IR study of ion-molecular interactions in the system methanesulfonic acid-ethyl acetate

The complex formation in the methanesulfonic acid (MSA)—ethyl acetate (EA) system was studied by Multiple Attenuated Total Reflection (MATR) IR spectroscopy at 30°C. In solutions with excess EA, neither protonation of a base nor formation of complexes with a strong symmetrical H bond was observed. Molecular complexes EA·MSA are found in these solutions. Complexes formed by the strong symmetric H bond are observed in the system when the MSA content exceeds 50 mol.% Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2. pp. 292–294, February, 2000.     

IR spectroscopic study of ion-molecular interactions in the methanesulfonic acid—N,N-dimethylformamide system

Complex formation in the methanesulfonic acid (MSA)-DMF system was studied by Multiple Attenuated Total Reflectance (MATR) IR spectroscopy at 30°C within the composition range from neat MSA up to neat DMF. Depending on the ratio of components, two types of complexes with a strong quasi-symmetrical H bond (1 and2) are formed. The uncharged complex1 is a quasi-ion pair with the (O…H…O) bridge. Complex2 is formed by a protonated DMF molecule and the (A…H…A)⁻ anion bound as an ion pair. It is established that complexes1 are solvated by DMF molecules in an excess of a base. Solvation or2 in an excess of an acid corresponds to a change from contact to contact-separated ion pairs. Continuous absorption spectra of charged and uncharged complexes1 and2 were obtained. The schemes of acid-base interactions in the MSA-DMF and HCl-DMF systems were compared. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2484–2489, December, 1998.     

Synthesis,crystal structure and other properties of the complexes of Er(III), Yb(III) and Lu(III) with 4,4′-bipyridine and dichloroacetates

A novel mixed-ligand complexes of Er(III), Yb(III) and Lu(III) with title ligands were prepared and characterized by chemical and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulphoxide). The thermal properties of complexes in the solid state were studied. The mode of metal–ligand coordination was discussed. The title compounds are isomorphic and isostructural in solid state. All atoms in studied compounds lie in general positions but occurrence of inversion on the midpoint of the bond linking two pyridine rings leads to existence in asymmetric unit one complex molecule and half of outer coordination sphere 4-bpy molecule. All chelating carboxylate groups are symmetrically bonded to the metal cations. The molecules of studied compounds are connected to the three dimensional network via O–H···O and O–H···N intermolecular hydrogen bonds. In the structures also exist C–H···O, C–H···Cl weak hydrogen bonds and π····π stacking interactions.     

Intramolecular S···O chalcogen bond in thioindirubin

Results of X-ray diffraction study and quantum-chemical calculations revealed that molecular conformation of thioindirubin molecule creates suitable conditions for formation of intramolecular C–H···O and S···O interactions. Analysis of molecular electrostatic potential (MEP) demonstrates existence of two areas of positive MEP (σ-holes) in the outermost part of the sulfur atom on the continuation of the lines of the C–S bonds. One of these σ-holes is oriented toward region of negative MEP around the oxygen atom of carbonyl group. Such situation corresponds to formation of σ-hole or chalcogen bond. Existence of both types of bonding interactions is confirmed by topological analysis of electron density distribution using “Atoms in Molecules” (AIM) theory. Energies of the C–H···O hydrogen bond and the S···O σ-hole bond derived from AIM and NBO theories are very close.     

Intermolecular interactions in orthophosphoric acid-<Emphasis Type="Italic">N,N</Emphasis>-dimethylformamide system according to viscometric data

The viscosity of an orthophosphoric acid—N,N-dimethylformamide system was measured in the whole region of compositions at 298–338 K. An excess viscosity of the system was analyzed by the data obtained using different model concepts. Calculations suggested that strong intermolecular interactions and the formation of complexes (H₃PO₄)₂·DMF occur in the system. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2252–2256, October, 2005.     

Complexes with strong symmetric hydrogen bonds and their solvation in the trifluoroacetic acid—N,N-dimethylformamide system studied by IR spectroscopy

Complex formation in the trifluoroacetic acid (TFA)—DMF system containing TFA from 0 to 100 mol.% was studied by IR multiple attenuated total reflectance (MATR) spectroscopy at 30°C. The formation of uncharged 1∶1 TFA—DMF complexes with a quasi-ion structure and partial proton transfer to the O atom of the DMF molecule (quasi-ion pairs) were observed in the TFA—DMF system with the TFA content from 0 to 90 mol%. Depending on the ratio of the components, the quasi-ion pairs are solvated by the DMF or TFA molecules. The solvation of the quasi-ion pairs slightly changes the parameters of the central strong H bond. When the acid concentration reaches 80 mol.%, the proton adds to the DMF molecule to form the ion pair (DMF)H⁺·(A...H...A)⁻, whose anion contains a strong symmetric H bond.     

