The gas-phase on-line production of vanadium oxytrihalides, VOX3 and their identification by infrared spectroscopy

A new route has been devised, leading to the production of VOX3 molecules where X=F, Br and I by an on-line process using vanadium oxytrichloride, VOCl3 as a starting compound passed over the following heated salts NaF, KBr and KI at 375, 700 and 550 degrees C, respectively. The products have been characterized by the IR spectra of their vapors. The low resolution gas phase on-line Fourier transform infrared spectra reported for the first time show strong bands with PQR type structure, centered at 1058, 1035, 1030 and 1025 cm(-1) assigned to the v1(a1), the O=V stretching fundamental mode of VOF3, VOCl3 VOBr3 and VOI3, respectively.     

The gas-phase on-line production of phosphorus thiotrihalides,SPX3 and their identification by infrared spectroscopy

A new route has been devised, leading to the production of phosphorus thiotrihalides, SPX3 where X = F, Br and I by an on-line process using phosphorus thiotrichloride, SPCl3 as starting compound gassed over the following heated salts NaF, KBr and KI at 530, 800 and 440 degrees C, respectively. The products have been characterized by their IR spectra, showing bands with PQR type structure, centered at 985, 762, 744 and 715 cm(-1). These bands are assigned to v1(a1), the S=P stretching fundamental modes of SPF3, SPCl3, SPBr3 and SPI3, respectively.     

The infrared and Raman spectra, ab initio calculations and spectral assignments of cyclopropylmethyl dichlorosilane (c-C3H5)SiCl2CH3

Raman spectra of cyclopropylmethyl dichlorosilane (c-C₃H₅)SiCl₂CH₃ as a liquid were recorded at 293 K and polarization data were obtained. Additional Raman spectra were recorded at various temperatures between 293 and 163 K, and intensity changes of certain bands with temperature were detected. No crystallization was ever obtained in the Raman cryostat in spite of extensive annealing. The infrared spectra have been studied as a vapour, as an amorphous solid at 78 K and as a liquid in the range 600-100 cm⁻¹. No infrared bands present in the vapour or liquid seemed to vanish upon cooling, and the sample never formed crystals on the CsI window of an infrared cryostat.The compound exists a priori in two conformers, syn and gauche, and the experimental results suggest an equilibrium in which the gauche conformer has 1.64 kJ mol⁻¹ lower enthalpy than syn in the liquid, leading to 20% syn at ambient temperature. Most of the syn bands were situated close to the corresponding gauche bands and it was difficult to obtain reliable ΔH values.B3LYP calculations with various basis sets and the CBS-QB3 and G2 and G3 models were employed, yielding the conformational enthalpy difference ΔH (syn-gauche) between 2.6 and 3.4 kJ mol⁻¹. Infrared and Raman intensities, polarization ratios and vibrational frequencies for the syn and gauche conformers were calculated. Instead of scaling the calculated wavenumbers in the harmonic approximation, calculations from B3LYP/cc-pVTZ were derived in the anharmonic approximation. In most cases these values were in good agreement with the experimental results for 38 observed modes of the gauche and 8 modes of the syn conformer with a deviation of ca. 1%.     

The role of TiO2 in the B2O3–Na2O–PbO–Al2O3 glass system

Optical and vibrational studies have been carried out on 60B₂O₃·(20−x)Na₂O·10PbO·10Al₂O₃:xTiO₂ (x=0, 1, 2, 3, 4, and 5 mol%) glasses, in order to understand the role of TiO₂ in the 60B₂O₃·20Na₂O·10PbO·10Al₂O₃ glass matrix. The X-ray patterns reveal homogeneous glasses over the entire compositional range. The absorption spectra show that the energy of the optical band gap (ΔE_opt) and Urbach's energy (E_U) decreases as TiO₂ content increases. The changes observed in the Raman and IR spectra are related to the BO₄→BO₃ back conversion effect and the appearance of “loose” BO₄⁻ groups. The data indicate that titanium ions act as a network modifier.     

