Infrared matrix isolation study of the reaction of CrCl2O2 with (CH3)2O and (CH3)2CO

Matrix isolation has been combined with infrared spectroscopy to study the reaction chemistry of CrCl₂O₂ with (CH₃)₂O and (CH₃)₂CO. Very similar results were obtained with twin jet and room temperature merged jet deposition, indicating that the initial product forms on the surface of the matrix during deposition, not in the deposition lines prior to matrix condensation. The initial product in both systems was identified as the 1:1 complex between the two reagents, with a structure in which the oxygen atom of the base donates electron density to the Cr center. A number of perturbed vibrational modes of both subunits were observed; for the bases, these modes were vibrations involving the oxygen atom. Hg arc irradiation of the CrCl₂O₂·O(CH₃)₂ complex led to growth of a secondary product that is tentatively identified as Cl₂CrO(OCH₃)₂. The CrCl₂O₂·OC(CH₃)₂ complex was not photosensitive, and no rearrangements were observed.     

Coordination of niobium and tantalum oxides by Ar, Xe and O2: Matrix isolation infrared spectroscopic and theoretical study of NbO2(Ng)2 (Ng = Ar, Xe) and MO4(X) (M = Nb, Ta; X = Ar, Xe, O2) in solid argon

The combination of matrix isolation infrared spectroscopic and quantum chemical calculation results indicate that the NbO₂ molecule is coordinated by two noble gas atoms in forming the NbO₂(Ng)₂ (Ng = Ar, Xe) complexes in solid noble gas matrixes. In contrast, the TaO₂ molecule is not able to form similar noble gas complex. The niobium and tantalum dioxides further react with dioxygen to form the side-on bonded superoxo-dioxide complexes MO₄ (M = Nb, Ta), which are coordinated by one argon atom in solid argon matrix. The coordinated Ar atom in MO₄(Ar) can be replaced by O₂ or Xe in forming the MO₆ and MO₄(Xe) complexes. The results indicate that the NbO₂, NbO₄ and TaO₄ molecules trapped in solid noble gas matrixes should be regarded as the NbO₂(Ng)₂ and MO₄(Ng) (Ng = Ar, Xe; M = Nb, Ta) complexes instead of “isolated” metal oxide species.     

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.     

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.     

An ab initio and matrix isolation infrared study of the 1:1 C2H2–CHCl3 adduct

The details of weak C–Hπ interactions that control several inter and intramolecular structures have been studied experimentally and theoretically for the 1:1 C₂H₂–CHCl₃ adduct. The adduct was generated by depositing acetylene and chloroform in an argon matrix and a 1:1 complex of these species was identified using infrared spectroscopy. Formation of the adduct was evidenced by shifts in the vibrational frequencies compared to C₂H₂ and CHCl₃ species. The molecular structure, vibrational frequencies and stabilization energies of the complex were predicted at the MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels. Both the computational and experimental data indicate that the C₂H₂–CHCl₃ complex has a weak hydrogen bond involving a C–Hπ interaction, where the C₂H₂ acts as a proton acceptor and the CHCl₃ as the proton donor. In addition, there also appears to be a secondary interaction between one of the chlorine atoms of CHCl₃ and a hydrogen in C₂H₂. The combination of the C–Hπ interaction and the secondary ClH interaction determines the structure and the energetics of the C₂H₂–CHCl₃ complex. In addition to the vibrational assignments for the C₂H₂–CHCl₃ complex we have also observed and assigned features owing to the proton accepting C₂H₂ submolecule in the acetylene dimer.     

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.     

