K.S. Rutkowski

Unusual spectroscopic properties of CF3H dissolved in liquified Ar, N2, CO, and CO2

Abstract The FTIR spectra of CF 3 H have been studied in liquefied Ar, N 2 , CO, and CO 2 . The effect of a blue shift of frequency of the C – H stretching vibration accompanied by a decrease in the integral intensity of the corresponding ν 1 band was found in the studied series of solvents. The combination bands ascribed to simultaneous excitation of vibrations of interacted molecular partners have been revealed in CO and CO 2 solutions. DFT/B3LYP and ab initio MP2 calculations utilizing the 6-311++G(3df,3pd) basis set suggest weak linear F 3 CH⋯ B complex formation, reproduce the experimentally observed unusual trends for B= Ar , N 2 , CO, CO 2 , and predict the conventional red frequency shift of the ν 1 band for B =NH 3 .

Infrared studies of weak B…HCl (B = HCl, CO, Xe, N2) complex formation in solid Kr solutions

Abstract IR spectra of small B…HCl (B = HCl, N 2 , Xe, CO) complexes have been studied in solid phase at equilibrium conditions by using the technique of crystal growth from a liquid Kr solution. Triplet to doublet structure evolution of the ν(HCl) fundamental band has been revealed at liquid to crystal state transition of the noble (Xe, Kr) gas solutions. Residual rotational structure observed at wings of the ν(HCl) band and spectral moments analysis suggest that noncomplexed HCl molecules continue to rotate in solid solutions studied. Self-association of HCl molecules has been found in solid Kr, while this process was strongly suppressed in solid Xe. Spectral parameters of the ν c fundamental bands and enthalpy of formation ΔH were estimated for B…HCl complexes in solid Kr. Comparative analysis of the ν c (CO) and ν c (HCl) bands shows that the ν c (HCl) bands is perturbed due to intermolecular H-bonding and the OC…HCl complex does not rotate in solid Kr. Relative changes of the integral intensity A of the fundamental ν c (HCl) and ν c (CO) bands due complex formation have been derived from the temperature dependence of the A value.

Higher-order transitions in the IR spectrum of the weak OC⋯HCl complex dissolved in liquid CO

Abstract Infrared spectra of HCl-doped CO solutions have been studied at T ∼140–90 K. First overtone and combination bands of the OC⋯HCl complex were revealed at the lowest temperature of the liquid solution. Ab initio calculations utilizing the 6-311++G(3df,3pd) basis set with electron correlation at the n th-order Moller–Plesset (MPn, n ⩽4) levels of approximation predict minima for the CO⋯HCl and OC⋯HCl linear structures. Based on simplified treatment of anharmonic interactions between CO and HCl constituents, the model estimations of the dipole transition moments have been performed.

Temperature dependence studies and model calculations of ν(OH) and ν(OD) band shapes of salicylaldehyde

Abstract IR spectra of salicylaldehyde (OH and OD) have been studied over a wide temperature range in teh vapor phase, liquid Xe solution and Ar matrices. Far IR and Raman spectra have been obtained. Ab initio calculations at the 3-21G∗∗ level have been performed in order to establish the geometry of the molecule, normal coordinates and frequencies of vibrations. It has been found that profiles of both ν (OH) and ν (OD) bands are formed by the fundamental transition ν s , by the weak sum transition ν s + ν 3 , where ν 3 = 264 cm −1 is an in-plane vibration involving deformation of the chelate ring with significant stretching of the intramolecular H-bond, and by a series of hot transitions from levels of ν 3 and other low frequency modes ( ν i ) of the chelate ring. The ν (OH) profile is perturbed additionally by several Fermi resonances with overtones and combinations of bending vibrations δ(OH). Anharmonicity constants, which characterize coupling of ν s with ν i and δ(OH), have been derived from the temperature dependence of the first spectral moments of the bands, using the results of the 3-21G∗∗ treatment. Model calculations of ν (OH) and ν (OD) band shapes have been performed.

Vibrational spectra of OC⋯HCl complex in Kr solutions at liquid to solid phase transition

Abstract Fundamental and first overtone bands of HCl, CO molecules and OC⋯HCl complex were studied in liquid and solid Kr solution near the phase transition. Triplet to doublet shape transformations were observed for both fundamental ν (HCl) and first overtone 2 ν (HCl) bands at liquid to crystal state transition. Self-association processes of HCl in Kr solutions have resulted in the registration of two to several new sharp peaks on the low frequency P branch of the ν (HCl) band, whereas they only gave an additional diffuse absorption on the P branch of the 2 ν (HCl) band. Evolution of the ν (CO) and 2 ν (CO) bands, observed at temperature lowering of liquid Kr solution, has shown an increased restriction of the rotational motion of CO in an orienting field of the nearest neighbors. Triplet to singlet shape transformation was found for both the CO bands at liquid to crystal state transition. Asymmetry of the central parts of the bands and high frequency shoulder, which are increased at temperature lowering of the solids, suggest the consecutive transformation of orientational motion of CO into libration and growth of vibrational–translational coupling in CO doped low temperature Kr crystal. OC⋯HCl complex formation with a weak intermolecular H-bond were studied by observation of the red shifted ν c (HCl) band and of the blue shifted ν c (CO) and 2 ν c (CO) sharp bands in the solid state. Spectral parameters of dimer bands were estimated.

