Home – Home – Jornals – 2013 number 3

By the example of the structure of phenanthrene the character of the H–H interaction is studied by non-empirical quantum chemical methods. The calculations performed confirm Bader’s conclusions about the attractive character of the H–H interaction, which were made based on the QTAIM analysis, and disprove the repulsive character of the above interaction, which was derived from the EDA procedure.

DFT and HF methods using the PC GAMESS-Firefly program are employed to calculate the spatial and electronic structures of molecules: alkoxy derivatives of aluminum. By NBO and AIM methods the main characteristics of Al–O, C–O, and Al–X bonds in these molecules are determined. It is shown that Al and О atoms interact with each other as atoms with closed shells. The С–O bonds are close to covalent, whereas the Al–X bonds are the intermediate type bonds.

By the density functional method (B3LYP/6-31++G(d,p)) optimal structures of proton hetero and homo disolvates involving water molecules, ethyl formate, methyl acetate and products of their hydrolysis are calculated. The data on the structure of these ions and the strength of their H bonds are analyzed together with the results of a similar calculation previously performed for methyl formate. It is shown that in proton solvation by two molecules present in the solution during the hydrolysis of ethyl formate, methyl acetate, and methyl formate stable (X⋯H⋯X)⁺ or (X⋯H⋯Y)⁺ particles form. Structural and energy parameters of their O⋯H⋯O bridges obey the same regularities and are mainly determined by a difference in the proton affinity of X and Y molecules. Calculation results are compared to the data of a number of experimental studies of the acid hydrolysis of esters.

The geometries of ten benzenoid energetic materials are fully optimized by employing B3LYP and B3P86 methods with the 6-31G** basis set. Bond dissociation energies (BDEs) for the removal of the NO₂ group in benzenoid molecules are calculated at the same level. The calculation results show that the insertion of an electron withdrawing group increases the stability of the molecules, while the insertion of an electron donating group reduces the stability of the molecules. In addition, the relationship between the impact sensitivities and the weakest BDE values is examined. There exists a good linear correlation between the impact sensitivity and the ratio of the BDE value to the molecular total energy.

As a result of a joint interpretation of mass spectra and gas chromatographic retention indices more than ten products of free radical chlorination of methyl-tert-butyl ketone are identified. They contain from one to six chlorine atoms in the molecule and were not previously characterized either by mass spectrometric or chromatographic reference data. It is found that retention index increments corresponding to a gradual increase in the number of chlorine atoms in the molecule per unit are non-additive and vary in wide ranges (from 53 i.u. to 219 i.u.), which does not hinder the use of separate elements of additive schemes for the estimation of the indices of products of such non-regioselective reactions.

X-ray photoelectron spectroscopy (XPS) and density functional theory are employed to study the electronic structure of octasilsesquioxanes (RSiO_1.5)₈ with vinyl and phenyl terminal groups. Quantitative compositions determined from the XPS data are close to those estimated by empirical formulas. Narrow spectral lines corresponding to ionization from C1s core levels indicate similar chemical states of carbon atoms for both compounds. Experimental data are confirmed by close calculated values of effective charges on carbon atoms when polarization functions are included in the basis set and also by small energy ranges of core level electrons. The valence spectral region is interpreted based on the calculated energy values of electronic levels with regard to the density of states and ionization cross-sections.

Reaction of dinuclear platinum(II) sulfido complex [Pt₂(µ-S)₂(PPh₃)₄] with 1,3-propanesultone gives the novel zwitterionic monoalkylated thiolate complex [Pt₂(µ-S){µ-S(CH₂)₃SO₃}×(PPh₃)₄], which was characterized by NMR spectroscopy, electrospray ionisation mass spectrometry, and a single crystal X-ray structure determination. Crystals are monoclinic, space group P2(1)/ c with unit cell dimensions a = 16.8957(3) Å, b = 15.5031(3) Å, c = 28.0121(5) Å, β = 99.780(1)°, for Z = 4.

Thermodynamic characteristics of aqueous linear diol solutions are calculated. These data are used to identify regularities in the variations of the structural properties of the mixtures being studied. The correlation between the entropy and enthalpy characteristics of water–diol systems with excess packing coefficients is evidence that the structural and energy properties of aqueous linear diol solutions are determined by universal interactions. The form of the concentration dependences of the solvation enthalpies and entropies of noble gases in water–linear diols mixtures is determined by the reorganization component and is attributed to the destruction of the H bond network of water, which results in the formation of the most densely packed solutions in the medium range of compositions.