EPR spectra and structures of dinuclear copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with acyldihydrazones of benzenedicarboxylic acids

Spacer-armed dinuclear copper(II) complexes with condensation products of isophthalic and terephthalic acid dihydrazides with salicylaldehyde and 2-hydroxyacetophenone were synthesized and studied by EPR and X-ray diffraction. The compositions and structures of most of the complexes were determined by elemental analysis, thermogravimetric analysis, and IR spectroscopy. The structure of the copper(II) complex with acyldihydrazone of salicylaldehyde and 1,3-benzenedicarboxylic acid (H₄L) with the composition [Cu₂L¹·2morph·MeOH] (morph is morpholine) was established by X-ray diffraction. The Cu^II atoms are spaced by 10.29 Å and are structurally nonequivalent. One copper cation has a square-planar coordination formed by donor atoms (2 N + O) of the doubly deprotonated acylhydrazine fragment and the N atom of the morpholine molecule. The second copper atom is additionally coordinated by a methanol molecule through the oxygen atom, so that this copper atom is in a tetragonal-pyramidal coordination with the oxygen atom in the axial position. The EPR spectra of liquid solutions of the complexes based on 1,4-benzenedicarboxylic acid acyldihydrazones and 1,3-benzenedicarboxylic acid bis(salicylidene)hydrazone at room temperature show a four-line hyperfine structure with the constant a _Cu = 54.4–67.0·10⁻⁴ cm⁻¹ (g = 2.105–2.147), which is indicative of the independent behavior of the paramagnetic centers. The EPR spectrum of a solution of the complex based on isophthalic acid and 2-hydroxyacetophenone shows the seven-line hyperfine structure corresponding to two equivalent copper nuclei (g = 2.11, a _Cu = 36.5·10⁻⁴ cm⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1898–1905, October, 2007.     

Features of the oxidative polymerization of aminothiazole in the presence of iron(III) chloride

A new conjugated polymer with semiconducting characteristics-polyaminothiazole-was obtained by oxidative polymerization of 2-aminothiazole in the presence of iron(III) chloride. A reaction scheme is proposed on the basis of the data from IR, ESR, and electronic spectroscopy. It involves the formation of an intermediate aminothiazole-FeCl₃ complex with coordination of the initiator at the nitrogen atom and subsequent oxidation of another molecule of aminothiazole by this complex with the formation of a radical-cation, leading to polymerization. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 2, pp. 91–95, March–April, 2007.     

Volume properties of solutions of oleic, linoleic, and linolenic acids in n-hexane and n-heptane at 298.15 K

Densities of solutions of oleic, linoleic, and linolenic acids in n-hexane and n-heptane were measured using a vibrating-tube densimeter at 298.15 K in a concentration range of 0–0.012 molar fractions of solute. The measurement error does not exceed ±5·10⁻⁶ g cm⁻³. The limiting partial molar volumes of fatty acids of the studied series in n-hexane and n-heptane and the excess volume properties of binary mixtures were calculated. On going from oleic to linolenic acid, the number of double bonds (>C=C<) in a solute molecule increases, the hydrocarbon chain length in a solvent molecule decreases, and compactness of the structure packing of the resulting solution increases. This is caused, as a whole, by the enhancement of the n-alkane—acid intermolecular interaction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 643–647, April, 2006.     

Secondary reactions of ethylene and propylene in the Fischer-Tropsch synthesis on cobalt-aluminum and cobalt-chromium catalysts

The only secondary reaction of olefins in the Fischer-Tropsch synthesis on Co/SiO₂·Al(III) and Co/SiO₂·Cr(III) with 2.7·10⁻⁶ and 4.0·10⁻⁶ g-ion/m² cation concentration in the support matrix, respectively, is dimerization of ethylene to give a four-carbon intermediate, which participates in the growth of C-C bond chains according to the classical FT synthesis mechanism. When the chromium concentration is increased by a factor of 1.7, secondary ethylene reactions occurring on the acid sites of the catalyst are also observed. When the aluminum concentration is increased by a factor of 3.4, we observe the oligomerization of ethylene and propylene. The secondary reactions of ethylene mainly result in linear hydrocarbons, while oligomerization involving propylene gives a significant amount of branched hydrocarbons. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 2, pp. 115–120, March–April, 2008.     

