Tautomeric and conformational properties of dibenzoylmethane,C<Subscript>6</Subscript>H<Subscript>5</Subscript>–C(O)–CH<Subscript>2</Subscript>–C(O)–C<Subscript>6</Subscript>H<Subscript>5</Subscript>: gas-phase electron diffraction and quantum chemical study

Tautomeric and structural properties of dibenzoylmethane, C₆H₅–C(O)–CH₂–C(O)–C₆H₅, have been investigated by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximation with different basis sets up to cc-pVTZ). Analysis of GED intensities resulted in the presence of 100(5)% enol tautomer at 380(5) K. The enol ring possesses C _S symmetry with a strongly asymmetric hydrogen bond. The two phenyl rings are rotated with respect to the enol ring by 15.1(5.0) and 12.1(5.8)°. The experimental geometric parameters are reproduced very closely by the B3LYP/cc-pVTZ method.     

Reaction of the [B<Subscript>10</Subscript>H<Subscript>9</Subscript>O<Subscript>2</Subscript>C<Subscript>4</Subscript>H<Subscript>8</Subscript>]<Superscript>–</Superscript> anion with C-nucleophiles

The reactions of 1,4-dioxane-substituted closo-decaborate anion ([B₁₀H₉O₂C₄H₈]^–) with metal acetylenides, diethyl malonate, ethyl acetoacetate, triethyl orthoformate, acetylacetone, and malonodinitrile were studied. The reactions were shown to be accompanied with substituent ring opening and attachment of the corresponding pendant functional group. The obtained compounds were characterized by various physicochemical methods (IR and polynuclear NMR spectroscopy, ESI mass spectrometry).     

Transformations of CO<Subscript>2</Subscript> in Two-Phase Systems C<Subscript>8</Subscript>F<Subscript>18</Subscript>–H<Subscript>2</Subscript>O and C<Subscript>6</Subscript>F<Subscript>6</Subscript>–H<Subscript>2</Subscript>O

The transformation of carbon dioxide in aqueous emulsions of perfluorons in the presence of oxygen in the air results in the formation of a mixture of oxalic acid and a minor set of organic compounds C₄–C₈. The maximum CO₂ consumption occurs in the emulsion with the C₈F₁₈: H₂O vol/vol ratio of 1: 0.42 at pH 2.4; the H₂C₂O₄ yield is 11 mol %.     

Crystal structure of [(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)<Subscript>4</Subscript>P][Ni(B<Subscript>9</Subscript>C<Subscript>2</Subscript>H<Subscript>11</Subscript>)<Subscript>2</Subscript>]·CCl<Subscript>4</Subscript>

A new compound containing the tetraphenylphosphonium cation and the nickel(III) bisdicarbollyl anion, [(C₆H₅)₄P][Ni(B₉C₂H₁₁)₂]·CCl₄, was synthesized and investigated by XRD at room temperature (295 K). Crystal data: C₂₉H₄₂B₁₈PCl₄Ni, M = 816.69, monoclinic, space group P2/c; unit cell parameters a = 13.5873(6) Å, b = 7.1475(2) Å, c = 20.7829(8) Å, β = 94.4595(13)°, V = 2012.2(2) ų, Z = 2, d _calc = 1.348 g/cm³. The structure was solved by direct and Fourier methods and refined by the full-matrix least squares method in an anisotropic (isotropic for H) approximation to the final R ₁ = 0.0466 for 3055 I _hkl ≥ 2σ _I of 23,655 reflections collected and 5618 independent I _hkl (Bruker X8 APEX diffractometer, λMoK _α).     

