Home – Home – Jornals – Journal of Structural Chemistry 2014 number 4

The structures and stability of bi- and trinuclear Al clusters at the cationic sites in an 8-membered ring of mordenite are calculated within the cluster approach using the DFT method. Adsorption heats of hydrogen and water, hydrogenation and hydrolysis reactions are compared with similar values for the Ga cluster at the cationic sites of a similar Ga-exchange form of mordenite whose existence is consistent with the experiment. The effect of a different arrangement of lattice aluminum atoms in the 8-membered ring of mordenite is analyzed.

The adiabatic bound state of an excess electron is calculated for a water cluster (H₂O)₈^- in the gas phase using the DFT-B3LYP method with the extended 6-311++G(3df,3pd) basis set. For the liquid phase the calculation is performed in the polarizable continuum model (PCM) with regard to the solvent effect (water, e = 78.38) in the supermolecule-continuum approximation. The value calculated by DFT-B3LYP for the vertical binding energy (VBE) of an excess electron in the anionic cluster (VBE (H₂O)₈^- = 0.59 eV) agrees well with the experimental value of 0.44 eV obtained from photoelectron spectra in the gas phase. The VBE value of the excess electron calculated by РСМ-B3LYP for the (H₂O)₈^- cluster in the liquid phase (VBE = 1.70 eV) corresponds well to the absorption band maximum λ_max = 715 nm (VBE = 1.73 eV) in the optical spectrum of the hydrated electron e_hydr^-. Estimating the adiabatic binding energy (ABE) e_hydr^- in the (H₂O)₈^- cluster (ABE = 1.63 eV), we obtain good agreement with the experimental free energy of electron hydration ΔG₂₉₈⁰ (e_hydr^-) = 1.61 eV. The local model (H₂O)₈^2- of the hydrated dielectron is considered in the supermolecule-continuum approximation. It is shown that the hydrated electron and dielectron have the same characteristic local structure: -O-H{}H-O- and -O-H{↓}H-O- respectively.

The interaction of the conformational degrees of freedom of azomethines in the nematic phase, which is induced by electronic donor-acceptor properties of the terminal substituents of the benzylideneaniline core is studied. These degrees of freedom related to the rotation angles φ_k around the bonds between the substituent and the aniline ring (φ₁) and also between the CH=N bridge and the aniline ring (φ₂) are characterized by the parameters Q_k = ‹cos²φ_k›. It is found that the interaction of these degrees of freedom is manifested in the linear dependence Q₂( Q₁). Within the phenomenological theory the effect of this interaction on changes δ_k in the Q_k values during the nematic liquid crystal-isotropic liquid phase transition is revealed along with the temperature T_NI and character of this transition. The derivation of previously established empirical dependences T_NI( Q_k ) is presented in the presence of direct and indirect steric effects of side substituents affecting the Q_k values. A diverse combination of δ_k signs in the nematic phase, which is a prerequisite for the conformational polymorphism of the nematic phases of azomethines, is shown.

We present density functional calculations of Al_nAu clusters for n = 1–15. The growth pattern for Al_nAu ( n = 1–7, 12, 14, 15) clusters is the Au atom occupying a peripheral position of Al_n clusters, and the growth pattern for Al_nAu(n = 8, 10 and 13) clusters is Au-substituted Al_n+1 clusters. It is found that the Au atom replaces the surface atom of an Al_n+1 cluster and occupies a peripheral position. In addition, the ground state structures of Al_nAu clusters are more stable than pure Al_n clusters. It is found that the Al₁₃Au cluster exhibits high stability.

A molecular crystal of silver cyclic amide Ag ₂(C ₄H ₄NO ₂) ₂(H ₂O) is studied using first-principles density functional theory calculations within the generalized gradient approximation (GGA). A number of different exchange-correlation functionals are considered for a possible treatment of the system. It is found that the Perdew-Burke-Ernzerhof (PBE) GGA exchange-correlation functionals are adequate for the Ag ₂(C ₄H ₄NO ₂) ₂(H ₂O) crystal. The results obtained show the possibility to reproduce rather well the geometry of at least some molecular crystals by means of the periodic solid-state calculations if the computational parameters are chosen adequately. The present work also reports the analysis of the chemical bonding in the material and gives the total and partial density of states. Our solid-state computations point out the possible magnetic properties of the molecular crystal under study.

