Infrared matrix isolation studies of complexes formed between dimethylsulfide, dimethyldisulfide and nitrous acid

The complexes formed by dimethylsulphide (DMS) and dimethyldisulphide (DMDS) with two isomers of nitrous acid have been observed, and characterised in argon and nitrogen matrices. The ν₁ OH stretching vibration of the perturbed trans-HONO monomer is 425 and 294 cm⁻¹ red shifted, respectively, for the DMS and DMDS complex in solid argon, and 441 and 301 cm⁻¹ in solid nitrogen. A large blue shift is also observed for the ν₃ NOH in-plane deformation mode: 101 and 80 cm⁻¹ for DMS–HONO-trans in argon and nitrogen matrices and 46 cm⁻¹ for DMDS–HONO-trans in nitrogen matrix. The results indicate formation of strong hydrogen bonds in the studied DMS–HONO and DMDS–HONO systems. The origin of the complicated shape of the ν₁ OH absorption is discussed. Similarities and differences between argon and nitrogen matrices are considered.     

The interaction of formohydroxamic acid with nitrogen: FTIR matrix isolation and ab initio studies

Argon matrix infrared spectra of the complexes formed between formohydroxamic acid, HCONHOH (FHA) and nitrogen have been recorded. The experimental results indicate formation of two isomeric complexes in which the nitrogen atom of the N₂ molecule is attached to the NH or OH groups of FHA. Theoretical studies of the structure and spectral characteristics of the complexes were carried out on the MP2 level with the 6-311++G(2d,2p) basis set. The calculated vibrational frequencies for the complexes present in the matrices are in good agreement with the experimental data.     

Matrix isolation infrared spectroscopic and theoretical study of noble gas coordinated dipalladium–dioxygen complexes

The reaction products of palladium atoms with molecular oxygen in solid argon have been investigated using matrix isolation infrared absorption spectroscopy and quantum chemical calculations. In addition to the previously reported mononuclear palladium–dioxygen complexes: Pd(η²–O₂) and Pd(η²–O₂)₂, dinuclear palladium–dioxygen complexes: Pd₂(η²–O₂) and Pd₂(η²–O₂)₂ were formed under visible light irradiation and were identified on the basis of isotopic substitution and theoretical calculations. In addition, experiments doped with xenon in argon coupled with theoretical calculations suggest that the Pd(η²–O₂), Pd₂(η²–O₂) and Pd₂(η²–O₂)₂ complexes are coordinated by two argon or xenon atoms in solid argon matrix, and therefore, should be regarded as the Pd(η²–O₂)(Ng)₂, Pd₂(η²–O₂)(Ng)₂ and Pd₂(η²–O₂)₂(Ng)₂ (NgAr or Xe) complexes isolated in solid argon.     

Matrix isolation infrared spectroscopic investigation of the coordination chemistry and reactivity of OVF3

The matrix isolation technique has been combined with infrared spectroscopy to identify and characterize the product of the codeposition of OVF₃ with NH₃ and with a series of nitrogen and oxygen donor bases into argon matrices at 14 K. This codeposition led to the formation of the isolated 1:1 complexes between OVF₃ and these bases. Each complex was characterized spectroscopically, including strong shifts to the V–F stretching modes, and a lesser shift to the V=O stretching mode. Numerous perturbed vibrational modes of the base subunits were noted, including a strong, 230 cm⁻¹ blue shift to the symmetric bending mode of NH₃. The magnitudes of these shifts indicate that OVF₃ is a moderate strength Lewis acid. However, in contrast to analogous reactions with OVCl₃, no further thermal or photochemical transformations of the complex occurred. Theoretical calculations were also carried out in support of the experimental work.     

Matrix isolation and theoretical study of the photochemical reaction of CH3CN with CrO2Cl2 and OVCl3

The matrix isolation technique has been combined with theoretical calculations to identify and characterize the photoproducts in the reactions of CH₃CN with CrCl₂O₂ and OVCl₃. Twin jet co-deposition of these reagents led to the formation of a 1:1 molecular complex which was observed using UV/visible spectroscopy. Irradiation of these matrices with light of λ>300 nm led to the observation of new bands in the infrared spectra, the most intense of which was seen at 1942 cm⁻¹ for the CrCl₂O₂/CH₃CN system. The product bands are assigned to the ²η complexes of acetonitrile n-oxide with CrCl₂O and VCl₃, respectively. Identification of these species was supported by extensive isotopic labeling (²H and ¹⁵N), as well as by B3LYP/6-311++G(d,2p) density functional calculations.     