<Superscript>35</Superscript>Cl NQR for the SbCl<Subscript>3</Subscript> complex with aniline,SbCl<Subscript>3</Subscript>·NH<Subscript>2</Subscript>C<Subscript>6</Subscript>H<Subscript>5</Subscript>

The temperature dependence of the ³⁵Cl NQR frequencies and spin-lattice relaxation times has been investigated for a trigonal-bipyramidal vn complex SbCl₃·NH₂C₆H₅. Thermally activated motion of chlorine atoms (pseudorotation) was not revealed in the complex, in contrast to the vπ complexes of SbCl₃ with related molecular structures. The high potential barrier of pseudorotation in the aniline complex is likely to be due to the unusually high nonequivalence of Sb-Cl chemical bonds.     

Crystal structure and solid–solid phase transition of the complex (C<Subscript>11</Subscript>H<Subscript>18</Subscript>NO)<Subscript>2</Subscript>CuCl<Subscript>4</Subscript>(s)

The complex (C₁₁H₁₈NO)₂CuCl₄(s) was synthesized. Chemical analysis, elemental analysis, and X-ray crystallography were used to characterize the structure and composition of the complex. Low-temperature heat-capacities of the compound were measured by an adiabatic calorimeter in the temperature range from 77 to 400 K. A phase transition of the compound took place in the region of 297–368 K. Experimental molar heat-capacities were fitted to two polynomial equations of heat-capacities as a function of the reduced temperature by least square method. The peak temperature, molar enthalpy, and entropy of phase transition of the compound were calculated to be T _trs = 354.214 ± 0.298 K, Δ_trs H _m = 76.327 ± 0.328 kJ mol⁻¹, and Δ_trs S _m = 51.340 ± 0.164 J K⁻¹ mol⁻¹.     

Iron(III)–salen–H<Subscript>2</Subscript>O<Subscript>2</Subscript> as a peroxidase model: electron transfer reactions with anilines

Abstract  

Iron(III)–salen complexes catalyze the H₂O₂ oxidation of various ring-substituted anilines in MeCN have been studied, and [O=Fe^IV(salen)]^+· is proposed as the active species. Study of the kinetics of the reaction by spectrophotometry shows the emergence of a new peak at 445 nm in the spectrum which corresponds to azobenzene. Further oxidation of azobenzene by H₂O₂ leads to the formation of azoxybenzene. ESI–MS studies also support the formation of these products. The rate constants for the oxidation of meta- and para-substituted anilines were determined from the rate of decay of oxidant as well as the rate of formation of azobenzene, and the reaction follows Michaelis–Menten kinetics. The rate data show a linear relationship with the Hammett σ constants and yield a ρ value of −1.1 to −2.4 for substituent variation in the anilines. A reaction mechanism involving electron transfer from aniline to [O=Fe(salen)]^+· is proposed. The presence of axial ligands modulates the activity of the complex.     

Synthesis,crystal structure and DNA-binding studies of the complex [Co(C<Subscript>10</Subscript>H<Subscript>9</Subscript>N<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>] · 3H<Subscript>2</Subscript>O

A novel binuclear Cobalt(II) complex with N-(2-propionic acid)-salicyloyl hydrazone (C₁₀H₁₀N₂O₄, H₃L) was prepared and characterized. The crystal structure of [Co(C₁₀H₉N₂O₄)₂] · 3H₂O was determined by X-ray single-crystal diffractometry. The Co²⁺ ion is six-coordinated by the carboxyl and acyl O atoms and azomethine N atoms of two tridentate N-(2-propionicacid)-salicyloyl hydrazone ligands, which form two stable five-numbered rings sharing one side in the keto form. The coordination environment around the Co²⁺ ion might be described as a distorted octahedron. Abundant hydrogen bonds of the types O-H…N and O-H…O between the water molecules and ligands not only form the three-dimensional network, but also provide an extrastability for the crystal. The complex was studied for the interaction with calf thymus DNA by electronic absorption titration and emission titration. The results show that the complex is bound to calf thymus DNA mainly by intercalation. The article is published in the original.     