The dependence of the standard partial volumes of glycine, a-alanine, and serine on the ionic strength of aqueous sodium chloride and sulfate solutions is modeled by the extended Masson equation: V⁰ = V_w⁰ + AI^0,5 + BI. The error of less than 0.2 cm³/mol is a result of using five values of the А and В parameters: the two values of А are determined by the type of salt and the three values of В by the type of amino acid. A new variation of the additive-group approach is proposed for ΔV⁰ = V⁰ - V_w⁰. The partial volumes of the СН₃ group (a-alanine) and the СН₂ group (serine) are found not to depend on the salt concentration. The partial volume of the СН₂ group of glycine grows with concentration. The structural characteristics of the hydrated complexes of the NH₃⁺ and COO^- groups are calculated: the hydration numbers, the molar volumes of water inside and outside the hydration sphere, and the intrinsic volume of NH₃⁺ in COO^- in solution. Given the same ionic strength, the aqueous sodium sulfate solution produces a somewhat stronger dehydration of the charged groups.

The monoclinic modification of ZrF₄×3H₂O, isostructural to HfF₄×3H₂O, is synthesized and structurally studied for the first time. Unlike the triclinic modification of ZrF₄×3H₂O with a dimeric structure, the synthesized compound has a polymer structure formed from infinite chains composed of ZrF₆(H₂O)₂ groups sharing F…F edges. The crystal structure of HfF₄×3H₂O, previously determined by the photo method, is refined. The refined data on the geometric characteristics of the coordination polyhedron of the Hf atom and the system of hydrogen bonds in the structure are obtained.

Single crystals of a new compound containing triphenylguanidinium and bis(dicarbollide)nickel(III) [C(NHC₆H₅)₃][Ni(B₉C₂H₁₁) ₂] are obtained and analyzed by LOW-TEMPERATURE. Crystallographic data are: C₂₃H₄₀B₁₈N₃Ni, M = 611.87, monoclinic system, space group P2₁/с, unit cell parameters: a = 21.9085(5) Å, b = 19.9294(4) Å, c = 14.8721(4) Å, β = 91.4033(9)°, V = 6491,5(4) ų, Z = 8, d_x = 1.252 g/cm³, T = 100 K, F(000) = 2536, μ = 0.621 mm^–1. The structure was solved by direct and Fourier methods and refined by the full matrix least squares technique in the anisotropic/isotropic (for H atoms) approximation up to the final factor R₁ = 0.053 for 10429 I_hkl ≥ 2σ_I (Bruker X8 APEX diffractometer, MoK_α radiation). It contains two independent [C(NHC₆H₅)₃]⁺ cations with different conformations and two [Ni(B₉C₂H₁₁)₂]^– anions with the same transoid conformation. Three types of weak intermolecular interactions are found: N–H^δ+⋯^δ–H–B; C–H⋯π between the H(C) atoms of cluster anions and delocalized π systems of Ph rings of cations; π⋯π interactions of Ph rings of cation 2 with each other.

A new cadmium(II) complex with (1'H-[2,2']Biimidazoly-1-yl)-acetic acid (HBDAC) [Cd(BDAC)₂(H₂O)₂]×H₂O is synthesized and structurally characterized, which crystallizes in the monoclinic system, space group P2₁/c , a = 8.465(3) Å, b = 14.164(5) Å, c = 11.294(3) Å, α = 90°, β = 127.405(17)°, γ = 90°, Z = 2. The [Cd(BDAC)₂(H₂O)₂]·H₂O units are further bridged by O—H^…O, N—H^…O, C—H^…O hydrogen bonds, π—π stacking and C—O^…π interactions, generating a three-dimensional supramolecular structure. In addition, luminescence measurements reveal that complex 1 exhibits strong fluorescent emission in the solid state at room temperature.

Molecular and crystal structures are determined for amino-substituted nitronyl nitroxide 1, the products of its subsequent oxidation, acylation, and reduction: zwitter-ions 3a, 3b and salts K(4b) and K₂(4b)(CF₃CO₂).