The properties of the electronic structure of the Disiline-doped boron nitride nanotubes (Disiline-BNNTs) are investigated by a density functional theory (DFT) calculation. The structural forms are firstly optimized and the CS tensors calculated. Subsequently, the chemical-shielding isotropic (CS ^I) and chemical shielding anisotropic (CS ^A) parameters are found. The shielding values of boron (B) and nitrogen (N) atoms were calculated by Gauge-Including Atomic Orbital (GIAO), Continuous Set of Gauge Transformations (CSGT) and Individual Gauges for Atoms in Molecules (IGAIM) methods, using B3LYP/6-311+G*. The B3LYP level of theory with IGAIM was the best method to evaluate the theoretical chemical shifts for studied models. The results reveal a significant effect of Disiline doping on the chemical shielding tensors at the sites of those ¹¹B and ¹⁵N nuclei located in the nearest neighborhood of the Disiline-doped ring. Furthermore, the values of dipole moments and HOMO-LUMO gaps change in the Disiline-doped models in comparison with the original pristine model.

The energies of intramolecular С-H⋯O, N-H⋯O and О-H⋯O hydrogen bonds in model compounds are empirically estimated based on the values of the hydrogen bond induced weak-field shift of the bridging hydrogen atom signal in the ¹Н NMR spectrum. It is supported by a theoretical estimation of these energies based on the electron density value at the hydrogen bond critical point calculated within the QTAIM method. Good agreement between the empirical and theoretical estimates is found, which gives evidence of their reliability. It is shown that from the standpoint of their strength the intramolecular N-H⋯O and О-H⋯O hydrogen bonds can be classified as moderate whereas the intramolecular С-H⋯O hydrogen bonds must be classified as very weak interactions similar in their energy significance to van der Waals interactions.

The electron spin echo (ESE) method is applied to determine the spin relaxation times of long-term light-induced radicals and short-term spin-correlated radical pairs (SCRPs) formed during pulse laser irradiation of a composite consisting of phenyl-С ₆₁-butyric acid methyl ether (PCBM) and poly-(3-hexylthiophene) (P3HT) at 80 K. Dependences of the ESE signal recorded to measure the longitudinal relaxation times of P3HT ⁺/PCBM ^- SCRPs and the free P3HT ⁺ radical are found to be approximated by the dependence of the form exp(-( t/ T ₁) ^{0 . 6}) with parameters Т ₁ lying in the microsecond range. By means of the instantaneous diffusion model the difference in the transverse spin relaxation times of the P3HT ⁺/PCBM ^- radical pair at complete and incomplete microwave pulse excitation of the echo-detected EPR spectrum is explained. Based on it, the magnetic interaction energy between the electron spins in P3HT ⁺/PCBM ^- SCRPs is estimated; E/ ћ ~ 10 ⁶ s ^-1.

An analysis of the concentration dependences of the molecular light scattering parameters in chlorobenzene- о-chlorotoluene solutions shows that the entire concentration range can be split into three intervals with different structural features: 0-0.2 ppm, 0.2-0.9 ppm, and 0.9-1 ppm chlorobenzene. The features are manifest in physicochemical properties such as sound velocity and excess molar volume, adiabatic compressibility, and molar refraction. Experimental data are compared with those obtained by molecular dynamics simulation. It is concluded that the chlorobenzene structure is determined by Cl…Cl interactions while the structuring of liquid o-chlorotoluene and its solutions is largely determined by intermolecular Cl…Me interactions.

Thermodynamic characteristics are determined for supersaturated (8÷28 m ) aqueous ammonium chloride solutions at 298.15 K: activity as well as partial molar enthalpy, volume, and excess entropy of water, osmotic coefficients, density, and salt hydration numbers. The relative humidity above the solution decreases from 75.6% (8 m solution) to 44.7% (28 m solution). A directly proportional dependence is found between the enthalpy and entropy characteristics. The negative values of the nonideal portion of the Gibbs energy are due to structural effects (excess entropy). The excess entropy of water has the same value 1.8 J/(mol×K) in supersaturated 12 m NaCl and 28 m NH ₄Cl. The ratio 12/28 = 3/7 is also valid for other "isoentropic" molalities of the said salts.