Phase and extraction equilibria in H<Subscript>2</Subscript>O–sulfonol–HCl (H<Subscript>2</Subscript>SO<Subscript>4</Subscript>) and H<Subscript>2</Subscript>O–sodium dodecyl sulfate–HCl (H<Subscript>2</Subscript>SO<Subscript>4</Subscript>) systems

Solubility isotherms of water–sulfonol–hydrochloric (or sulfuric) acid and water–sodium dodecyl sulfate–hydrochloric acid systems at 75°C and a water–sodium dodecyl sulfate–sulfuric acid system at 50°C are constructed. Regions of two-phase liquid equilibrium suitable for use in extraction are found. Concentration parameters for extraction are determined. The interfacial distribution of a series of metal ions with and without such additional complexing reagents as diantipyrylmethane and diantipyrylheptane is studied.     

Interaction of [В<Subscript>10</Subscript>H<Subscript>10</Subscript>]<Superscript>2–</Superscript> and [В<Subscript>12</Subscript>H<Subscript>12</Subscript>]<Superscript>2–</Superscript> with nitro compounds

The interaction of the [B₁₀H₁₀]^2– and [B₁₂H₁₂]^2– anions with aliphatic and aromatic nitro compounds (RNO₂, where R = Et, n-Pr, i-Pr, tert-Bu, Ph) has been studied under irradiation with visible and UV light. It has been shown that, depending on the reaction conditions, both mono- and disubstituted nitro-closo-decaborates can be selectively obtained in yields up to 50%.     

The undecahydrodecaborate anion B<Subscript>10</Subscript>H<Stack><Subscript>11</Subscript><Superscript>−</Superscript></Stack> as the starting reagent in exopolyhedral substitution and complexation: Theoretical and experimental prerequisites

Using the electron density functional theory (B3LYP approximation) with the 6-31G* basis set, the potential energy surface of the undecahydrodecaborate anion B₁₀H₁₁⁻ was calculated and the activation energies and the activation barriers for the elementary reactions of proton H* migration around the boron polyhedron were estimated. Analysis of the calculation results in comparison with the experimental data accumulated recently implies that the salts of the B₁₀H₁₁⁻ anion represent a new type of starting compounds for exopolyhedral substitution and complexation involving decaborate anions. Of particular interest is the targeted preparation of isomers of metal complexes containing a decaborate anion depending on the use of B₁₀H₁₀²⁻ or B₁₀H₁₁^¨- as the starting reagent. Certain trends in the reactivity of B₁₀H₁₀⁻ and B₁₀H₁₁⁻ anions can be explained in terms of the simple analysis of Mulliken charge distribution on atoms.     

Synthesis and Crystal Structure of [Co(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>](C<Subscript>19</Subscript>H<Subscript>17</Subscript>O<Subscript>4</Subscript>SO<Subscript>3</Subscript>)<Subscript>2</Subscript>⋅8H<Subscript>2</Subscript>O

The title compound, cobalt 4′,7-diethoxylisoflavone-3′-sulfonate([Co(H₂O)₆](X)₂⋅8H₂O, X = C₁₉H₁₇O₄SO₃) was synthesized and its structure was determined by single-crystal X-ray diffraction analysis. It crystallizes in the triclinic space group P-1 with cell parameters a = 9.026(3) Å, b = 16.431(5) Å, c = 18.195(6) Å, α = 72.289(4)^∘, β = 87.498(4)^∘, γ = 82.775(5)^∘, V = 2550.1(13) Å⁻³, D_c = 1.419 Mg m⁻³, and Z = 2. The results show that the title compound consists of one cobalt cation, six coordinated water molecules, eight lattice water molecules, and two 4′,7-diethoxylisoflavone-3′-sulfonate anions, C₁₉H₁₇O₄SO⁻₃. Two anions have different conformations. Twelve H atoms of six coordinated water molecules, as donors, form hydrogen bonds with four oxygen atoms of sulfo-groups of two anions and eight oxygen atoms of eight lattice water molecules. In addition, π < eqid1 > ⋅ < eqid2 > π stacking interactions exist in the crystal structure, which together with hydrogen bonds lead to supramolecular formation with a three-dimensional network.     

