155 K. The characteristic changes observed in numerous IR bands of both moieties suggest the formation of complexes stabilized by non covalent interactions of H-bond type. Estimations based on ab initio calculations including anharmonic effects are in line with the experimental findings. (C) 2020 Elsevier B.V. All rights reserved.

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 interplay of π-stacking and inter-stacking interactions in two-component organic crystals without conventional hydrogen bonds.

The IR spectra of isoflurane + dimethyl ether mixtures dissolved in liquid Kr are registered at T ~118-160 K. The results obtained at a wide range of relative concentrations suggest the formation of complexes stabilized by non-covalent interactions of H-bond type. Large excess of DME and low temperature favor trimer formation stabilized by interactions between two DME moieties and both CH groups of isoflurane predominantly. Estimations based on ab initio calculation of spectroscopic and thermodynamic parameters confirm the experimental findings.

The interactions between halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) and acetylene (C2H2) are studied by FTIR spectroscopy. Results obtained in liquid cryosolutions in Kr suggest weak complex formation stabilized by H - bond. The complexation enthalpy (similar to 11 kJ/mol) is evaluated in a series of temperature measurements (T similar to 120-160 K) of integrated intensity of selected bands performed in liquefied Kr. The quantum chemical MP2/6-311++G(2d,2p) calculations predict four different structures of the complex. The most stable and populated (94% at T similar to 120 K) structure corresponds to the H - bond between H atom of halothane and pi-electron of triple bond between C atoms of acetylene. Wave numbers of vibrational bands of the most stable structure are calculated in anharmonic approximation implemented in Gaussian program. (C) 2018 Elsevier B.V. All rights reserved.

The FTIR spectra of fluoroform + methyl fluoride mixtures trapped in argon and nitrogen matrices are studied at T-10-30 K. Spectroscopic changes observed in the region of the CH stretching mode of fluoroform are typical for weak blue shifting H - bonds of C-H center dot center dot center dot F type. The degeneracy lifting effect found on E- type bands of fluoroform interacted with methyl fluoride suggests the complex formation of a nonlinear form. The experimental results are confirmed by ab initio calculations of fluoroform + methyl fluoride based on the second order Moller-Plesset theory of perturbations utilizing advanced basis set. Nonlinear complexes are stabilized by the basic C-H center dot center dot center dot F interaction and additionally by van der Waals-type C-D-F center dot center dot center dot C contacts between deuterated methyl fluoride and fluoroform. (C) 2018 Elsevier B.V. All rights reserved.

In this work correlation dependencies between hydrogen bond energy LIE for complexes with F-H center dot center dot center dot F hydrogen bond and their spectroscopic characteristics of the IR and NMR spectra are presented. We considered 26 complexes in a wide hydrogen bond energy range 0.2-47 kcal/mol. For each complex we calculated complexation energy (MP2/6-311++G(d,p)), IR spectroscopic parameters (FH stretching frequency nu, FH stretching frequency in local mode approximation vim at MP2/6-311++G(d,p) level) and NMR parameters (chemical shift of hydrogen delta H and fluorine nuclei delta F, Nuclear Independent Chemical. Shielding and spin -spin coupling constants (1)J(FH), (1h)J(H...F) (2h)J(FF) B3LYP/pcSseg-2 level). It was shown that changes of parameters upon complexation, i.e. changes of the stretching frequency in local mode approximation Delta nu(LM), change of the proton chemical shift Delta delta H and change of the absolute value of spin spin coupling constant 1,(1)J(FH) could be used for estimation of corresponding hydrogen bond strength. Furthermore, we build correlation dependencies between abovementioned spectroscopic characteristics and geometric ones, such as the asymmetry of bridging proton position q1 =0.5.(rFH-rH...F) (C) 2018 Elsevier B.V. All rights reserved.