The behavior of natural zeolite-like hetero-framework zirconosilicate hilairite |Na _1.47H _0.53(H ₂O) _2.7| [ZrSi ₃O ₉] is studied by single crystal X-ray diffraction at a high pressure (up to 4.73 GPa): space group R3, a = 10.5667(2) Å, c = 15.9109(4) Å, V = 1538.54(6) Å ³, Z = 6. The compression of hilairite is practically isometric in the whole pressure range studied and is close to linear. Above 3.5 GPa an increasing deterioration of the single crystal is observed, which is interpreted as the started first order phase transition accompanied by significant volumetric changes.

Acid pyridine-3-carboxylic acid dodecatungstenphosphate (С ₆NO ₂H ₅) ₂H[PW ₁₂O ₄₀]×2Н ₂О is synthesized. The compound is studied by chemical analysis, IR spectroscopy, X-ray crystallography, and thermogravimetry. The compound is found to crystallize at 290 K in a hexagonal crystal system (sp. gr. R -3) (I) with the unit cell parameters: а = 33.015(6) Å, с = 12.010(2) Å, g = 120°, V = 11337(4) Å ³, Z = 9. When the temperature decreases to 100 K, a phase transition is observed leading to an increase in symmetry to R -3 m (II), with the unit cell parameters: а = 33.072(1) Å, с = 24.234(1) Å, g = 120°, V = 22955(2) Å ³, Z = 18.

Reaction of K ₂[Ru(NO)Cl ₅] with pyridine in aqueous ethanol at pH ~ 7-8 affords a nitrosoruthenium hydroxocomplex mer -[Ru(NO)Py ₃Cl(OH)]Cl×1.5H ₂O (I), yield ~55 %. The treatment of the hydroxocomplex I with hydrochloric acid at room temperature gives the aqua complex mer -[Ru(NO)Py ₃Cl(H ₂O)]Cl ₂×2H ₂O×0.5HCl (II). The structures of the compounds have been determined by X-ray crystallography: I - sp. gr. P 2 ₁/ n , a = 9.2292(4), b = 11.7781(4), c = 17.4915(7) Å, β = 90.9560(10)°, R = 4.84%; II - sp. gr. P -1, a = 7.3528(9), b = 11.5793(11), c = 13.6961(16) Å, α = 84.558(3), β = 87.668(4), γ = 74.146(4)°, R = 6.22%. Compounds I and II have been characterized by powder XRD, ¹Н and ¹³С NMR, as well as IR spectroscopy. Thermal decomposition of compound II in inert atmosphere has been examined with thermal analysis.

A new ion-paired compound [4NO ₂BzPy] ₂[Co(NCS) ₄] (1) ([4NO ₂BzPy] ⁺ = 1-(4'-nitrobenzyl)pyridinium, NCS ^- = isothiocyanate) is synthesized and characterized by elemental analysis, IR and UV-Vis spectra, ESI-MS and single crystal X-ray diffraction. Compound 1 is orthorhombic, space group Pbcn, with a = 13.188(2) Å, b = 8.458(1) Å, c = 29.281(4) Å, V = 3266.2(7) Å ³, D _calcd = 1.468 g/cm ³, Z = 4, F(000) = 1476, R ₁ = 0.0332. The [Co(NCS) ₄] ^2- anions form an unusual layer structure by S⋯N and S⋯Co interactions, while the [4NO ₂BzPy] ⁺ cations stack into a 1D column by the p⋯π stacking interaction in the solid state of 1. A magnetic measurement in the range 2-300 K shows a weak antiferromagnetic exchange with θ = -2.42 K in 1.

By treatment of 1,3-bis(3,4-dimethoxybenzyl)-3,4,5,6-tetrahydropyrimidinium chloride (1) with KOBu ^t and [PtCl ₂(PEt ₃) ₂] ₂ N -coordinated platinum complex (2) is obtained. The Pt atom is coordinated in square planar arrangements by two chloride ions in a trans-configuration, the N-formyl- N, N'-bisaryltrimethylenediamine nitrogen atom, and the phosphine P atom. An extensive three-dimensional network of three C-H⋯O hydrogen bonds, two C-H⋯π and one π⋯π interactions are responsible for the crystal stabilization. Intermolecular hydrogen bonds and C-H⋯π interactions produce R ₂ ²(6), R ₂ ²(22), R ₂ ²(24), R ₃ ³(23), R ₄ ⁴(26), and R ₄ ⁴(32) rings.