The ESCA analysis of the B<Subscript>3</Subscript>H<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack> anion

Compounds [Et₄N]₂B₃H₈ and CsB₃H₈ are studied using the ESCA method. The results of analysis of the B1s electron spectra and estimation of the effective charge differences in [Et₄N]₂B₃H₈ are compared to the data of theoretical calculations of the B₃H₈⁻ anion.     

Synthesis and crystal structure of the silver nitrate complex with 4,4′-trimethylenedipiperidine [Ag(C<Subscript>13</Subscript>H<Subscript>26</Subscript>N<Subscript>2</Subscript>)]NO<Subscript>3</Subscript>

A new coordination compound [AgNO₃(C₁₃H₂₆N₂)] was synthesized and structurally characterized. The crystals are triclinic: space group P \(\bar 1\), a = 6.157(1) Å, b = 10.074(1) Å, c = 14.153(1) Å, α = 102.36(1)°, β = 92.16(1)°, γ = 107.33(1)°, V = 813.7(2) ų, ρ_calcd = 1.552 g/cm³, Z = 2. The structure contains centrosymmetric rings formed by two Ag⁺ ions and two bridging trimethylenedipiperidine ligands. The coordination of Ag⁺ ions is close to linear (Ag(1)-N(1), 2.192(5) Å; Ag(1)-N(2), 2.212(5) Å; angle N(1)Ag(1)N(2), 162.7(2)°). Anions NO ₃ ^? form weak bonds with silver ions (Ag(1)…O(1), 2.783(5) Å; Ag(1)-O(3), 2.893(5) Å) and combine rings into supramolecular bands running in the diagonal direction of the unit cell.     

π-Complex of Cu(I) Chloride with 1-Allyloxybenzotriazole CuCl · C<Subscript>6</Subscript>H<Subscript>4</Subscript>N<Subscript>3</Subscript>(OC<Subscript>3</Subscript>H<Subscript>5</Subscript>)

Single crystals of CuCl · C₆H₄N₃(OC₃H₅)(I) are synthesized by ac electrochemical method from Cu(II) chloride and 1-allyloxybenzotriazole in ethanol solution and their unit cell parameters are determined: space group P2₁/a a=11.583(4) , b=11.443(7) , c=8.620(4) , =108.77(3)°, V=1082(2) ³, R(F)=0.0366, R _w (F)=0.0396 for 1095 reflections. In the structure of -complex I, inorganic fragment Cu₂Cl₂ forms centrocymmetric parallelogram. A molecule of 1-allyloxybenzotriazole acts as a bridge, which is bonded to the Cu atoms of two inorganic dimers through the C=C bond of the allyl group and to the N atom of a triazole ring. Owing to this bridging function, the ligand molecules form zigzag organometallic layers. The trigonal-pyramidal coordination sphere of a metal atom includes two Cl atoms and the C=C group. The structural motif of complex I significantly differs from that of the previously studied 2CuCl · C₆H₄N₃(OC₃H₅) and resembles the motif of a bromide analog Cu₂Br₂ · [C₆H₄N₃(OC₃H₅)]₂.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 364–369.Original Russian Text Copyright © 2005 by Goreshnik, Myskiv.     

Synthesis and X-ray diffraction study of Li(H<Subscript>3</Subscript>O)[UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)] · H<Subscript>2</Subscript>O

Single crystals of Li(H₃O)[UO₂(C₂O₄)₂(H₂O)] · H₂O (I) have been synthesized and studied by X-ray diffraction. Compound I crystallizes in the monoclinic crystal system with the unit cell parameters: a = 7.1682(10) Å, b = 29.639(6) Å, c = 6.6770(12) Å, β= 112.3(7)°, space group P 2₁/c, Z = 4, R = 4.36%. Structure I contains discrete mononuclear groups [UO₂(C₂O₄)₂(H₂O)]^2? ascribed to the crystal-chemical group AB ₂ ⁰¹ M¹ (A = UO₂ ²⁺, B⁰¹ =C₂O ₄ ^2? , M¹ = H₂O), which are “cross-linked” by the lithium ions into infinite layers {Li(UO₂)(C₂O₄)₂(H₂O)₂}^? perpendicular to [010]. The hydroxonium ions are located between adjacent uranium-containing layers. A hydrogen bond system involving water molecules, oxalate ions, and hydroxonium combines the anionic layers into a three-dimensional framework.     