Investigation of the IR spectra of weakly hydrogen-bonded complex Cl3CH…O(CD3)2 in a cryosolution in liquid krypton

The IR absorption spectra of cryosolutions of chloroform, dimethyl ether, and their mixtures in liquefied krypton have been measured. It has been shown that, in solutions of mixtures, Cl3CH…O(CD3)2 complexes with a weak hydrogen bond are formed. The spectral characteristics of individual absorption bands that refer to proton donors and to proton acceptors have been determined. From temperature measurements of the integrated intensities of the bands of monomers and of the complex (T ~ 120–160 K), the enthalpy of the complex formation has been estimated. The measurement data have been analyzed in comparison with the results of ab initio calculations in terms of the МР2/6-311++G(2df, 2pd) approximation. The analysis has been done taking into account peculiarities of the dipole moment function of chloroform and possible effects of the anharmonic interaction between the С–Н stretching vibration and the overtone of the Cl–C–H bending vibration.

Infrared studies of CO2 doped Xe solutions in gas, liquid and solid phases. The fundamental ν3 band and the Coriolis perturbed Fermi doublet (ν1+ν21, ν1+ν211)

Abstract The IR absorption spectra of CO 2 doped Xe solutions have been recorded in the range of the fundamental ν 3 (Σ u ) band and of the Coriolis perturbed ν 1 + ν 2 1 , ν 1 + ν 2 11 (π u ) Fermi doublet ( ν 1 + ν 2 ≈3 ν 2 ) in gas, liquid and solid phases. The characteristic transformation and rapid narrowing of the ν 3 band, observed in the gas to liquid phase transition, shows marked hindering of the rotational motion of the CO 2 molecule in dense Xe mixtures. It was found that the liquid to solid phase transition is accompanied by noticeable broadening of the ν 3 band. The rotational motion of CO 2 is not frozen in solid Xe at least near the freezing point. This is in contrast with sharp narrowing of the vibrational bands and so with blocking up rotations in the case of a heavier CS 2 guest in the solid Xe host just below the freezing point. The intensity ratio A ( ν 1 + ν 2 1 )/ A ( ν 1 + ν 2 11 ) of the Coriolis perturbed ν 1 + ν 2 1 , ν 1 + ν 2 11 doublet reveals the noticeable increase from 8±1 in a low density gas to 18±2 in the liquid phase. The results obtained suggest remarkable modification of the second-order Coriolis coupling in the case of CO 2 doped dense liquid Xe.

The infrared study of fluoroform + methyl fluoride mixtures in argon and nitrogen matrices. Evidence of nonlinear blue-shifting complex formation

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 CH⋯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 Møller-Plesset theory of perturbations utilizing advanced basis set. Nonlinear complexes are stabilized by the basic CH⋯F interaction and additionally by van der Waals-type CD⋯FC contacts between deuterated methyl fluoride and fluoroform.

FTIR cryospectroscopic and ab initio studies of desflurane–dimethyl ether H–bonded complexes

The IR spectra of mixtures of desflurane and dimethyl ether are studied with the help of FTIR cryospectroscopy in liquefied Kr at T~118-158K. Comparative analysis of the experimental data and results of ab initio calculations show that either of the two C-H groups of desflurane is involved in heterodimer formation of comparable strengths. The blue frequency shift is found for stretching vibrations of those C-H donors which directly participate in H-bond formation. Additionally the complexes are stabilized by weaker contacts between hydrogen atoms of dimethyl ether and fluorine atoms of desflurane.

IR spectra of halothane–acetone complex in liquefied noble gases (Kr and Xe)

IR absorption spectra of solutions of halothane (C2HBrClF3) and acetone ((CD3)2CO) mixtures in liquefied noble gases (krypton and xenon) have been recorded and analyzed. Bands due to weak hydrogenbonded complexes are identified. The complex-formation enthalpy is estimated in a series of temperature experiments on the change in the total intensity of the bands due to monomers and complexes. Second-order bands are found, which are assigned to the first overtone of stretching vibration CH of halothane and the Raman band related to simultaneous excitation of stretching vibration CH of halothane and stretching vibration CO of acetone. The results of ab initio calculation performed within the МР2/6-311++G(d, p) approximation are used to analyze the spectroscopic data.