Synthesis,spectroscopic, structural and thermal characterizations of [(C7H6NO4)2TeBr6·4H2O]

Tellurium (IV) complexes with pyridine-2,6-dicarboxylate ligand were synthesized by slow evaporation from aqueous solutions yielding a new compound: [(C₇H₆NO₄)₂TeBr₆·4H₂O]. The structure of this compound was solved and refined by single-crystal X-ray diffraction. The compound is centrosymmetric P2₁/c (N°: 14) with the parameters a = 8.875(5) Å, b = 15.174(5) Å, c = 10.199(5) Å, β = 94.271° (5) and Z = 2. The structure consists of isolated H₂O, isolated [TeBr₆]^2? octahedral anions and (pyridine-2,6-dicarboxylate) [C₇H₆NO₄]⁺ cations. The stability of the structure was ensured by ionic and hydrogen bonding contacts (N–H?Br and O–H?Br) and Van-Der Walls interaction. The thermal decomposition of the compound was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The FTIR and Raman spectroscopy at different temperatures confirm the existence of vibrational modes that correspond to the organic, inorganic and water molecular groups. Additionally, the UV–Vis diffuse reflectance spectrum was recorded in order to investigate the band gap nature. The measurements show that this compound exhibits a semiconducting behavior with an optical band gap of 2.66 eV.     

The crystal structure of bis(N-pentafluorophenyl)tetraphenyl-cyclodisilazane-tetrabenzene, (Ph2SiNC6F5)2 · 4C6H6

The disilazane (Ph₂SiNC₆F₅)₂ crystallises from benzene solution with four molecules of solvent in the orthorhombic space group Pnna with a 18.182(6), b 21.480(8) and c 13.631(5) Å, Z = 4. The structure was solved by direct methods and refined by least-squares to R 0.069 for 937 observed reflections. The Si₂N₂ ring is planar with NSiN and SiNSi angles of 85.2 and 95.5° respectively; the mean SiN distance is 1.755 Å. The C₆F₅ groups are twisted by ca. 16° from the Si₂N₂ plane and the benzene molecules are arranged face-on above and below each of the C₆F₅ groups. There are, in addition, short intermolecular contacts between four fluorines of each C₆F₅ group and hydrogen atoms from both solvate benzene and the phenyl groups of a symmetry related silazane. Attempts to refine the related (Me₂SiNC₆F₅)₂ structure were not successful, probably due to disorder.     

The Synthesis of the Arene Clusters Ru6C(CO)14(η6-Arene) (Arene = C6H5CHMe2, C6H5C4H9, C6H5C3H7, and C6H5C3H5)

On reaction with Ru₃(CO)₁₂, isopropenylbenzene and 4-phenyl-l-butene undergo hydrogenation, to yield the clusters, Ru₆C(CO)₁₄(⁶-C₆H₅CHMe₂) 1 and Ru₆C(CO)₁₄(⁶-C₆H₅C₄H₉) 2, respectively. With allylbenzene, both hydrogenation and isomerization occurs affording Ru₆C(CO)₁₄(⁶-C₆H₅C₃H₇) 3 and Ru₆C(CO)14(⁶-C₆H₅C₃H₅) 4. The structures of 1 and 2 have been established by single crystal X-ray diffraction. One of the Ru–Ru bond lengths in 2 is unusually long and extended Hückel molecular orbital calculations have been used in an attempt to rationalize this feature.     

New Ruthenium Complexes of Fullerene C60＆C70

The new complexes[Ru(NO)(PPh3)]2(η^2-Cm)(m=60 1 or 70 2)have been prepared by heating a solution of C60(or C70)with[Ru(NO)2(PPh3)2]in toluene.They have been characterized by elemental analysis,IR,UV/VIS,XPS,^13C and ^13P NMR spectroscopy.The photovaltaic effect for the new compounds has been studied.     

Synthesis and Crystal Structure of (C6N3H18)2Ti4O4(C2O4)7·4H2O

The title compound (C6N3H18)2Ti4O4(C2O4)7(4H2O 1 (C13H22N3O18Ti2, Mr = 604.14) was synthesized by the reaction of Ti(SO4)2, H2C2O4(2H2O and N-(2-ammonioethyl)- piperazinium (AEPP) in aqueous solution. The single-crystal X-ray analysis has revealed that 1 crystallizes in the triclinic system, space group Pī with a = 9.1437(6), b = 11.4991(10), c = 11.6975(8)A, α = 96.2915(18), β = 107.998(3), γ = 104.276(4)°, V = 1110.35(14)A3, Z = 2, Dc = 1.807 g/cm3, F(000) = 618, μ = 0.815 mm－1, the final R = 0.0463 and wR = 0.1264 for 3718 observed reflections with I > 2σ(I). X-ray crystal-structure analysis suggests that compound 1 consists of [Ti4O4(C2O4)7]6－ anion and two protonated N-(2-ammonioethyl)piperazinium cations. The anions are linked into an infinite chain through Ti4O4(C2O4)8 by sharing the oxalates as bridging ligands.     