The crystal and molecular structure of potassium thiobarbiturate C₄H₃KN₂O₂S (C₄H₄N₂O₂S–2-thiobarbituric acid, H₂TBA) is determined. Crystallographic data for KHTBA are as follows: a = 11.2317(17) Å, b = 3.8687(6) Å, c = 14.557(2) Å, β = 97.448(4)°, V = 627.18(17) ų, space group P2/c , Z = 4. Each potassium ion is linked with four oxygen atoms and two S atoms forming a distorted octahedron. N–H⋯O and C–H⋯S hydrogen bonds form a branched three-dimensional network. The structure is also stabilized by the π–π interaction of heterocyclic HTBA^– ions.

A 4,4'-bipyridine Zn(II) complex [Zn(4,4'-bipy)₂(H₂O)₄](ClO₄)₂×4(4,4'-bipy) is synthesized, characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR spectroscopy, and studied by X-ray crystallography. The compound forms monomeric units as a result of unusual unidentate coordination of 4,4'-bipy ligands. The thermal stability of the compound is studied by thermal analyses. Furthermore, the complex is luminescent with emission maxima at 329 nm in the methanol solvent. Different sizes of zinc(II) oxide nanoparticles are prepared by calcination of the [Zn(4,4'-bipy)₂(H₂O)₄](ClO₄)₂×4(4,4'-bipy) compound at two different temperatures. These nanostructures are characterized by X-ray powder diffraction and scanning electron microscopy.

The crystal structure of {aquaimidazole[2-(2-carbamoylhydrazone)-propionato]}copper(II) nitrate [Cu(L)Im(H₂O)]NO₃ (I), where HL is the semicarbazone of pyruvic acid, Im is imidazole, is dtermined. The crystal structure of I contains two independent complexes IА and IВ in which copper atoms coordinate once deprotonated tridentate НL, imidazole, and water molecules. Outer spheres of the complexes contain nitrate ions. In the compounds studied the coordination polyhedron of the copper atom is a distorted tetragonal pyramid. Its base is composed of carboxyl and carbamide oxygen atoms, azomethine nitrogen of monodeprotonated HL molecules, and the imidazole nitrogen atom. In the crystal, nitrate ions and imidazole molecules link the complexes via hydrogen bonds into 2D networks parallel to the (010) plane. These networks in turn are in pairs arranged into layers along the [010] direction due to hydrogen bonds between water molecules and oxygen atoms of nitrate ions, and also by water molecules and O3 atoms of the neighboring 2D networks. In the crystal, the π–π stacking interaction is observed between the imidazole rings from different layers and there is also a N–O⋯Cg (π ring) interaction inside the layers.

Two new isostructural methoxide-bridged dimeric oxovanadium(V) complexes [VO(L¹)(OMe)]₂ (1) and [VO(L²)(OMe)]₂ (2), where L¹ and L² are the deprotonated forms of 3-bromo- N'-[1-(2-hydroxyphenyl)ethylidene]benzohydrazide (H₂L¹) and 3-chloro-N '-[1-(2-hydroxyphenyl)ethylidene]benzohydrazide (H₂L²) respectively, are synthesized and characterized by elemental analyses, IR spectra, and single crystal X-ray determination. Both crystals crystallize in the triclinic space group P-1. For 1, a = 7.5237(15) Å, b = 10.846(3) Å, c = 11.195(3) Å, α = 84.143(3)°, β = 72.244(3)°, γ = 77.869(3)°, V = 849.9(4) ų, Z = 1, R₁ = 0.0634, wR₂ = 0.1373. For 2, a = 7.493(2) Å, b = 10.740(3) Å, c = 11.109(3) Å, α = 84.569(2)°, β = 71.783(2)°, γ = 79.822(2)°, V = 835.0(4) ų, Z = 1, R₁ = 0.0511, wR₂ = 0.1076. Each V atom in the complexes is octahedrally coordinated.

Two new zinc(II) complexes [ZnL(N ₃)]×BF ₄ (1) and [ZnBrL]×BF ₄ (2), derived from the tetradentate Schiff base ligand N,N'-bis(1-pyridin-2-yl-ethylidene)propane-1,3-diamine (L), are prepared and characterized by physicochemical methods and single crystal X-ray crystallography. The crystal of (1) is triclinic: space group P-1, a = 8.593(1) Å, b = 8.752(1) Å, c = 13.393(2) Å, α = 97.153(1)°, β = 93.046(1)°, γ = 91.577(1)°, V = 997.4(2) ų, Z = 2. The crystal of (2) is triclinic: space group P-1, a = 8.351(1) Å, b = 8.956(1) Å, c = 13.139(2) Å, α = 92.716(1)°, β = 94.241(2)°, γ = 95.016(1)°, V = 974.8(2) Å ³, Z = 2. The geometries of the penta-coordinated zinc atoms in both complexes are intermediate between the square pyramid and the trigonal bipyramid having the Addison parameters of 0.39 and 0.47 respectively. The syntheses of the complexes show distinct preference for the anions in the order Br^– >N₃^–> CH₃COO^–.