N-Hydroxyurea dimers: A matrix isolation and theoretical study

The dimerization of N-hydroxyurea (NH₂CONHOH) has been investigated by FTIR matrix isolation spectroscopy and DFT(B3LYP)/6-311++G(2d,2p) calculations. The analysis of NH₂CONHOH/Ar matrix spectra and comparison with theoretical ones reveal the formation of two types of dimers with a strong OH⋯O hydrogen bond. There is an additional weak interaction between the oxygen atom of the OH group of the proton donor molecule and the NH or NH₂ group of the proton acceptor in both dimers, respectively. The identified structures correspond to local minima on the PES. The formation of the less stable structures not the most stable ones indicates that the creation of N-hydroxyurea dimers is related to the dipole-dipole interaction at the initial stage of the dimerization process, which favours generation of polar dimers.     

Matrix isolation study of the thermal and photochemical reaction of ozone with Trimethyl Indium

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH₃)₃In with O₃ over a range of time scales. Upon twin jet deposition (short reaction time), formation of the novel H₃COIn(CH₃)₂ species along with a low yield of CH₂O was observed. Subsequent UV irradiation greatly increased the yield of H₃COIn(CH₃)₂ while the intensities of the CH₂O bands were not affected. An extensive set of bands were seen for H₃COIn(CH₃)₂ after irradiation and ¹⁸O spectroscopic data was obtained as well. The identification of this species was supported by theoretical calculations at the B3LYP/lanl2dz and B3LYP/dgdzvp levels of theory. Merged jet deposition (longer reaction times) led to high yield of H₂CO, CH₃OH and C₂H₆, identifications that were confirmed by ¹⁸O substitution. Mechanistic inferences for the initial steps of this reaction are discussed.     

Matrix isolation study of the photochemical reaction of cyclohexane and cyclohexene with CrCl2O2

The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of cyclohexane and cyclohexene with CrCl₂O₂. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of λ > 300 nm. The irradiation was shown to lead to oxygen atom transfer, forming complexes between cyclic alcohol derivatives and CrCl₂O, although complexes between ring expansion products and CrCl₂O could not be ruled out. This latter result could arise from C-C bond activation and oxygen atom insertion into a C-C bond. For the cyclohexene system, the cyclohexanone-CrCl₂O complex was also observed. The identification of the complexes was further supported by isotopic labeling (²H) and by density functional calculations at the B3LYP/6-311G++(d,2p) level.     

Matrix IR studies on hydrogen-bonded complexes of hydrogen chloride and hydrogen bromide with ketene

Infrared spectra of matrices codeposited Ar/HX (X=Cl, Br) with Ar/H₂CCO mixtures have been examined. Isotopic substitutions (HX, DX, H₂CCO, D₂CCO) showed that ketene formed the 1:1 hydrogen-bonded complex with HX. The HX stretching modes were observed at 2684 cm⁻¹ in the H₂CCO–HCl complex and at 2384 cm⁻¹ in the H₂CCO–HBr complex. The ν₁ modes of the ketene submolecules were shifted to low frequency and the ν₉ modes to high frequency. It was proposed for the structure of the complex that the acid proton is bonded to the C=C pi electron system.     

Matrix isolation and ab initio studies of the H2S---CO complex

The structure, energetics, and vibrational properties of complexes formed between H₂S and CO have been investigated by matrix isolation FTIR spectroscopy and ab initio molecular orbital theory. Two stable computational minima were found representing nearly linear hydrogen bonds between the subunits. The H₂S---CO and H₂S---OC species were calculated to be bound by 5.22 and 1.54 kJ mol⁻¹, respectively. The computational results were reproduced by experimental assignments for the carbon attached complex. The stretching vibrations of the complex subunits were found to be similarly perturbed upon complexation both experimentally and computationally.     