Synthesis and crystal structure of complex [Mn(Imdc)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · 2H<Subscript>2</Subscript>O and its interaction with DNA

Under hydrothermal conditions, the complex [Mn(lmdc)₂(H₂O)₂] · 2H₂O (I) was synthesized and characterized by elemental analysis and IR spectrum (HImdc = 4,5-imidazofedicarboxylic acid). The crystal structure of I was determined by single-crystal X-ray diffraction (crystallizing in the monoclinic crystal system, P ₂/c space group, a = 11.000(2), b = 7.1281(14), c = 12.696(3) Å, β = 122.45(3), Z = 2. In I, the Mn²⁺ ion was chelated by two Imdc with one of their nitrogen atoms and a carboxylic oxygen atom, while two water molecules occupy the axial position of the Mn atom forming a distorted octahedral geometry. Three-dimensional structure of I was formed by intermolecular hydrogen bonds. UV-Vis and fluorescence spectra of I interacting with DNA show that insertion is the main binding mode between I and fish sperm DNA. Gel electrophoresis shows that I cleaves both supercoiled and circular pBR322 DNA to form a small molecular fragment.     

Phase equilibria in a ternary fullerenol-d(C<Subscript>60</Subscript>(OH)<Subscript>22–24</Subscript>)–SmCl<Subscript>3</Subscript>–H<Subscript>2</Subscript>O system at 25°C

The solubility in a ternary fullerenol-d (C₆₀(OH)_22–24)–SmCl₃–H₂O system at 25°C is studied via isothermal saturation in ampules. The solubility diagram is shown to be a simple eutonic one that consists of two branches corresponding to the crystallization of fullerenol-d (C₆₀(OH)_22–24 · 30H₂O) and samarium(III) chloride SmCl₃ · 6H₂O crystallohydrates and contains one nonvariant eutonic point corresponding to saturation with both crystallohydrates. The long branch of C₆₀(OH)_22–24 · 30H₂O crystallization shows the effect of fullerenol-d salting out of saturated solutions; in contrast, the short branch of SmCl₃ · 6H₂O crystallization shows the pronounced salting-in effect of samarium(III) chloride.     

Intercalation and controlled release of vitamin B<Subscript>6</Subscript> from montmorillonite–vitamin B<Subscript>6</Subscript> hybrid

Controlled release of a therapeutic agent to patients is gaining enormous importance during the recent past. The present paper focused on the intercalation of vitamin B₆ (pyridoxine, VB₆) into montmorillonite (MMT) as a controlled release drug carrier. MMT used in this study is of Indian origin. Intercalation of VB₆ into MMT at different times, temperatures, pH values, and initial concentration is illustrated. The MMT–VB₆ hybrid was characterized by X-ray diffraction, Fourier transform infrared, and thermogravimetric analysis. VB₆ was successfully adsorbed on the surface of MMT and also intercalated into the interlayer of MMT. The release processes were monitored under in vitro conditions using simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 7.4) at 37 ± 0.5 °C. In vitro release experiments revealed that VB₆ was released from the MMT–VB₆ hybrid steadily and was pH-dependent.     

The solubility of fullerene C<Subscript>60</Subscript>-fullerene C<Subscript>70</Subscript> mixtures in styrene at 25°C

The solubility of fullerene C₆₀-fullerene C₇₀ mixtures in styrene was studied under isothermal conditions at 25°C. The corresponding solubility isotherm is given and characterized.