Infrared spectra of (CH3)2O and (CH3)2O + H2O at low temperature

Fourier transform infrared reflection spectroscopy (incidence angle of 5°) was used to characterize thin films of dimethyl ether (DME) and of mixtures containing water and DME between 10 and 160 K under a pressure of 10⁻⁷ mbar. Solid DME has two solid phases: an amorphous phase which is obtained below 65 K and a crystalline phase >65 K. From 90 K, DME begins to sublimate with surface binding energy of 20±2 kJ mol⁻¹. Vibrational spectrum of DME trapped in water ice remains nearly unchanged from 30 to 120 K. Between 120 and 130 K, a large part of DME is released and strong changes in the frequencies and the profile of the absorptions of DME are observed. This behavior suggests the formation of clathrate hydrate. Below 120 K, the trapped DME is hydrogen-bonded to water molecules.     

Solvent effects on non-resonant vibrational deactivation: N2(ν = 1) deactivated by CH4 in liquid Ar/liquid N2 mixtures

New measurements have been made of rate constants for the vibrational deactivation of N₂(ν = 1) by CH₄ in liquid Ar/liquid N₂ mixtures. The ratio of the liquid phase rate constants, k_L,M for the liquid mixture over k_L,Ar for liquid argon solution, varies non-linearly with composition. The results imply a saturation effect which occurs when one solvent N₂ molecule is present in the first solvation shell of the excited molecule. It is proposed that this is due to the formation of a N₂(ν = 1) … N₂ collision complex.     

Trajectory studies of energy transfer: CH3NC with He,Xe, H2 and N2

A trajectory program was used to simulate the collisions of CH₃NC with He, Xe, H₂ and N₂. Calculated energy transfer is in accord with experiment. The pattern of CH₃NC vibrational mode energization is found to be noticeably non-random. The approximate sampling methods used in thermal unimolecular trajectory studies produce a more uniform state distribution.     

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 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.     

Novel measurements of refractive index, density and mid-infrared integrated band strengths for solid O2, N2O and NO2:N2O4 mixtures

We present novel measurements of the refractive index, density and integrated band strengths of mid-infrared features of solid N₂O at 16 K and of NO₂ and N₂O₄ in two frozen NO₂:N₂O₄ mixtures deposited at 16 and 60 K. The refractive index and density measurements were performed also for frozen O₂ deposited at 16 K. In this case, the integrated band strength values could not be determined since O₂ is a homonuclear molecule and therefore its fundamental mode is not infrared active. The solid samples were analysed by infrared spectroscopy in the 8000÷800 cm⁻¹ range. The sample thickness was measured by the interference curve obtained using a He–Ne laser operating at 543 nm. The refractive index at this laser wavelength was obtained, by numerical methods, from the measured amplitude of the interference curve. The density values were obtained using the Lorentz–Lorenz relation. Integrated band strength values were then obtained by a linear fit of the integrated band intensities plotted versus column density values. The astrophysical relevance of these novel measurements is briefly discussed.     

Electrosynthesis of highly conducting poly(1,5-dihydroxynaphthalene) in BF3·Et2O

Direct anodic oxidation of 1,5-dihydroxynaphthalene (DHN), an important derivative of naphthalene, led to the formation of high-quality semiconducting poly(1,5-dihydroxynaphthalene) (PDHN) on stainless steel sheets in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of DHN in this medium was measured to be only 0.78 V vs. SCE, which was lower than that determined in traditional acetonitrile containing 0.1 mol/L tetrabutylammonium tetrafluoroborate (0.98 V vs. SCE). As-formed PDHN films showed good redox activity and stability, together with interesting electrochromic property from brown (doped) to yellow-green (dedoped). Structural characterization, including FTIR, ¹H NMR, and quantum chemistry calculations, indicated that the polymerization of DHN probably occurred at C₄ and C₈ positions. Moreover, thermal analysis revealed that PDHN displayed better thermal stability than that synthesized by chemical method. The fluorescence spectral studies, together with the electrical tests, showed that PDHN was a good blue light-emitter (fluorescence quantum yield higher than 0.1) with an electrical conductivity of as high as 0.46 S/cm.     

