Том 57, № 4 (2016)

The atomic structure of the highest molecular orbitals (MO) of small tetra-heme cytochrome (STC) c 1M1P is studied in large-scale ab initio all-electrons Hartree–Fock calculations. It is shown that the highest MOs of STC are mainly formed by atomic orbitals of negatively charged amino acid atoms whose types and corresponding numbers are determined. The results obtained permit the conclusion that these amino acids can be considered as possible active centers in the electron transfer reaction between STC and an external electron acceptor.

The structure and electrical properties of open carbon nanotube with chirality (4,4), consisting of 5-15 segments, are calculated within four quantum chemical models: AM1, PM3, LSDA/3-21G*, and B3LYP/6-31G. Size effects and the effect of the model choice on the geometry, energy, enthalpy and Gibbs energy of the formation (atomization), Mulliken atomic charges, polarizability, and predicted adsorption properties of nanotubes are discussed.

The article presents the results of EPR studies of Pb₂MoO₅ crystals containing a copper impurity. Based on the analysis of angular dependences of the EPR spectra, it is found that copper ions incorporate into the structure of the Pb₂MoO₅ crystal in the Cu²⁺ state and occupy the molybdenum site with the formation of a linear extended Cu(II)–V(O)–Pb(IV) defect along the а axis of the crystal. An oxygen vacancy appears in the structure of the defect to compensate the charge and the lead ion acquires the Pb⁴⁺ charge state. According to the structure of this center, one magnetically non-equivalent position with the direction of main values of А and g of A(Cu)_zz and g_zz tensors parallel to the а axis is observed in the EPR spectra. Moreover, the EPR spectra exhibit an addition hyperfine structure from one lead atom on which the unpaired electron density is 0.061%. The obtained data on the structure of the defect formed when the copper impurity incorporates into the Pb₂MoO₅ crystal provided the assumption that the observed light scattering when the light beam is directed perpendicular to the а axis may be due to the cooperative effect of the presence of di- and tetravalent ions substituting for molybdenum in the linear configuration of Pb–O–Mo bonds.

A new potassium cadmium hydrogen diphosphate dihydrate, KCdHP₂O₇∙2H₂O (1), has been synthesized by slow evaporation at room temperature and characterized by FT-IR, Raman, TG-DTA, and single crystal X-ray diffraction. Compound (1) crystallizes in the orthorhombic Pcmn space group with the unit cell parameters a = 6.5814(8) Å, b = 7.9428(9) Å, c = 15.961(6) Å, V = 834.4(3) Å3 and Z = 4. Its structure consists of polyhedral layers parallel to the ab plane where each CdO₆ octahedron (m position) shares four edges with three different diphosphate groups. In the Cd octahedron, two oxygen atoms residing in (m) special positions belong to coordinated water molecules. These layers are joint by K⁺ cations (4c Wyckoff position) and hydrogen bonds, leading thus to a two-dimensional framework. The structural model is supported by the bond-valence-sum validation tool as calculated valences are close to the formal oxidation numbers.

The calorimetric method at temperatures of 288 K, 298 K, and 313 K is used to measure the heats of dissolution of L-α-alanine in aqueous NaCl (m ≤ 5 mol/kg water) and KCl (m ≤ 4 mol/kg water) solutions. The enthalpy and heat capacity coefficients are determined for the pair and triple interactions of alanine with nonaqueous components. Literature data is used to find the contributions from the charged NH₃⁺ and COO^– groups and the hydrocarbon radicals СНСН₃ of L-alanine and СН₂ of glycine in mixtures of water with NaCl, KCl, and urea. A discussion is given of the impact of additives and temperature on the interactions of hydrophilic and hydrophobic amino acids in the said systems.

The crystallographic analysis of Bi₂S₃, CuPbBi₅S₉, CuPbBi₃S₆, and CuPbBiS₃ compounds, representing a series with a successive replacement of a part of Bi atoms by Pb+Cu, shows that they are characterized by a stable combination of a pseudotetragonal cation framework with a pseudohexagonal anion one, which is common for all structures, within orthorhombic unit cells with n sizes of 11.2 Å, 4 Å, and 11.5 Å. The Bi₂S₃ cation framework is retained for the heavy Bi+Pb, and additional light Cu fill the available vacant sites without changing its geometry but varying the crystallographic symmetry within the orthorhombic crystal symmetry and unit cells of n standard blocks (11.2×4×11.5 ų).