新型成膜电解液添加剂亚硫酸丁烯酯的电化学行为

合成制备了一种新的环状亚硫酸酯类有机溶剂——亚硫酸丁烯酯(BS). 量子化学计算结果表明, 亚硫酸丁烯酯有机溶剂分子的总能、LUMO值比碳酸丙烯酯有机溶剂的低, 具有较强的得电子能力, 不易被氧化. 其作为添加剂与碳酸丙烯酯(PC)混合应用于锂离子电池中, 可有效地抑制PC在石墨电极中的共插入, 能显著改善循环性能.     

Acidity function of methanesulfonic acid solutions in DMF

The acidity function of solutions of methanesulfonic acids (MSA) in DMF and H₂O were measured by the indicator method at 25 °C in the 0–100% concentration range. A higher ionizing activity of HCl complexes with DMF as compared to that of similar MSA complexes was established. The relative ionizing activity of MSA molecules, H₅O₂ ⁺ ions, and ion pairs between MSA and DMF was determined. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 1940–1943, October, 1999.     

Conduction of Li+ cations in ethylene carbonate (EC) and propylene carbonate (PC): comparative studies using density functional theory

Density functional theory is used to study the interaction of Li⁺ cation with ethylene carbonate (EC) and propylene carbonate (PC) comparatively, which are the most popular solvents used in lithium-ion battery composite. In our theoretical calculations, we use DFT hybrid parameter B3LYP5 with a basis set 6–31G** by means of PCGAMESS/Firefly software package. We analyze the optimized structures of EC, PC, and their clusters including lithium-ion. We then calculate solvation energy, desolvation energy, electron affinity, Gibbs free energy, heats of formation of Li⁺ solvated by EC and PC, and the charge on Li⁺. From the above analysis, we observe EC as a better solvent than PC in applications of lithium-ion batteries.     

Synthesis, spectral and thermal properties, and crystal structure of catena-poly-μ-ethylenediamine(dipicolinato)zinc(II) trihydrate, {[Zn(dipic)(μ-en)]·3H2O}n

A novel metal–organic coordination polymer framework formulated as {[Zn(dipic)(μ-en)]·3H₂O} _n (1) (catena-poly-μ-ethylenediamine(dipicolinato)zinc(II) trihydrate) has been synthesized and characterized by spectral method (IR), elemental analysis, thermal analysis (TG, DTG, DTA) and single crystal X-ray diffraction techniques. It crystallizes in the triclinic system, space group P−1. The asymmetric unit contains three hydrogen-bonded water molecules and the Zn atom is five-coordinated by three N and two O atoms. In fact, it is a new one-dimensional zinc complex with the peculiarity of having the ethylenediamine ligand very unusually acting as bridge to form polymeric chains. In the crystal structure, intramolecular O–H···O and intermolecular O–H···O and N–H···O hydrogen bonds result in the formation of a supramolecular structure, in which they seem to be effective in the stabilization of the structure.     

X-ray crystal structures of halogen containing nucleobase derivatives in unsolvated and DMSO solvated forms

A series of halogenated nucleobase derivatives 1–4 is reported to yield solvent-free (2) and DMSO solvated crystals (1, 3, 4) on the crystallization from DMSO with one of them (4) containing an additional molecule of water. The molecular and crystal structures are described and comparatively discussed with reference to previous results on related compounds. The molecule of 1 is planar, molecules of 2 and 3 show syn alignment with reference to the heterocyclic ring and common C2′-endo conformation of the ribose residue, while 4 is also syn aligned but C4′-exo in the sugar conformation. The packing structures reveal typical aggregations created via networks of hydrogen bonds. These involve conventional N–H···N, N–H···O and O–H···O interactions between nucleobase and ribose units as well as solvent molecules, additionally supported by weak C–H···O contacts but excluding the participation of halogen···halogen interactions as well as halogen···heteroatom contacts in the supramolecular structure formation.     

Mechanism of the catalytic action of the mechanoactivated salt K2PTCL4 in the gas-phase hydrochlorination of acetylene

A heterogeneous catalyst for the hydrochlorination of acetylene by gaseous HCl is formed as a result of mechanical treatment of the solid salt K₂PtCl₄ in an atmosphere of acetylene, ethylene, or propylene by the formation of π complexes of platinum(II) as active centers in the surface layer under these conditions. The controlling stage of the catalytic reaction is chloroplatination of the π-coordinated acetylene by the HCl molecule. The reaction takes place as a concerted process, in which an intermediate β-chlorovinyl derivative of platinum(II), a complex of platinum with a coordination vacancy[PtCl ₃ ^* ]⁻, and a new molecule of HCl are formed simultaneously with cleavage of the H—Cl and Pt—Cl bonds in the metal complex adjacent to the π-acetylene complex. The catalytic cycle closes with rapid dissociation of the organoplatinum intermediate by the action of HCl, giving the final product and the initial complex [PtCl₄]²⁻. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 306–311, September–October, 2006.     