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.     

The gas-phase on-line formation of antimony oxide trihalides, SbOX3 where X = F and Cl and their identifications by infrared spectroscopy

Antimony oxide trihalides, SbOX3 molecules, where X = F or Cl have been produced, by means of an on-line process, using antimony trichloride, SbOCl3 as starting material passed over heated silver oxide at 230 degrees C. The antimony oxide trichloride SbOCl3 formed is then reacted with sodium fluoride, NaF at 550 degrees C to produce antimony oxide trifluoride, SbOF3. The products have been characterized by the IR spectra of their vapors. Low resolution gas-phase Fourier transform infrared spectra show strong bands centered at 1272 and 1217 cm(-1), assigned to nu1(a1), the O=Sb stretching fundamental of SbOF3 and SbOCl3, respectively. Both observed bands show typical PQR-type structure with a strong Q-head.     

Hydrothermal synthesis and structure characterization of a new 3D vanadium hydrogen phosphite with 14-ring channels: (C5N2H14)[VO(H2O)]3(HPO3)4·H2O

A new 3D vanadium hydrogen phosphite, (C₅N₂H₁₄)[VO(H₂O)]₃(HPO₃)₄·H₂O, has been prepared by hydrothermal reactions and characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and magnetic techniques. It crystallizes in the triclinic space group P-1 (no. 2) with , , , α=76.124(3)°, β=83.726(4)^o, γ=75.222(4)^o, Z=2. The structure is built up from sharing equatorial oxygen atoms of VO₅(H₂O) octahedra with HPO₃ tetrahedra, which can be viewed as a (3,4) connected net. The framework is mainly constructed by two types of four-ring related chains. Intrachain and interchain hydrogen bonds play an important role on supporting the framework structure. The 14-ring tunnels in the structure are filled with 1-methypiperazinium and water molecules, which also contribute the hydrogen bonding with the vanadium phosphite framework.     

Equilibrium bond lengths, force constants and vibrational frequencies of MnF2, FeF2, CoF2, NiF2, and ZnF2 from least-squares analysis of gas-phase electron diffraction data

The least-squares analysis of the electron diffraction data for MnF₂, FeF₂, CoF₂, NiF₂ and ZnF₂ was carried out in terms of a cubic potential function. The obtained equilibrium bond lengths (in Å) are r_e(Mn–F)=1.797(6), r_e(Fe–F)=1.755(6), r_e(Co–F)=1.738(6), r_e(Ni–F)=1.715(7), and r_e(Zn–F)=1.729(7). The determined force constants and the corresponding vibrational frequencies are listed. The bond length r_e(Cu–F)=1.700(14) Å for CuF₂ was estimated and the variations of bond lengths for the first-row transition metal difluorides were discussed in light of their electronic structure.     

Hydrothermal synthesis and characterization of a new 3D vanadium(III) phosphite (C4H8N2H4)0.5(C4H8N2H3)[V4(HPO3)7(H2O)3]1.5H2O

A new vanadium(III) phosphite, (C₄H₈N₂H₄)_0.5(C₄H₈N₂H₃)[V₄(HPO₃)₇(H₂O)₃]1.5H₂O, has been synthesized hydrothermally by using V₂O₅, H₃PO₃ as reactants, piperazine as the structure-directing agent. The as-synthesized product was characterized by powder X-ray diffraction, IR spectroscopy, inductively coupled plasma analysis, thermogravimetric analysis, and SQUID magnetometer. Single-crystal X-ray diffraction analysis shows that the title compound crystallized in the trigonal space group (No. 165) with the parameters: , , and Z=4. Its structure is built up by alternation of octahedral VO₆ or VO₅(H₂O) and pseudo-pyramidal HPO₃ units to form infinite 2D layers, and these layers are interconnected by sharing vertex-oxygen with octahedral VO₆ units to generate a 3D open-framework structure with 12-membered ring channels in a and b directions, respectively, where there exist entrapped diprotonated and mono-protonated piperazine cations, and water molecules. Magnetic measurement indicates that paramagnetic behavior is observed down to 4 K.     