Three new salts of the {[Ca(H₂O)]₆[P₄W₆O₃₄]₂}^12– polyanion, namely (NH₄)₁₂{[Ca(H₂O)]₆∙[P₄W₆O₃₄]₂}∙ ∙24H₂O (1), H₂[Na(H₂O)_1.6]₁₀{[Ca(H₂O)]₆[P₄W₆O₃₄]₂}∙10H₂O (2), and [Ca(H₂O)₅]₆{[Ca(H₂O)]₆∙ ∙[P₄W₆O₃₄]₂}∙11H₂O (3) are prepared. The change in the lattice as a function of the countercation and its coordination, specially calcium, is investigated. Full characterization is made by single crystal X-ray diffraction and also UV-visible spectroscopy, FT-IR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS).

The μ-oxo-bridged Fe(III) dimer complex [{Fe(4-MeOL1)}₂(μ-O)]∙HOCH₃, (H₂-4-MeOL1 = N,N′-bis(4-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine), 1 is synthesized and characterized by single crystal X-ray diffraction. Complex 1 contains a [{Fe(4-MeOL1)}2(μ-O)] dimeric unit with a methanol solvent molecule of crystallization. Each Fe(III) ion has a distorted square-pyramidal coordination geometry. In the basal plane, the Fe(III) atom is coordinated by two N and two O atoms of the Schiff base ligand. The apical position is occupied by a bridging O^2– ion, linking another Fe(III) ion in the complex. There are intermolecular C–H…O and C–H…π interactions among the dinuclear complexes.

Hydrothermal syntheses of 2-carboxyethyl(phenyl)phosphinic acid (H₂CEPPA) with Bi(NO₃)₃ and Cd(NO₃)₂ produce two layered complexes [Bi₂(μ₃-O)(CEPPA)₂]_n (1) and [Cd(HCEPPA)₂]_n (2). Compound 1 is comprised of [Bi₄(μ₃-O)₂(POO)₄(COO)₄] SBUs which grow into a double wave-like 2D layer with–CH₂CH₂–spacers. Compound 2 crystallizes in the orthorhombic noncentrosymmetric space group Pca2₁, exhibiting a double lattice-like layer. Through edge-to-face d∙∙∙π stacking, a 3D supramolecular framework is formed based on 2D lattices. Topological analyses indicate that 1 and 2 have sql (or Shubnikov tetragonal plane net) and kgd (or Shubnikov (3.6.3.6) plane net) topological networks respectively. 1 and 2 are isolated as single crystal pure phases, which is confirmed by powder XRD. TGA shows high thermal stabilities with decomposition temperatures of 1 and 2 being 373 and 303°C respectively. The fluorescent spectra exhibit fluorescence quenching in 1 and sharp emission at 292 nm in 2, which is assigned to intraligand emission.

The molecular and crystal structure of 1,2-bis(methyl-ONN-azoxy-oxy)ethane is studied. Its molecule has a gauche conformation with respect to the C–C bond with a torsion angle of 71.4°.

New approaches to the analysis of small-angle X-ray scattering data from nanoscale systems based on the optimization and direct multiple shooting methods are presented. A program is developed, which bears on these new approaches and allows a user to model small-angle X-ray diffraction data, introduce collimation corrections, and analyze dispersions in the samples. The program results for a number of typical nanosized systems (sols, catalysts) are reported and the comparison with currently available programs for small-angle data processing is presented.

A new titanium complex [Ti(Me–Q)₂(Cl)₂] (1) is prepared by reacting titanium tetrachloride with 2-methyl-8-hydroxyquinoline in a fast and facile process. The complex is fully characterized based on its ¹H and ¹³C NMR, IR, and UV spectra and elemental analysis. The prepared nanostructured compound is synthesized by the sonochemical method. This new nanostructure is characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), IR spectroscopy, and elemental analysis. Thermal stability of single crystalline and nanosize samples of the prepared compound is studied by thermal gravimetric (TG) and differential thermal analysis (DTA). The prepared complexes both bulk and nanosized are utilized as a precursor for the preparation of TiO₂ nanoparticles by direct thermal decomposition at 600°C in air. The morphology and size of TiO₂ nanoparticles are determined by SEM, powder XRD, and IR spectroscopy and the results show that the TiO₂ nanoparticle size depends on the initial particle size of 1. Photoluminescence (PL) properties of the nanostructured and crystalline bulk prepared complex and their TiO₂ nanoparticle cores are investigated.