Arsenopyrite mineral based electrochemical sensor for acid–base titrations in γ-butyrolactone and propylene carbonate

Abstract  

A novel acid–base sensor based on the natural mineral arsenopyrite for titrations in γ-butyrolactone and propylene carbonate is validated and studied. This sensor, which requires only small sample volumes, was employed for the titrations of some important organic acids (benzoic, anthranilic, and salicylic acid) with potassium hydroxide. A stable stationary potential was attained at the arsenopyrite electrode in γ-butyrolactone and propylene carbonate in less than 5 min. The change in the electrode potential from the acidic to basic region was 379 to −160 mV in γ-butyrolactone and 434 to −67 mV in propylene carbonate. The arsenopyrite electrode showed a relatively fast response time in the investigated solvents (11 s in γ-butyrolactone and 14 s in propylene carbonate). It can be used without any time limit or without considerable divergence in the potential. The investigated electrode showed a linear dynamic response for p-toluenesulfonic acid concentrations in the range 0.1–0.001 M, and a sub-Nernst dependence in γ-butyrolactone as well as in propylene carbonate. Unlike traditional pH titration, an end-point color indicator is unnecessary in this method, and real-time monitoring can be realized. The relative standard deviations for measurements of benzoic, anthranilic, and salicylic acids were 0.10–0.31%, which show that the repeatability and accuracy of measurements taken with the sensor are satisfactory.     

Cationic polymerization of hydrocarbon monomers induced by complexes of acyl halides with Lewis acids

The ionic complex of mesitoyl bromide with aluminum bromide in a 1∶1 composition (Mst-1) does not initiate the isobutylene polymerization inn-hexane or methylene dichloride at −78 °C. The corresponding ionic complex of the 1∶2 composition (Mst-2) acts as a cationogenic initiator of the polymerization. The addition of excess Lewis acid or introduction of organic electron acceptors increases the initiating activity of the Mst-1 complex and activates acyl complexes of the 1∶2 composition including Mst-2. The results are discussed in terms of the effect of specific solvation on the nucleophilicity of counteranions, which makes the addition of the monomer to the carbocation possible. For Part 9, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 52–56, January, 1998.     

Quantum chemical calculations of the molecular structure of diphenylguanidine and experimental studies of its tautomerism in solution

MNDO-PM3 and AM1 quantum chemical calculations of the molecular structure of N,N′-diphenyl-guanidine (DPG) prove that the molecule preferably exists as an asymmetric tautomer with a basic center C = N−. IR and UV spectral data, dipole moments, and average molecular weights of DPG solutions in nonpolar and low-polar solvents confirm the results of calculations, indicating formation of hydrogen-bonded cyclic self-associates of DPG in solution. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 618–625, July–August, 1998.     

The structure and thermal behaviour of sodium and potassium multinuclear compounds with hexamethylenetetramine

Sodium and potassium thiocyanate complex compounds of formulae [Na(hmta)(H₂O)₄]₂²⁺·2SCN⁻ (1) and [K₂(hmta)(SCN)₂] _n (2) have been synthesized and characterised by IR spectroscopy, thermogravimetry coupled with differential thermal analysis, elemental analysis and X-ray crystallography. Each sodium and potassium cation is six co-ordinated, the sodium by one monofunctional hmta molecule, three terminal water molecules and two bridging water molecules, and the potassium by two bridging tetrafunctional hmta molecules and four bridging tetrafunctional thiocyanate ions. The coordination polyhedra of the central atoms can be described as distorted tetragonal bipyramids. The complex cations and anions of (1) are interconnected by multiple intramolecular O(water)—H···N(hmta/NCS) and O(water)—H···S hydrogen bonds to the three dimensional net. In each complex cation the intramolecular O–H···O hydrogen bonds link two terminal water molecules bonded to two metal cations. The compound (2) forms the three dimensional hybrid network in which the classical two-dimensional coordination polymers are linked by inorganic SCN⁻ spacers to the third-dimension. Thermal analyses show that the compounds decompose gradually in three (for 1) and two (for 2) steps with formation of Na₂SO₄ and K₂S as the final products, respectively, for 1 and 2.