Intercalation behaviour of organic derivatives of α-zirconium phosphate

The intercalation behaviour of some organic derivatives of -zirconium phosphate was investigated. Prepared organic derivatives of -zirconium phosphate can be described by the general formula Zr(RPO₃)_X(R'PO₃)_2–X. It was found that only the compound with acidic P–OH groups is able to intercalate different species while the benzene derivatives with phosphite groups do not show any intercalation properties.     

Intercalation of N, N-dimethyl-1-phenylethylamine into α-Zirconium Phosphate

The intercalation and deintercalation of N, N-dimethyl-1-phenylethylamine (N,N-amine) into -zirconium phosphate was investigated by pH titration. N,N-amine was taken up easily in one step to give a new phaseZr(HPO⁴)(HPO₄·N,N-amine) · H₂O, which was characterized by X-ray diffractometry, IR spectroscopy, and thermal analysis. Therelease of N,N-amine from the solid was found to be irreversible due to structural changes in both the intercalation and deintercalation reactions.     

Intercalates of α-Sn(HP04)2·H2O with aromatic and heterocyclic bases and some comments on their orientation in the interlayer region

The intercalation of amines into -tin(IV) hydrogen phosphate, -Sn(HP0₄)₂·H₂0, (-SnP) can occur to give mono- or bilayers of the guest molecule. The distribution and orientation of the amines is influenced by geometrical factors, acidity of the guest molecule and moreover, the degree of charge localisation of the guest organic cations. Regarding the monolayer formation, there are two possibilities. The first is that aromatic amines form monolayers with parallel orientation of the amine with respect to the phosphate layer, when the charge is delocalised over the aromatic ring. Monolayer formation with perpendicular orientation occurs when the positive charge is localised in opposite parts of the aromatic ring molecule. Bilayer formation occurs when the positive charge is localised in one part of the molecule and simultaneous interaction with two adjacent layers is not possible.     

The Intercalation of 4-Aminopyridine into Layered FePS 3

A new intercalation compound,Fe_0.81PS₃(4-aminopyridineH)_0.38, issynthesized by the direct reaction of4-aminopyridine with layered FePS₃ inthe presence of acetic acid.From the XRD results it was found that there aretwo phases (Phase I and Phase II)in this intercalation compound and that4-aminopyridines as the guests adopt twodifferent orientations between theinterlayer region of the host (FePS₃).In one of them with the latticeexpansion (d) of 6.0 Å thering plane of the guest is perpendicular to thelayer and in the other with d of3.4 Å the ring plane of the guest is parallel tothe layer of the host. The IR spectraimply that the inserted guests take theprotonated form to maintain the charge balanceof the intercalation compound.Magnetic measurements indicate thatFe_0.81PS₃(4-aminopyridineH)_0.38 exhibitsparamagnetism in the range of measurementtemperature (1.8 : 300 K),where the magnetic behavior is wellin agreement with the Curie-Weiss Lawabove 55 K.     

Thermal characterisation of chemically reduced electrolytic manganese dioxide

Summary Samples of electrolytic manganese dioxide (EMD) were chemically reduced using 2-propanol under reflux (82°C) for 1, 2, 3, 6 and 24 h intervals. XRD analysis showed that the -MnO₂ structure was preserved although the lattice dimensions were observed to increase with increasing degree of reduction to accommodate the intercalation of protons. The exception was the 24 h reduced sample which contained two phases; -MnO₂ and -MnOOH. Three regions of decomposition in the range of 50 to 1000°C were observed using thermogravimetric analysis coupled with mass spectrometry (TG-MS) and were accounted for as water removal below 390°C, reduction of MnO₂ to Mn₂O₃ between 400 and 600°C, and Mn₂O₃ to Mn₃O₄ between 600 and 1000°C. Again the exception proved to be the 24 h reduced sample which was observed to decompose predominantly in one step between 400 and 600°C directly to Mn₃O₄.     

Thermodynamics of Lithium Intercalates in Carbonized Fabric

The method of quasi-equilibrium galvanostatic curves was applied to study the thermodynamics of lithium deintercalation from the system Li _x C₆ (solid phase)/Li⁺ (solution) in the interval 293-323 K and the thermodynamic characteristics (G, S, H) of lithium intercalation compounds in a carbonized fabric in relation to the degree of intercalation x.     