The niobium and tantalum riddle: gas-phase monocation reactions with pyrene and pyrene-D10

Metal monocation gas-phase reactions with pyrene (Py) have been investigated. Of those cations which bind Py by abstraction of two hydrogen atoms, there are two subgroups of which Nb⁺ and Ta⁺ are the most striking and puzzling representatives. The Ta⁺-like group binds three Py units consecutively, each by expulsion of two hydrogen atoms, whereas the Nb⁺ group binds four Py units; however, in this latter case, the second Py attachment occurs without the expulsion of any hydrogen. When perdeuterated Py-D₁₀ is used, the Ta⁺ group behavior is unaffected, but the Nb⁺ group now exhibits a considerable degree of Py attachment in which no deuterium atoms are lost in the first reaction step. We will attempt to explain this behavior by using the results of reactions of Nb⁺ and Ta⁺ with Py in a Fourier transform mass spectrometer (FTMS).     

Hydrothermal synthesis and characterization of layered vanadium phosphite: [HN(C2H4)3N][(VO)2(HPO3)2(OH)(H2O)]·H2O

A novel compound, [HN(C₂H₄)₃N][(VO)₂(HPO₃)₂(OH)(H₂O)]·H₂O, was hydrothermally synthesized and characterized by single crystal X-ray diffraction. This compound crystallizes in the monoclinic system with the space group C2/c and cell parameters a=11.0753(3) Å, b=17.8265(6) Å, c=16.5229(5) Å, and β=92.362(2)°. The structure of the compound consists of vanadium phosphite layers which are built up from the infinite one-dimensional chains of [(VO)(H₂O)(HPO₃)₂]²⁻ of octahedral VO₅(H₂O) and pseudo pyramidal [HPO₃], and bridging binuclear fragments of [VO(OH)]₂. Thermogravimetric analysis and magnetic susceptibility data for this compound are given.     

Hydrothermal syntheses and structures of two novel vanadium selenites, {[VO(OH)(H2O)](SeO3)}4·2H2O and (H3NCH2CH2NH3)[(VO)(SeO3)2]

Two novel vanadium selenites {[VO(OH)(H₂O)](SeO₃)}₄·2H₂O 1 and (H₃NCH₂CH₂NH₃)[(VO)(SeO₃)₂] 2 were synthesized by hydrothermal method and their crystal structures were determined by single-crystal X-ray diffraction. It is characterized by inductively coupled plasma (ICP), thermogravimetric (TG) and elemental analyses. Compound 1 crystallizes in the monoclinic system, space group C2/c, a=21.2250(11) Å, b=12.6309(6) Å, c=17.0249(10) Å, β=96.830(3)°, V=4531.8(4) Å³ and Z=8, R₁ [I>2σ(I)]=0.0344, wR₂ [I>2σ(I)]=0.119; Compound 2 crystallizes in the monoclinic system, space group P2₁/c, a=9.6389(4) Å, b=6.9922(3) Å, c=15.0324(5) Å, β=102.297(2)°, V=989.90(7) Å³ and Z=4, R₁ [I>2σ(I)]=0.0452, wR₂ [I>2σ(I)]=0.117. {[VO(OH)(H₂O)](SeO₃)}₄·2H₂O has a 1D structure constructed from the {[VO(OH)(H₂O)](SeO₃)}_∞ chains. (H₃NCH₂CH₂NH₃)[(VO)(SeO₃)₂] has a layered structure composed of alternating VO₅ and SeO₃ units with protonated ethylenediamine as interlayer guest.     