bis-Isonicotinoyl hydrazone of 2,5-diformylpyrrole existing in the crystal in the form of a tetrahydrate of the hydrazone tautomeric form is synthesized and its structure is described. In the crystal, an infinite three-dimensional network of hydrogen bonds is formed by hydrazone molecules. The neighboring hydrazone molecules are bonded by intermolecular π stacking interactions. A quantum chemical calculation of the geometry and total energy of possible tautomers in vacuum and an aqueous solution is performed.

We study the interaction of dialkyl substituted and cyclic cadmium dithiocarbamates with [AuCl₄]^– anions in 2M HCl medium. The state of the chemisorbents upon contact with AuCl₃ solutions is controlled by ¹¹³Cd MAS NMR spectroscopy. The result of the heterogeneous reactions involving chemisorption binding of gold(III) from the solutions and partial ion exchange is the formation of heteropolynuclear gold(III)–cadmium complexes. The crystal and molecular structure of the acetone-solvated form of polymeric bis-(N,N-diethyldithiocarbamato-S,S') gold(III) hexachlorodicadmate is identified by single-crystal XRD. The main structural moieties of the compound are complex [Au{S₂CN(C₂H₅)₂}₂]⁺ cations and [Cd₂Cl₆]^2– anions. The structural self-organization of the complex at the supramolecular level is attributed to the secondary Au⋯S bonds between neighboring isomeric complex gold(III) cations; the bonding results in the formation of linear polymer ([Au{S₂CN(C₂H₅)₂}₂]⁺)_n chains, with [Cd₂Cl₆]^2– anions alternating to the right and left of the chains.

New (C₁₇H₂₀FN₃O₃)₂[CoCl₄]₂×3H₂O (I) and C₁₇H₂₀FN₃O₃[CoCl₄]×H₂O (II) compounds, where C₁₇H₁₈FN₃O₃ is ciprofloxacin (CfH), are synthesized and their crystal structures are determined. Crystallographic data for I: a = 18.441(5) Å, b = 9.030(3) Å, c = 27.551(8) Å, V = 4588(4) ų, space group Pca2₁, Z = 4; for II: a = 9.305(3) Å, b = 9.885(3) Å, c = 12.999(4) Å, α = 82.782(4)°, β = 72.954(4)°, γ = 89.736(4)°, V = 1133(1) ų, P–1 space group, Z = 2. Both structures contain CfH₃²⁺ ion pairs bonded by the π–π interaction. Additionally, in the crystal of I there is a stacking interaction between the π clouds of aromatic rings and hydrogen atoms of the cyclopropyl group linking the pairs of molecules with each other. The structure of the centrosymmetric crystal of triclinic phase II is also formed from CfH₃²⁺ ion pairs bonded by the π–π interaction, which, in this case, are not independent because they are related by the symmetry center. Hydrogen bonds form a branched three-dimensional network linking the CfH₃²⁺ and CoCl₄^2– ions and water molecules.

A new trinuclear Ni(II) complex {[NiL(DMF)]₂(OAc)₂Ni}×2DMF (H₂L = 4,4'-dichloro-2,2'-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol) is synthesized and characterized by elemental analyses, IR spectra, UV—Vis spectra and X-ray crystallography. The results show that the Ni(II) complex consists of three Ni(II) ions, two tetradentate (μ-L)^2– units, two coordinated μ-acetate ions, two coordinated DMF molecules, and two crystallization DMF molecules. All hexacoordinated Ni(II) ions of the complex have a slightly distorted octahedral geometry. The crystal packing of the Ni(II) complex reveals a notable feature of this structure: the formation of an infinite supramolecular 2D layered structure by virtue of intermolecular C—H⋯O hydrogen bonding.