Theoretical investigation of the electronic structure of graphite + LiNH2 intercalation compounds by the MNDO method

The electronic structures of the clusters C₄₈H₂₄, C₄₈H₂₄Li, and C₄₈H₂₄LiNH₂, which are models of intercalation compounds of graphite, have been calculated by a semiempirical quantum-chemical method in the cluster approximation. It has been shown that an Li atom is strongly polarized in a graphite lattice. When a molecule of LiNH₂ is inserted into a graphite matrix, the charge states of the intercalant molecule and the surrounding carbon atoms change. The cause of the strong increase in the inter planar distances in the intercalation compound of LiNH₂ is the antibonding interaction of the MO's of graphite and the intercalant.Institute of Chemistry, Academy of Sciences of the USSR, Far-Eastern Branch. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 2, pp. 12–16, March–April, 1991.     

Intercalation of diamines into zirconium phosphate-phosphite: A layered compound with asymmetric layers

Many primary diamines H₂N(CH₂)_nNH₂ (all the members withn ranging from 0 to 12 with the exception ofn =I 1) have been intercalated within the phosphate regions of layered zirconium phosphate-phosphite. As a general rule, intercalation occurs in two steps that are not well differentiated. The first one leads to intercalation compounds in which the diamines are arranged with their alkyl chain oriented parallel to the layers; the second one to the fully intercalated compounds. These latter compounds have composition Zr(HPO₄)_0.7(HPO₃)1,3-yNH₂(CHn2)·NH₂, withy ranging from 0.36 to 0.49 depending on the nature of the diamine. Not all the diamine molecules are thus diprotonated and they show a tendency to reach a y value of 0.5, corresponding to the total occupancy of the crystal sites available for intercalation. Diamines are arranged as a monolayer of extended molecules and an evident even-odd alternation of the interplanar spacing has been observed.A comparison with the intercalation of-zirconium phosphate for the same diamines is also made.     

Intercalation of Cyclic Amines into α-Titanium Phosphate

The intercalation of some amines (aniline, benzylamine, cyclohexylamine,piperidine, pyridine, pyrazine and piperazine) into -titaniumphosphate, Ti(HPO₄)_2×H₂O,has been investigated by the batch method and/or by exposing the host to thevapour of the amines. The changes in the interlayer distance of the solidduring the intercalation process was followed by X-ray powder diffraction.The new intercalates were characterised by chemical and thermal analysis.Materials with a monolaminar and/or bilaminar arrangement of amine moleculesin the phosphate interlayer region are obtained depending on the nature ofthe amine. Due to steric hindrance, saturated phases are not obtained forall amines studied. The thermal decomposition of the intercalates (nitrogenatmosphere), takes place in three stages: dehydration, removal of amines andcondensation of the hydrogenphosphate to pyrophosphate groups.     

<Emphasis Type="Italic">In-situ</Emphasis> TEM investigation of MoS<Subscript>2</Subscript> upon alkali metal intercalation

Phase transition in two dimensional molybdenum disulfide (MoS₂) can be induced by several methods and has been investigated for decades. Alkali metal insertion of MoS₂ had been proved an effective method to cause phase transition early in 1970s, and has been gaining renewed interest recently, due to the possible application of MoS₂ in energy storage. The alkali metal intercalation of MoS₂ has been studied by various techniques, among which in-situ transmission electron microscopy (TEM) provides unique capability of real time resolving the structural evolution of the materials at high spatial resolutions. Here by in-situ TEM technique we investigated the structural evolution of MoS₂ upon lithium and sodium intercalation, along with transformation of the nanosheet and variation of the electron diffraction patterns. The intercalation process is accompanied by emergence of superstructures, which exist in several forms. The ion intercalation results in phase transition of MoS₂ from 2H to 1T, and the driving mechanism of the phase transition are discussed. The work provides a more comprehensive understanding of ion intercalation induced phase transition of MoS₂.     