Synthesis, characterization and performance of vanadium hexacyanoferrate as electrocatalyst of H2O2

The present work reports for the first time on the synthesis, characterization and performance of vanadium hexacyanoferrate (VHCF) as electrocatalyst of hydrogen peroxide. VHCF was synthesized by mixing V₂O₅ · nH₂O xerogel with ascorbic acid and K₄[Fe(CN)₆] in double distilled water. X-ray powder diffraction, energy dispersive spectroscopy, scanning electron microscopy, and IR-spectroscopy data suggest the formation of nanocrystalline (mean crystal size 11 nm) compound with a tentative molecular formula K₂(VO)₃[Fe(CN)₆]₂. Composite films of VHCF with poly(vinyl alcohol) were developed over a glassy carbon electrode, and then covered with different (neutral, positively or negatively charged) membranes. The effect of each membrane on the working stability of the resultant sensors was evaluated. Cyclic voltammetry experiments showed that composite films exhibit a pair of reversible redox peaks, and a remarkable low potential electrocatalysis on both the reduction and oxidation of hydrogen peroxide. A linear calibration curve over the concentration range 0.01–3.0 mM H₂O₂ was constructed. Limit of detection (S/N = 3) of 4 μM H₂O₂ was calculated. The proposed transducer is quite selective to hydrogen peroxide. No response was observed in the presence of 10 mM ascorbic acid.     

A novel organically templated three-dimensional open framework vanadium tellurite: (NH3CH2CH2NH3)2V2Te6O18

A novel organically templated vanadium tellurite (NH₃CH₂CH₂NH₃)₂V₂Te₆O₁₈ (1) has been hydrothermally synthesized and characterized by elemental analyses, IR, thermal stability analysis, magnetic susceptibilities and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P2₁/n, , , , β=94.789(4)°, , Z=2, R₁[I>2σ(I)]=0.0187, wR₂[I>2σ(I)]=0.0482. Compound 1 exhibits a novel three-dimensional (3D) vanadium tellurite anion framework composed of vanadium, tellurium, and oxygen atoms through covalent bonds, with the [NH₃CH₂CH₂NH₃]²⁺ cations residing in the channels.     

Structure and infrared emissivity of silicon-containing polyimide/BaTiO3 nanocomposite films

Silicon-containing polyimide/BaTiO₃ nanocomposite films were prepared by the direct mixing of silicon-containing polyamic acid and BaTiO₃ nanoparticles under ultrasonic wave irradiation, followed with thermal imidization. Structure and thermal properties were measured with FTIR, XPS, SEM, DSC and TGA. The results showed that the compatibility of BaTiO₃ and a polyimide might be improved by the introduction of dimethylsilylene groups into the backbone of a polyimide; and BaTiO₃ nanoparticles in the nanocomposites tended to form clusters. The clusters coalesced into a more uniform structure at a higher BaTiO₃ filling than at a lower one.The interfacial interaction between BaTiO₃ and the silicon-containing polyimide resulted in the increase of the glass transition and the thermal decomposition temperature. It was found that the nanocomposites exhibited lower infrared emissivity value than the pure polyimide and the magnitude of infrared emissivity value was related to the content of BaTiO₃ in the nanocomposites.     

Synthesis and structural characterization of (H4APPIP)[V3(C2O4)2(HPO4)3(PO4)(H2O)]·6H2O (APPIP=1,4-bis(3-aminopropyl)piperazine), a layered vanadium oxalatophosphate containing double 6-ring units

A new vanadium(III) oxalatophosphate has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction and thermogravimetric analysis. It crystallizes in the triclinic space group with a=11.604(2) Å, b=12.391(2) Å, c=15.220(3) Å, α=71.090(3)°, β=82.630(3)°, γ=62.979(3)°, V=1843.8(5) Å³ and Z=2. The structure consists of V₆(HPO₄)₆ double 6-ring (D6R) units connected by coordinating C₂O₄²⁻ and PO₄³⁻ anions to form anionic sheets in the ab plane with charge-compensating quadruply protonated 1,4-bis(3-aminopropyl)piperazinium cations and water molecules between the sheets. It is one of the few compounds with 2D layer structures and the second example containing D6R units in the system of metal oxalatophosphates. The iron analogue was also synthesized.     