Phthalazinylhydrazone of 2-formylpyrrole is synthesized, the values of ionization constants are determined, and quantum chemical calculation of the geometry and total energy of possible tautomers is performed. The structure of the cyclic oxidation product of hydrazone 3-(1H-pyrrolyl-2)-[1,2,4]-triazolo(3,4-a)phthalazine existing in the crystal in the form of dimers linked by two hydrogen bonds is described.

A new Schiff base cobalt(III) complex with the formula [CoL¹L²(N₃)]×NO₃ (L¹ is 2-[1-(2-phenylaminoethylimino)ethyl]phenolate, L² is N-phenylethane-1,2-diamine) is prepared and characterized by physicochemical methods and single crystal X-ray determination. The complex crystallizes in the triclinic system space group P-1, with a = 8.504(2) Å, b = 14.973(3) Å, c = 20.676(4) Å, α = 100.021(3)°, β = 90.005(3)°, γ = 103.084(2)°, V = 2523.0(9) ų, Z = 4, R₁ = 0.0732, and wR₂ = 0.1182. Single crystal X-ray diffraction analysis reveals that the complex contains two mononuclear [CoL¹L²(N₃)]⁺ cations and two nitrate anions. The Co atom is six-coordinated in an octahedral geometry. The ligands and the cobalt(III) complex are screened in vitro for their antibacterial activity against Bacillus subtillis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aereuguinosa.

Molecular and crystal structures of dimephosphone nicotinoylhydrazone and dimephosphone iso-nicotinoylhydrazone exhibiting antiphthisic activity are studied. In contrast to aroylhydrazones of arylaldehydes, existing in the crystalline state as a mixture of two amide conformers, the studied hydrazones exist in the crystalline state in the single geometrical form E_C=NE_N—NZ_N—C(О).

The origin of the magnetic field effect on the dimerization of aluminum(III) and gallium(III) phthalocyanine chloride films is revealed. The EPR technique is employed to demonstrate that the dimerization of the above coordination compounds occurs via a free radical pathway with the formation of phthalocyanine and OH radicals, thus resulting in the appearance of the magnetic moment in the studied compounds.

[Pt₃S₂(P(CH₂OH)₃)₆](PF₆)(OH)×H₂O (1) is obtained by a reaction of [Pt₃S₂(P(CH₂OH)₃)₆]Cl₂ with NH₄PF₆. The crystal structure of 1 was determined by a single crystal X-ray diffraction analysis (space group R3c a = 12.0042(2) Å, c = 52.6879(11) Å, V = 6575.2(2), Z = 6, C₁₈H₅₇F₆O₂₀P₇Pt₃S₂, d_x = 2.385 g/cm³, T = 150 K, R₁ = 0.044 for 2123 F₀ > 4δ(F) until 2θ_max = 63°). The cations contain a {Pt₃(μ₃-S)₂}²⁺ core with nonbonding Pt…Pt distances of 3.1536(6) Å. The Pt atoms are in a square planar environment; the Pt–S and Pt–P bond lengths are 2.3586(16) Å and 2.260(2) Å respectively.

Single crystal X-ray diffraction is used to determine the crystal structure and conformational features of 9-(furan-2-yl)-4,5,6,7,8,9-hexahydro[1,2,3,4]tetrazolo[5,1-b]quinazoline obtained by three-component cyclocondensation of furfurol, 5-amino-1Н-1,2,3,4-tetrazole, and cyclohexanone.

The title compound C₂₄H₂₂ClNO₂ belongs to the orthorhombic system, space group Pca2₁ with a = 12.1771(10) Å, b = 4.9305(4) Å, c = 34.419(3) Å, α = β = γ = 90°, V = 2066.5(3) ų, Z = 4, D_c = 1.260 g/cm³, F(000) = 824, R = 0.0402 and wR = 0.1144, S = 1.034, T = 293 K. The compound is a chalcone with 4-chlorophenyl and [(5-ethyl-pyridin-2-yl)-ethoxy]-phenyl substituents bonded at the opposite ends of a propenone group, the biologically active region. The propenone bridge makes dihedral angles of 10.61(23)° and 62.75(22)° respectively, with 4-chlorophenyl and the [(5-ethyl-pyridin-2-yl)-ethoxy]-phenyl group.

A co-crystal is obtained in a methanolic solution from methyl 2-(3-chloro-4-methyl-2-oxo-2H-chromen-7-yloxy)acetate and 2-(2-aminophenyl)benzothiazole. In the crystal these molecules are connected via usual N—H…O and weak C—H…O H-bonds. The co-crystals are very stable.