Polyerther-linked mercury(II) carbene complexes are synthesized by the reaction of carbene precursores with mercury(II) acetate. The binuclear carbene complexes with the chloride ion linkage are easily prepared by the reaction of mononuclear mercury carbene complexes with tetrabutylammoium chloride. The crystal structures reveal that the fluorescence of mercury complexes are related to the coordination mode of the ligands.

The crystal structure of the CL-20 solvate with e-caprolactam in the 1:6 ratio is obtained and studied.

1-Methyl-2-((1 E ,3 E )-4-phenylbuta-1,3-dienyl)pyridinium iodide ( 1) is synthesized and characterized by UV-Vis, FT-IR, ¹H and ¹³C NMR, and single crystal X-ray diffraction. Compound 1 crystallizes in an orthorhombic Iba2 space group with the unit cell parameters a = 12.8236(11) Å, b = 20.1216(17) Å, c = 11.2071(10) Å, V = 2891.8(4) Å ³ and Z = 8. X-ray diffraction indicates that the molecule of 1 displays E , E configurations with respect to the two middle C=C double bonds. The molecular structure of 1 is twisted and the dihedral angle between the pyridinium and phenyl rings is 15.0(2)°. In the crystal packing, cations form stacks in an anti-parallel V-shaped manner along the a axis through π-π interactions between pyridinium and phenyl rings.

The self-assembly of unsymmetrical tecton 3-nitro-5-(pyridin-4-yl)benzoic acid (HL)with cobalt chloride under hydrothermal conditions affords a new 2D coordination polymer [Co(L) ₂] _n ( 1, L = 3-nitro-5-(pyridin-4-yl)benzoate), which is characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction analysis, and single crystal X-ray diffraction. Compound 1 is of the triclinic system, space group P-1 with a = 9.7857(12) Å, b = 10.3417(13) Å, c = 10.8463(13) Å, α = 85.155(2)°, β = 74.785(2)°, γ = 88.962(2)°, V = 1055.4(2) Å ³. The crystal structural analysis of complex 1 shows that the cobalt center is six-coordinated in an octahedral geometry by four O atoms from four different L ligands and two N atoms from two different L ligands; the Co(II) cations are bridged by μ ₃- L into an interesting two-dimensional network structure. It should be pointed out that the thermal analysis results indicate that complex 1 is quite stable up to 420 °C.

This is the first work to synthesize 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione monohydrate, monochloride, mononitrate, and teteraiodotellurate: C ₁₁H ₂₀N ₄O ₂×H ₂O ( I), C ₁₁H ₂₁N ₄O ₂ ⁺×Cl ^- ( II), C ₁₁H ₂₁N ₄O ₂ ⁺×NO ₃ ^- ( III), and 2(C ₁₁H ₂₁N ₄O ₂ ⁺)×TeI ₄ ^2-×C ₃H ₆O ( IV) and determine their structures. Crystals of I are monoclinic: sp. gr. P 2 ₁/ c , at 298 K a = 5.7118(7), b = 17.842(2), and c = 13.5905(16) Å; β = 91.621(11)°; V = 1384.5(3) Å ³; d _x = 1.239 g/cm ³, Z = 4. Crystals of II are tetragonal: sp. gr. P4 ₃, at 298 K a = 6.4134(3) and c = 34.292(2) Å; V = 1410.47(14) Å ³; d _x = 1.303 g/cm ³; Z = 4. Crystals of III are triclinic: sp. gr. P-1, at 298 K a = 8.7614(14), b = 9.3904(18), and c = 10.028(2) Å; α = 63.27(2), β = 78.591(16), and γ = 84.308(15)°; V = 722.3(2) Å ³; d _x = 1.40 g/cm ³; Z = 2. Crystals of IV are triclinic: sp. gr. P -1, at 100 K a = 10.4630(4), b = 11.9372(6), and c = 16.4118(5) Å; α = 72.058(3), β = 76.406(3), and γ = 87.029(3)°; V = 1895.04(12) Å ³; d _x = 2.06 g/cm ³; Z = 2. The synthesis of s- and p-metals with spirocarbone in acetone medium is found to be impossible due to the protonation by the oxygen atom of the carbonyl group. The main crystalline product of the complexation reaction is a monosalt. Evidence is provided that the recrystallization and drying of the synthesized spirocarbone preparation yields monohydrate ( I); its purity and monophasity is confirmed by a Rietveld refinement of the powder X-ray pattern. The lattice parameters at room temperature are: a = 5.6885(12), b = 17.8496(12), and c = 13.518(3) Å; β = 91.449(15)°; V = 1372.1(4) Å ³. The sample is monophasic.