Monitoring of the smoking process by multicommutation Fourier transform infrared spectroscopy

Nicotine was selected as the target molecule for monitoring of the smoking process by multicommutation Fourier Transform Infrared spectroscopy (FTIR). The method involved the use of CHCl₃ for on-line extraction of nicotine from tobacco, cigarette filters and tobacco ash from NH₄OH alkalinized samples, and absorbance measurement of the characteristic band at 1316 cm⁻¹ in the stopped-flow mode, by obtaining the peak area in the range between 1334 and 1300 cm⁻¹. Under the best operational conditions, the procedure developed provided a detection limit of 0.05 mg mL⁻¹ nicotine, corresponding to 0.5 mg g⁻¹ in the solid sample, a relative standard deviation less than 2.5%, and a sampling frequency of 12 determinations h⁻¹. It can be concluded that nicotine migrates in the smoke mainstream towards the filter during the smoking process. The smoking of cigarettes and cigars is different. Nicotine is retained weakly by both tobacco and filter in the case of cigarettes, and strongly by the unburned tobacco in cigars. The incomplete smoking of cigars and cigarettes reduces nicotine intake and thus reduces the additive effect.     

A simple method for predicting the frequency of the infrared inactive carbonyl stretching mode in LM(CO)5 molecules with C4V symmetry

The paper presents a new method for predicting the frequency of the b₁ mode, which is infrared-inactive, in complexes of the type LM(CO)₅ belonging to C_4V point group. The method was based on the relation λ₃=λ₄+[(1−δ/δ)](λ₁−λ₂), where δ=(λ₁−λ₂)/(λ₁−λ₂+λ₃−λ₄), λ₁, λ₂, λ₃ and λ₄ are the λ parameters of the , , b₁ and e modes, respectively. For a large numbers of complexes of the type LM(CO)₅ the average value of δ was found to be 0.80, with a standard deviation of 0.02. With the use of average value of δ, the frequencies of b₁ mode were estimated. The result obtained indicated that there exists a rather good fit between observed and calculated frequencies, with a mean error of 2.7 cm⁻¹. In addition, it was shown that the δ parameter can be used as a criterion of the correct band assignment for the complexes understudy.     

Protonated MF3 (M = N-Bi): Structure, stability, and thermochemistry of the H-MF3 and HF-MF2 isomers

The structure, stability, and thermochemistry of the H(MF₃)⁺ isomers (M = N-Bi) have been investigated by MP2 and coupled cluster calculations. All the HF-MF₂⁺ revealed weakly bound ion-dipole complexes between MF₂⁺ and HF. For M = N, As, Sb, and Bi they are more stable than the H-MF₃⁺ covalent structures (free energy differences) by 6.3, 14.3, 32.1, and 73.5 kcal mol⁻¹, respectively. H-PF₃⁺ is instead more stable than HF-PF₂⁺ by 21.8 kcal mol⁻¹. The proton affinities (PAs) of MF₃ at the M atom range from 91.9 kcal mol⁻¹ (M = Bi) to 156.5 kcal mol⁻¹ (M = P), and follow the irregular periodic trend BiF₃ < SbF₃ < AsF₃ < NF₃ < PF₃. The PAs at the F atom range instead from 131.9 kcal mol⁻¹ (M = P) to 164.9 kcal mol⁻¹ (M = Bi), and increase in the more regular order PF₃ ≈ NF₃ < AsF₃ < SbF₃ < BiF₃. This trend parallels the fluoride-ion affinities of the MF₂⁺ cations. For protonated NF₃ and PF₃, the calculations are in good agreement with the available experimental results. As for protonated AsF₃, they support the formation of HF-AsF₂⁺ rather than the previously proposed H-AsF₃⁺. The calculations indicate also that the still elusive H(SbF₃)⁺ and H(BiF₃)⁺ should be viable species in the gas phase, exothermically obtainable by various protonating agents.     

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.