Structural study and crystal chemistry of the first stage calcium graphite intercalation compound

A novel and efficient synthesis method concerning the preparation of the first stage calcium graphite intercalation compound is provided. It makes use of a reaction between liquid metallic alloy and pyrolytic graphite. From now on it is especially easy to obtain bulk CaC₆ samples. Thanks to such samples, it was possible to study in detail the crystal structure of this binary intercalation compound. It has been entirely specified, so that we know that CaC₆ crystal is rhombohedral and belongs to the space group with the following parameters: and α=49.55°. The elemental unit cell contains one calcium atom and six carbon atoms. In this paper, we show also how the various MC₆ structures evolve according to the size of the intercalated element and to the bond nature that appears in the final compound. CaC₆ is unique, since all the other MC₆ compounds exhibit a hexagonal symmetry.     

First and second thermodynamic mixing properties of ethylbenzene +n-alkanes: Experimental and theory

Isobaric expansibilities _P and isothermal compressibilities _T have been determined at 25 and 45°C for binary mixtures of ethylbenzene + n-tetradecane and + n-hexadecane and the corresponding excess functions (V ^E /T)_P and (V ^E /P)_T have also been obtained. With these data and supplementary literature values, the following second order mixing properties are also reported at 25°C: _S ^E , (V ^E /P)_T, C_V and (VT). All mixing quantities have been compared with the results obtained at 25°C by using the Prigogine-Flory-Patterson theory of liquid mixtures. The predicted values suggest that the ability of ethylbenzene as a breaker of the pure n-C_n orientations is similar to what we found for toluene and higher than for p-xylene.     

Oxygen isotope exchange in oxygen-bearing compounds of uranium

Isotope exchange is reported for gaseous oxygen in contact with the following uranium compounds: -Na₂UO₄, -Na₂UO₄, Na₂U₂O₇, UO₃(A), -UO₃, -UO_2.94 and U₃O₈.; qualitative tests have also been done with UO₂F₂ and Cs₂UO₂Cl₄. The times of half-exchange have been determined as functions of temperature for U₃O₈, -UO_2.94, Na₂U₂O₇ and -Na₂UO₄; diffusion coefficients for oxygen have been calculated for UO₃(A), -UO₃, Na₂U₂O₇, -Na₂UO₄ and -Na₂UO₄. Activation energies have been deduced for diffusion and surface exchange. All the oxygen atoms in these compounds are equivalent as regards isotope exchange; the above activation energies increase with the UO ratio in some cases. Diffusion-limited exchange tends to show periodic oscillations in rate not ascribable to errors of measurement; a mechanism is proposed for this.     

Microwave Spectrum and Hindered Pseudorotation of Tetrahydrofuran

The microwave spectrum of the tetrahydrofuran (C₄H₈O) molecule in the ground state and eight excited states of hindered pseudorotation has been studied. A strong perturbation of rotational spectra has been found for three pairs of pseudorotational states, which is due to the vibrational-rotational interaction. To analyze the nonrigid spectra of these states we used the double resonance technique. Two hundred and sixty nine rotational and vibrational-rotational transitions corresponding to the _a and _c components of the dipole moment have been identified. The rotational constants have been determined along with the quartic constants of centrifugal distortion and the spectroscopic parameters of the interaction between the overall rotation and hindered pseudorotation. The splittings of three pairs of quasidegenerate vibrational levels have been calculated: ₀₁ = 21,308.17 MHz, ₂₃ = 61,205.28 MHz, ₅₆ = 68,183 MHz. The potential function of hindered pseudorotation V()=- 7.84(1-cos2)/2+36.10(1-cos4)/2 (cm^–1) was found from the splittings. It is concluded that the molecule has a twisted conformation (C₂ symmetry) in the states =0 and =1 of hindered pseudorotation and a bent conformation (C_s symmetry) in the states = 2 and = 3. The component of the dipole moment of the transition ‹ = 2 |_c | = 3› = 0.57± 0.01D was determined from the Stark effect of the rotational transitions in the = 2, = 3 states.     