The hydrothermal reaction of CuCN and bpy in the presence of an octahedral cluster complex K _2.75Cs _1.25[Re ₆Se ₈(CN) ₄(OH) ₂]×H ₂O affords a cyanide-bridged chain coordination polymer [CuCN(bpy)] _n (bpy - 2,2’-bipyridyl) ( 1). The structure is monoclinic, space group C 2/ c , a = 22.848(2) Å, b = 7.7182(8) Å, c = 14.4331(13) Å, β = 127.805(2)°, V = 2010.9(3) Å ³, Z = 8, d _x = 1.623 g/cm ³. Copper atoms have a tetrahedral coordination environment formed by N atoms of the bpy molecule as well as N and C atoms of ambidentate bridging CN ligands.

A 1D cadmium (II) coordination polymer {[Cd ₂(L) ₃Cl ₃]×Cl} _n (1) (L = 1,3-bis(benzimidazol-l-yl)-2-propanol) is synthesized by the hydrothermal reaction and characterized by elemental analysis, IR, TG, and X-ray single crystal diffraction. Compound 1 crystallizes in the hexagonal system, space group P 63/ m with a = 15.4857(11) Å, b = 15.4857(11) Å, c = 14.478(2) Å, γ = 120°, V = 3006.8(5) Å ³, Z = 2. In the structure of complex 1, each cadmium center is hexahedrally coordinated by three chlorine atoms and three nitrogen atoms of three distinct L ligands. A detailed analysis reveals that compound 1 exhibits a 1D chain of beads and the adjacent chains are further linked by C-H⋯Cl hydrogen bonding to form a 2D supramolecular framework. Furthermore, the solid-state fluorescent property of 1 is investigated at room temperature.

A new 2D cadmium(II) coordination polymer {[Cd(MBD)(L)]×(H ₂O) ₂} _n ( 1) (H ₂MBD = 5-methoxycarbonyl-benzene-1,3-dicarboxylic acid, L = 1,3-bis(benzimidazol-l-yl)-2-propanol) is synthesized, in which the starting linker (benzene-1,3,5-tricarboxylic acid) undergoes selective monoesterification during the synthesis. In the structure of complex 1, each cadmium center is octahedrally coordinated by four O atoms from three carboxylate groups and two N of distinct L ligands. A detailed structural analysis reveales that compound 1 exhibits a unique 2D binodal (3,5)-connected (4 ².6 ⁷.8)(4 ².6) topology structure. Furthermore, the 2D layer is extended into a 3D network through π-π stacking interactions. The solid-state fluorescence properties of 1 are investigated at room temperature.

An algorithm is proposed to reproducibly obtain single crystals of salts and mixed crystals of amino acids with dicarboxylic acids and other small organic molecules. The resulting crystals are of high quality and have good faceting, which makes them suitable for single-crystal XRD and Raman spectroscopic (including polarized radiation) experiments. The ease of the implementation and the possibility to reproduce the crystallization using equipment and materials that are available at virtually every laboratory are the hallmarks of the proposed algorithm, which involves two stages of work. During the first stage, the original components are screened, quickly and easily, to find new phases. The aim of the second stage is to obtain single crystals that meet the requirements of different research methods. An ideal case is the one whereby it is possible to control the size of well-faceted spaced apart crystals that grow within a few hours and are easy to separate from the surface.

Nanostructured carbon-silica composite materials are prepared from different compounds in one-pot. They are characterized by BET, transmission electron microscopy, X-ray diffraction, and small-angle X-ray scattering. An effective method of the quantitative analysis of the structural dispersed characteristics of the template phase of silica in these composites is proposed.