Infrared and ab initio studies of hydrogen bonding and proton transfer in the complexes formed by pyrazoles

The results of experimental studies and quantum mechanical calculations of vibrational spectra and structure of hydrogen bonded complexes formed by pyrazole (P) and 3,5-dimethylpyrazole (DMP) are presented. IR spectra of pyrazoles in solutions, gas phase, and solid state have been investigated in wide range of concentrations and temperatures. It has been found that in the gas phase both P and DMP reveal the equilibrium between monomers, dimers, and trimers. In solutions the equilibrium between monomers and trimers dominates, no bands, which can be attributed to dimers were detected. DMP retains the trimer structure in solid state, while in the case of pyrazole P, formation of the crystal provides another type of association. Geometrical and spectral characteristics of dimers and trimers, obtained by ab initio calculations, are presented and compared with experimental data.

IR spectra of solutions containing P and DMP with a number of acids (acetic and trifluoroacetic acids, pentachlorophenol, HBr) have been studied in parallel with ab initio calculations. It has been found that pentachlorophenol forms with pyrazoles complexes with one strong hydrogen bond O–HN, while NH pyrazole group remains unbonded. With carboxylic acids DMP forms 1:1 cyclic complexes with two hydrogen bonds. In the case of acetic acid, the complex in CH₂Cl₂ solution reveals molecular structure with OHN and C=OHN bonds, in accordance with results of the calculations. For trifluoroacetic acid, the calculations predict the molecular structure to be energetically more stable in the case of the isolated binary complex (in gas phase), while the experimental spectrum of CH₂Cl₂ solution gives an evidence of the proton transfer with formation of the cyclic ionic pair with two NH⁺O⁻ bonds. The agreement with experimental results can be improved by taking into account the influence of environment in the framework of Onsager or Tomasi models. The shape of proton potential function of the complexes and medium effect on its parameters, resulted from experimental data and calculations, are discussed. It has been found that the number of potential minima and their relative depth depend strongly on the method of calculations and the basic set. Under excess of trifluoroacetic acid, the formation of 2:1 acid–DMP complex has been detected. Spectral characteristics and results of calculations point to the cyclic structure of this complex, which includes homoconjugated bis-trifluoroacetate anion and DMPH⁺ cation. With HBr both studied pyrazoles were found to form ionic complexes including one or two pyrazole molecules per one acid molecule and correspondingly monocation or homoconjugated cation BHB⁺.     

Experimental infrared spectra of matrix isolated complexes of HCl with 4-substituted pyridines. Evaluation of anharmonicity and matrix effects using data from ab initio calculations

Infrared spectra have been measured for HCl complexes with 4-cyanopyridine, 4-chloropyridine, pyridine and 4-methylpyridine isolated in argon and nitrogen matrices at about 12 K. The experimental spectra are dramatically different from computed MP2/6-31+G(d,p) harmonic spectra, a consequence of the anharmonicity of the potential energy surface in the hydrogen-bonding region. Comparisons of computed and experimental data suggest that the experimental spectra correspond to complexes with HCl distances that are much longer than the computed equilibrium distances. These longer distances, R_cor(HCl), are related to the average HCl distance in the ground vibrational state of the proton-stretching mode. The value of R_cor(HCl) determines values of three effective anharmonic force constants for the HCl stretch, the NH stretch and the coupling between them for each complex. The simulated anharmonic spectra obtained when these anharmonic force constants are used in place of the corresponding harmonic constants show spectral patterns with respect to both frequencies and intensities that are very similar to those observed in the experimental spectra obtained in Ar and N₂ matrices. 1D anharmonic potential curves related to the experimental spectra are presented. They provide insight into anharmonicity of the hydrogen-bonded proton stretch for these systems, and into the sensitivity of the potential energy surface to the environment.     