Matrix isolation study of the thermal and photochemical reaction of OVCl3 and CrCl2O2 with cycloalkylamines

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to identify and characterize the initial and secondary products in the thermal and photochemical reactions of OVCl₃ and CrCl₂O₂ with cyclopropyl-, cyclobutyl- and cyclopentylamine. Initial twin jet deposition led to the formation of two new species, the 1:1 molecular complex and the secondary HCl elimination product (e.g. Cl₂V(O)N(H)C₃H₅), as well as free HCl. Overall, the yield decreased with the size of the cycloalkyl ring, to the point with cyclopentylamine, the yield was extremely low and no firm conclusions could be reached. The complexes appear to be moderately strongly bound, leading to shifts to certain vibrational modes of both the acid and base subunits. Bands due to the complexes were destroyed by near-UV irradiation and led an increase in the intensity of the bands due to the HCl elimination product, as well as cage-paired HCl. Theoretical calculations were used to aid in product identification and band assignments.     

Shake-up satellites in Hel photoelectron spectra: N2O4 and CH3O

Low-lying vacant molecular orbitals may lead not only to a breakdown of Koopmans' theorem but also to satellite structure in photoelectron spectra. This paper reports examples of the relatively infrequent appearance of shake-up satellites in Hel photoelectron spectra, namely those of N₂O₄ and CH₃NO. An extended version of the HAM/3 program was used to interpret these spectra.     

Crystal structure, magnetic and infrared spectroscopy studies of the LiCryFe1−yP2O7 solid solution

The lithium double diphosphates LiCr_yFe_1−yP₂O₇ have been investigated by X-ray diffraction, SQUID measurements and vibrational spectroscopy. The Rietveld refinements based on the XRD patterns show the existence of a continuous solid solution over the whole composition range (0?y?1.0) with a continuous evolution of the monoclinic unit cell parameters (S.G. P2₁). The transition metal ions connect the diphosphate anions forming a three-dimensional network with channels filled by Li⁺ cations expected to exhibit high mobility. All compounds order magnetically at low temperatures due the Fe-Fe interactions. The ordering temperature decreases with increasing Cr content. The slope in Curie-Weiss fits to the 1/χ vs T data in the paramagnetic domain clearly shows the existence of Fe³⁺ and Cr³⁺ in their high spin states, and a ferromagnetic component is clearly detected for y=0, 0.2 and 0.4. IR spectra have been interpreted using factor group analysis. The small shift of the frequencies is due to the influence of the chromium amount. The POP angles were estimated using the Lazarev's relationship.     

Equilibrium diagram of KPO3–Y(PO3)3 system, chemical preparation and characterization of KY(PO3)4

Microdifferential thermal analysis (μ-DTA), X-ray diffraction (XRD) and infrared (IR) spectroscopy were used for the first time to investigate the liquidus and solidus relations in the KPO₃–Y(PO₃)₃ system. The only compound observed within the system was KY(PO₃)₄ melting incongruently at 1033 K. An eutectic appears at 13.5 mol% Y(PO₃)₃ at 935 K, the peritectic occurs at 1033 K and the phase transition for potassium polyphosphate KPO₃ was observed at 725 K. Three monoclinic allotropic phases of the single crystals were obtained. KY(PO₃)₄ polyphosphate has the P2₁ space group with lattice parameters: a=7.183(4) Å, b=8.351(6) Å, c=7.983(3) Å, β=91.75(3)° and Z=2 is isostructural with KNd(PO₃)₄. The second allotropic form of KY(PO₃)₄ belongs to the P2₁/n space group with lattice parameters: a=10.835(3) Å, b=9.003(2) Å, c=10.314(1) Å, β=106.09(7)° and Z=4 and is isostructural with TlNd(PO₃)₄. The IR absorption spectra of the two forms show a chain polyphosphates structure. The last modification of KYP₄O₁₂ crystallizes in the C2/c space group with lattice parameters: a=7.825(3) Å, b=12.537(4) Å, c=10.584(2) Å, β=110.22(7)° and Z=4 is isostructural with RbNdP₄O₁₂ and contains cyclic anions. The methods of chemical preparations, the determination of crystallographic data and IR spectra for these compounds are reported.     