X-ray photoelectron spectroscopy is used to study the interaction of model NO ₂ storage-reduction catalysts (NSR catalysts) Ba/TiO ₂ and Ba/ZrO ₂ with NO ₂. The catalysts are prepared on the surface of ultrathin Al ₂O ₃ film substrates obtained by the FeCrAl alloy oxidation. It is shown that at room temperature the model catalysts react with NO ₂ with the successive formation of surface barium nitrite and nitrate. The NO ₂ reduction with the formation of barium nitrite at the initial step of the interaction is assumed to be accompanied by the oxidation of residual metallic barium and amorphous carbon impurity. It is found that the formation of barium nitrate proceeds more efficiently on Ba/ZrO ₂ rather than on Ba/TiO ₂.

The mineral and microelement composition of natural manganese minerals from iron-manganese concretions of the Bol’shoe Miassovo lake (South Ural) is investigated. The structural transformations of the samples under the effect of different temperatures are studied. Apart from layered 9.6 Å and 7.2 Å structures of manganese minerals the lake samples often contain various manganese-containing carbonates. For carbonate minerals by IR spectroscopy the dependence of the wavenumbers of n ₂ and n ₄ vibrations of the СО ₃ group on the mineral composition is analyzed. The composition of macro- and microelements of iron-manganese concretions of Bol’shoe Miassovo lake varies in wide ranges not only in different samples, but also in different parts of the same sample. An analysis of the microstructure of lake manganese concretions revealed their biomorphic nature that is exhibited in globe-shaped to filament organic bacterial forms.

The thermal stability of cation-ordered perovskite-like layered titanates ANdTiO ₄ and A ₂Nd ₂Ti ₃O ₁₀ (A = Na, K) is studied in the temperature range of 900-1400°C. The structural chemical mechanism of their thermal decomposition is established. A comparative analysis of the thermal stability of compounds with different thicknesses of the perovskite layer and different nature of the alkali cation is performed. The observed thermal behavior is explained from crystal chemical standpoints.

Mineralogical and crystallochemical studies of endogenic carbonates from bottom sediments of some shalllow saline lakes of Western Transbaikalia are performed. X-ray diffraction (XRD), IR spectroscopy, electron microscopy, elemental analysis (SR XFA), analysis of stable δ ¹⁸O and δ ¹³С isotopes, and other methods are applied. By modeling the complex XRD profiles by means of the Pearson VII function Mg-calcites with different Mg concentrations and Сa-excess dolomites are found in the assemblage of carbonate minerals. It is shown that in a series of Mg-calcites there is a gap in the region 2θ Cu K _a = 30°, which is caused by a transition from the structures representing true solid solutions to the structures of layered “domain” nanosized crystals. The idea of excess-Са dolomite as the extreme member of the Mg-calcite series is substantiated. The carbonate record containing data on the stratigraphical distribution of endogenic carbonates of the calcite-dolomite series is obtained. The amount and ratio of phases with different Mg concentrations in this series are determined by the value of the Mg/Ca ratio, the total salinity and alkalinity of lake waters in the past, changing in accordance with climate cycles and fluctuations of the lake level.

The possibility of a simultaneous use of X-ray diffraction and X-ray absorption techniques in order to characterize the sizes, shapes, and chemical composition of grains in a sample (the solution of the extended uncertainty problem due to the Babinet principle) is shown. A sample of the GaAs _0.7Se _0.3/GaAs solid solution is investigated on the developed laboratory device for a simultaneous performance of X-ray diffraction and X-ray absorption experiments. It is shown that the GaAs _0.7Se _0.3 sample decomposes into separate GaAs and GaSe domains forming a mosaic structure. The sizes of GaAs and GaSe domains are estimated. Components with a linear geometry are sometimes revealed in the composition of GaSe grains.

The combined use of different synchrotron radiation (SR) X-ray diffraction techniques is shown to be effective in collecting the most complete structural information about an object being studied. The high intensity of SR and its spectral-angular distribution enable researchers to conduct experiments with high angular resolution, experiments using resonance effects, time-resolved experiments, and experiments where the sample is exposed to the effects of temperature and reaction medium. Results are presented of two studies where the distinctive features of SR play the key role.