肉豆蔻酸和棕榈酸酸盐体系的振动光谱研究

报道了肉豆蔻酸和榈酸酸盐体系的振动光谱，结果表明，脂肪酸与其碱金属盐之间通过氢键和羧基配位形成酸盐络合物。酸盐体系中氢键具有不同于普通氢键的性质，本文结合振动光谱讨论了酸盐的结构和氢键性质。     

Ab initio molecular orbital calculations of the infrared spectra of hydrogen-bonded complexes of water,ammonia and hydroxylamine

Summary The geometries of three hydrogen-bonded dimers of hydroxylamine have been optimized, at the MP2 level of theory, using the 6-31G** basis set. These calculations yielded three separate local minima on the dimer potential energy surface. The interaction energies of these three species have been calculated, and corrected for basis set superposition error. The infrared band wavenumbers and intensities have been computed, and the monomer-dimer wavenumber shifts and intensity enhancements rationalized in terms of the types and strengths of hydrogen bonds present. The predicted wavenumbers have been correlated with those measured in a recent matrix isolation spectroscopic study, and an argument for the structure of the preferred dimer has been presented.     

Matrix isolation study of the reaction of dimethyl sulfoxide with CrCl2O2 and OVCl3

The matrix isolation technique, combined with infrared spectroscopy and theoretical calculations, has been employed to investigate the thermal and photochemical reactions of dimethylsulfoxide (DMSO) with CrCl₂O₂ and OVCl₃. Twin jet codeposition leads to formation and isolation of a photochemically unstable 1:1 complex. The photoproduct in the twin jet DMSO + CrCl₂O₂ experiments is identified as dimethyl sulfone, (CH₃)₂SO₂, interacting with the Cl₂CrO fragment, while in the analogous OVCl₃ reaction, the photoproduct bands were too weak to allow product identification. Merged jet codeposition led to rapid gas phase reaction, and in the case of DMSO + CrCl₂O₂, dimethyl sulfone is formed in high yield. This marks the first demonstration of a gas phase thermal oxygen atom transfer from CrCl₂O₂ to an organic substrate. For the reaction of DMSO with OVCl₃, no volatile products are deposited in the matrix and dimethyl sulfone is not a product. These results support differing pathways for the reactions of CrCl₂O₂ and OVCl₃, a conclusion that is supported by density functional calculations.     

Fourier-transform infrared spectroscopic studies of dithia tetraphenylporphine

We present here infrared absorption spectra of dithia tetraphenylporphine and its cation in the 450–1600 and 2900–3400 cm⁻¹ regions. Most of the allowed IR bands are observed in pairs due to overallD _2h point group symmetry of the molecule. The observed bands have been assigned to the porphyrin skeleton and phenyl ring modes. Some weak bands, which are forbidden underD _2h , also appear in the spectra due to the distortion of the molecule from planarity-caused by the out-of-plane positioned N and S atoms. Increased intensity of some phenyl ring bands compared to free-base tetraphenylporphine is explained on the basis of rotation of phenyl rings towards the mean molecular plane. Contrary to the point group symmetry of cation of dithia tetraphenylporphine, certain bands are observed to be degenerate due to identical bonding arrangements in pyrrole rings of the cation     

FTIR studies of the CH3CN–BF3 complex in solid Ar, N2, and Xe: Matrix effects on vibrational spectra

FTIR spectra of the four isotopically substituted 1:1 complexes of acetonitrile and boron trifluoride were recorded in Ar, N₂ and Xe matrices. In Ar, previously unreported three vibrational modes of the complex were clearly observed. Several significant vibrational bands were also observed in N₂ and Xe. The observed frequency shifts on complexation, Δν, were qualitatively in good agreement with the computational results, which were calculated at the B3LYP/6-311++G(d,p) level using the optimized geometry of the C_3v eclipsed conformation. The observed magnitudes of Δν for most of the complex bands were larger than the calculated values. The BF₃ symmetric deformation mode is an exception. The observed frequency shits for this mode were smaller than the calculated values, especially in N₂. This suggests that even an inert matrix can significantly affect the vibrational spectrum of the complex.     

Matrix isolation infrared spectra of the complexes between methylacetate and water or hydrochloric acid

The hydrogen-bonded complexes between methylacetate (MeAc) and water or hydrochloric acid have been studied by infrared spectrometry in a low temperature Argon matrix. The ν_CO, ν_CC and ν_CC ional modes of MeAc show a splitting to the low and to the high frequency side of the free molecule. This suggests that water and HCl interact with the keto and ether oxygens. This conclusions is supported by the appearance of two main absorptions in the ν_HCl region. These results are discussed as a function of the gas-phase basicity of the two oxygen atoms, derived from the O(1s) core electron binding energies and from the ionization potentials.