Reactivity of 17- and 19-electron organometallic complexes. Formation of bent sandwich 19-electron radical cation complexes of ruthenium and osmium

The redox behavior of sandwich indenyl complexes of the general formula (⁵-C₉H₇)ML (M=Ru and L=⁵-C₉H₇ (1), ⁵-C₅H₅ (2), ⁵-C₅Me₅ (3); M=Os, L=⁵-C₉H₇ (4)) has been studied in THF, MeCN, and CH₂Cl₂ by cyclic voltammetry and controlled potential electrolysis on a Pt electrode in the –85 to +20 °C temperature range. The title complexes have been found to undergo reversible one-electron oxidation to the corresponding radical cations, whose stabilities and reactivities depend on the nature of both the metal and °-ligands and of the nucleophilic properties of the solvent. The fast interaction of the electrogenerated 17-electron radical cations with nucleophiles yields bent sandwich 19-electron radical cations, [(⁵-C₉H₇)M(L)(Nu)]⁺ (Nu = Cl^–, MeCN, or THF), the latter undergoing one-electron oxidation to the corresponding [(⁵-C₉H₇)M(L)(Nu)]²⁺ dications. In the case of Nu=THF, the reaction of the electrogenerated 17-electron radical cations with nucleophiles appears to be reversible. Radical cations [(⁵-C₉H₇)₂M]^+· (M=Ru, Os) have been characterized by ESR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2394–2399, December, 1995.     

Electronic structure of monosubstituted benzenes and X-ray emission spectroscopy

The electronic structure of the benzaldehyde molecule has been studied by X-ray emission spectroscopy. The gas-phase O-K- and C-K-spectra of this compound have been obtained. MNDO quantum-chemical calculations have been carried out. The structure of the MO's of benzaldehyde has been compared with those of benzene and formaldehyde molecules. The character of the p-p interaction of the phenyl and formyl fragments has been considered. The contribution of the latter to the highest occupied molecular orbitals of the-system has been shown to be small.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1033–1037, June, 1994.     

Quantum-chemical calculations of the electronic structure and reactivity of silylenes

The origin of the different reactivities of carbenes and silylenes has been discussed. Molecular orbital calculations have been carried out in order to estimate the effects of substituents on the singlet-triplet splittings E _ST in these molecules. The data ofab initio calculations have been used to establish the linear correlation between E _ST values for carbenes and silylenes. Both qualitative and quantitative appraisals of the applicability of the semiempirical MNDO method to calculations of E _ST values for carbenes and silylenes have been derived. E _ST values for a large number of substituted carbenes and silylenes have been computed by the PM3 method, one of the latest versions of the MNDO approach (Ref. 14).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1006–1008, June, 1994.     

Reactions of the radical cations of aliphatic aldehydes in freon matrices

ESR spectra of -irradiated, at –196 °C, solutions of acetic and propionic aldehydes in freon-11 and freon-113 affected by aldehyde concentration, temperature, and the action of light have been studied. It has been shown that the radical cations CH₃CHO⁺ are converted into neutral radicals CH₃O and CH₃HOH and the cations CH₃CH₂CHO⁺. are converted to RO and CH₃HCHO due to ion-molecular reactions of proton transfer /CH₃O and CH₃HCHO/ of hydrogen atom transfer /CH₃HOH/.     

Apparent molal volumes and heat capacities of some 1:1 electrolytes in anhydrous methanol at 25°C

A flow calorimeter and flow densimeter have been used to measure volume specific heats and densities of solutions of LiCl, LiBr, NaCl, NaBr, KF, KBr, Kl, CsF, and Bu₄NBr in anhydrous methanol at 25°C. The concentrations ranged from approximately 0.01m to close to saturation in some cases. Apparent molal heat capacities _cp and volumes _v have been evaluated and extrapolated to infinite dilution to obtain _cp ^o and _v ^o . Nearly all the heat capacities in methanol are negative. However, with the exception of the lithium halides and Bu₄NBr they are more positive than heat capacities of the corresponding salts in water. The dependence of the heat capacities on ionic radii is generally opposite in methanol solutions from that observed for aqueous solutions. In agreement with others, the _v ^o data indicate that electrostriction in methanol solutions is greater than in aqueous solutions.     

Crystal and molecular structure of the guaianolide gaillardin

The epigeal part ofPulicaria uliginosa (P. dysenterica) has been investigated for the first time for its -lactone content. The guaiane -lactone gaillardin, C₁₇H₂₂O₅ has been isolated, and its crystal and molecular structures have been established by the x-ray structural method (diffractometer, CuK, 770 reflections, direct method, R = 0.108).