Features of the electronic structure of layered ZrCuSiAs-like LaZnAsO_1–δ phases at δ = 0.11 and 0.44 are briefly discussed based on the results of ab initio calculations. It is shown that the effect of oxygen vacancies on the electronic structure of non-stoichiometric phases is equivalent to the effect of an electron dopant and the charge compensation occurs inside [La–O] structural blocks due to variation of the occupation of lanthanum electronic states.

Water uptake by dry Lima beans (Phaseolus limensis L.) was traced using 1H micro-magnetic resonance imaging. The studies are performed using two-dimensional longitudinal images. Channels through which water comes in an imbibing bean seed are determined; the water distribution inside the seed is shown to be heterogeneous.

A new complex of copper (II) with 3-(2-hydroxy-3-sulfo-5-nitrophenylazo)-pentadione-2,4 (HL) is synthesized and analyzed by single crystal XRD. The crystals are monoclinic: a = 7.7563(4) Å, b = 24.0157(12) Å, c = 24.6353(13) Å, β = 91.9490(10)°, V = 4586.2(4) ų, space group P2₁/c, Z = 2, ρ_calc = 1.713 g/cm³, R = 0.0695. The environment of the copper atom is formed by three oxygen atoms, the nitrogen atom of tetradentate ligand, and the oxygen atom of a water molecule.

The structure of ruthenium(III) dipivaloylmethanate is determined by single crystal X-ray diffraction at temperature of 150 K. The crystallographic data for C₃₃H₅₇O₆Ru are as follows: a = 9.6119(11) Å, b = 17.4603(19) Å, c = 21.519(2) Å, β = 95.187(2)°, C2/c space group, V = 3596.7(7) ų, Z = 4, d_calc = = 1.202 g/cm³, R = 0.0642. The structure is molecular, the metal atom coordinates six oxygen atoms of three ligands of β-diketone. The Ru–O distances are in the range of 1.99 Å to2.03 Å. The complexes have a distorted single layer hexagonal packing with the Ru…Ru distances being 9.84 Å within the layer, and 10.93 Å between the layers.

The preparation of a cobalt(II) chloride complex with a N-donor ligand 1-benzyl-5-methyl-1H-imidazole of formula [CoCl₂(1-benzyl-5-methyl-1H-imidazole)₂] is described. The isolated complex was characterized by UV, IR spectroscopy and crystallographic studies. Single crystal X-ray diffraction analysis of the complex reveals its monomeric tetra-coordinated nature. The coordination polyhedron around the cobalt center can be described as a quasi-regular tetrahedron. The Co–N distances for this compound are 2.0111(17) Å and 2.0118(17) Å, while the Co–Cl distances are 2.2582(7) Å and 2.2549(7) Å. The crystal packing can be described as layers parallel to (101) plane alternating along the b axis, and it is stabilized by π–π stacking between the imidazole and phenyl rings. The shortest centroid–centroid distance is 3.6002(14) Å.

Di-μ-amido-bis[diammineplatinum(II)] nitrate (1) was synthesized as a byproduct during preparation of tetraammineplatinum(II) nitrate. One possible pathway to produce 1 is that [(H₃N)₂Pt(μ- OH)₂Pt(NH₃)₂](NO₃)₂, a well-known complex forming on treatment of cis-Pt(NH₃)₂I₂ with AgNO₃, reacts with aqueous ammonia. The other possible pathway involves deprotonation of [Pt(NH₃)₄](NO₃)₂ to form monomeric Pt(NH₃)₃(NH₂)NO₃ followed by elimination of NH3. Crystals of 1 (from water) are monoclinic (C2/c) with a = 16.834(2) Å, b = 10.573(1) Å, c = 7.415(1) Å, β = 114.846(1)°, and Z = 4. The cationic portion consists of two symmetrical square-planar Pt centers with the inversion center at the midpoint of the Pt(1)∙∙∙Pt(1A) vector. The Pt(II) ion is coordinated by four N atoms from two ammonia molecules and two bridging amido groups affording a slightly distorted square. The molecules are stacked in such a way that the planes of coordination squares turn out to be parallel to each other with a distance of 3.501 Å. Intermolecular Pt–H interaction between the μ-NH₂ hydrogens and the platinum(II) centers of the adjacent molecule are observed.