FTIR and computational studies of pure and water containing SO3 species in solid argon matrices

The FT infrared spectrum in the 4000–400 cm⁻¹ range of SO₃ vapors, matrix isolated in argon and in water doped argon solid layers, is reported. Vibrational bands are assigned to pure SO₃ monomeric and polymeric species and to SO₃H₂O complexes, on the basis of theoretical B3LYP and MP2 calculations employing the aug-cc-pVTZ basis sets. The spectroscopic evidence suggests that in addition to the monomer, both the dimeric and the cyclic trimeric (SO₃)_n complexes are the only other SO₃ forms present in the matrix. The spectra also indicate the presence of the 1:1 and the 1:2 SO₃·H₂O complexes as well as traces of H₂S₂O₇ and water complexed H₂SO₄, but no evidence for a stable 2:1 SO₃H₂O complex was found. The occurrence of the various species is discussed in the light of their calculated energies.     

Phase transitions in the A2BX4-compound: Tetramethylammonium tetrachlorozincate tetrachlorocuprate, [(CH3)4N]2Zn0.5Cu0.5Cl4, and room temperature crystal structure determination

Preparation, crystal structure, and infra-red absorption spectra are reported for the first material in an A₂BX₄ compound with metal transition substitution in tetrahedral anion, tetramethylammonium tetrachlorozincate tetrachlorocuprate: [(CH₃)₄N]₂Zn_0.5Cu_0.5Cl₄. The calorimetric study shows five endothermic peaks at 248.75, 271.75, 278.6, 286.7, and 293.7 K. The determination of unit cell in the 240–298 K temperature range confirms those observed by the DSC technique. At room temperature, the compound crystallizes in an orthorhombic system (P2₁ cn space group) with Z = 4 and the following unit cell dimensions: a = 8.988 (3), b = 15.527 (2) and c = 12.269 (4) ?. The structure was solved by using 1986 independent reflections down to an R value of 0.048. The crystal structure consists of alternating organic-inorganic [(TMA)⁺/(Cu)ZnCl₄²⁻] layers and organic sheets (TMA)²⁺. All Organic groups and (Cu)ZnCl₄²⁻ are not disordered. Their main geometrical features are those commonly observed in the atomic arrangements of (TMA)₂ZnCl₄ and (TMA)₂CuCl₄. The text was submitted by the authors in English.     

Synthesis, vibrational and NMR spectroscopic characterization of [N(CH3)4][IO2F2] and X-ray crystal structure of [N(CH3)4]2[IO2F2][HF2]

The salt, [N(CH₃)₄][IO₂F₂], was prepared from [N(CH₃)₄][IO₃] and 49% aqueous HF, and characterized by Raman, infrared, and ¹⁹F NMR spectroscopy. Crystals of [N(CH₃)₄]₂[IO₂F₂][HF₂] were obtained by reduction of [N(CH₃)₄][cis-IO₂F₄] in the presence of [N(CH₃)₄][F] in CH₃CN solvent and were characterized by Raman spectroscopy and single-crystal X-ray diffraction: C2/m, a = 14.6765(2) Å, b = 8.60490(10) Å, c = 13.9572(2) Å, β = 120.2040(10)°, V = 1523.35(3) Å³, Z = 4 and R = 0.0192 at 210 K. The crystal structure consists of two IO₂⁻F₂ anions that are symmetrically bridged by two H⁻F₂ anions, forming a [F₂O₂I(FHF)₂IO₂F₂]⁴⁻ dimer. The symmetric bridging coordination for the H⁻F₂ anion in this structure represents a new bonding modality for the bifluoride anion.