An investigation of the crystalline structure of the quasi-two-dimensional metamagnet of composition [C6H22N4]4+[CuCl4]Cl2 (I), with [C6H22N4]4+=[1,4,7,10-tetraazadecane]·4HC1

[C₆H₂₂N₄]⁴⁺[CuCl₄ ^2–]Cl₂ (I) crystallizes in the monoclinic space groupP2₁/c with cell constantsa=15.573(2) Å,b=7.281(2),c=7.092(2),=91.496(14)°,V= 803.874 ų, andd(z= 2 mol/cell)=1.762 gm cm^–3. Data were collected in the range 4° 2 50°, for a total of 2662 reflections, of which 2201 were independent and hadI 3(I). These were used in the solution and refinement of the structure. TheF(hkl) _obs were corrected for absorption (=23.558 cm^–1) using Psi scan curves of eight suitable reflections, leading to relative transmission coefficient adjustments ranging from 0.9999 to 0.5722. Structural refinement converged atR(F)= 0.023 and R _W (F)=0.026. The coordination around the metal consists of polymeric, axially elongated, six-bonded, trigonal antiprismatic CuCl₆ species, not the hoped for, discrete, molecular CuCl₆ ^4– species implied by their chemical formulation. The crystalline lattice contains three different types of ions: the (C₆H₂₂N₄)⁴⁺ cation, a pair of Cl^– anions which are hydrogen bonded to the secondary ammonium (-NH₂ ⁺-) hydrogens of the cation, and a CuCl₄ ^2– anion. The latter is polymerized into two-dimensional sheets linked to each other by the agency of the cations, in which the two sets of terminal (-NH₃ ⁺) hydrogen bond to the axial Cl^– ligands. The Cu-Cl distances are 2.279, 2.315, and 2.847 Å. The distance between nearest coppers in adjacent sheets is 15.573(2)Å, the length of thea-axis. The magnetic behavior of the compound is that of a metamagnet, which requires a somewhat unusual set of conditions and is very rare in Cu²⁺ compounds. Comparison of the magnetic behavior of (I) with that of related compounds is made. The thermal behavior of (I) was studied using differential scanning calorimetric measurements in the range of 120 K to its melting(dec) point (463 K). It undergoes a phase transition from green (low temperature phase) to golden yellow (room temperature phase) at 168 K, another phase transition (golden yellow to red) at 340.6 K, and another at 383.2 K during which there is not evident color change. Finally, it melts with decomposition at ca. 463 K.     

Synthesis, crystal structure, and thermal analysis of hexahydrogen dodecavanadate of composition [NH3 · H2O]6 · H6[Ca4V12O40] · 6H2O

Dihydrogen dodecavanadate of composition [NH₃ · H₂O]₆ · H₆[Ca₄V₁₂O₄₀] · 6H₂O was synthe-sized and studied by X-ray crystallography and TGA analyses. The crystals are cubic, space group I $\bar 4$ 3m;; unit cell parameters: a = 13.518(2) ?, V = 2470.4(3) ?³, ??_calc = 2.2334 g/cm³, Z = 2.     

Synthesis,crystal structure of Gd(H2O)(C2O4)2 · NH4 and of La(C2O4)2 · NH4. Characterization of the Ln(H2O)(C2O4)2 · NH4 with Ln=Eu…Yb

Single crystals of two lanthanide complexes, presenting similar formula Ln(H₂O)_x(C₂O₄)₂ · NH₄ with Ln=La, x=0 and Ln=Gd, x=1, have been prepared, in closed system at 200 °C. The gadolinium complex is bi-dimensional. A layer is built by the packing of the basic unit, [Gd(C₂O₄)]₄. The gadolinium atoms are related only by bischelating oxalate ligands, the ammonium ion and the water molecule (bound to the gadolinium atom) are localized into the interlayer space. The lanthanum complex is tri-dimensional. The basic building unit remains approximately the same and the packing of these units form a layer. However, within these units, the lanthanum atoms are related by either an oxalate ligand or an edge. Moreover, an oxalate ligand assumes the connection between the layers. The ammonium ion is localized into two sets of intersecting channels. Pure phase of the gadolinium complex has been prepared at 100 °C and extended to some lanthanide elements, Eu…Yb. As the size of the lanthanide ionic radius is decreasing, it is noticeable that the a unit–cell constant follows an expansion pattern while the others two follow an usual contraction one. The thermal behavior of this family shows that the anhydrous compounds are obtained and that some water molecule is sorbed during the cooling. Thus, the anhydrous compounds present a relatively open-framework with some small micropores.     

Spin-density distribution of the high Tcp-O2N·C6F4·CNSSN free radical studied by polarised neutron diffraction

Knowledge of the spin-density distribution in the dithiadiazolyl radical ring (DTDA) constitutes a major step towards the understanding of the magnetic and electronic properties of the rich magnetism of DTDA derivatives. The p-O₂N·C₆F₄·CNSSN radical was chosen as the most favourable CNSSN derivative to study the spin distribution in this kind of free radical by polarised neutron diffraction. Spin-density maps obtained for the p-O₂N·C₆F₄·CNSSN radical show that almost all the spin density is localised on the sulphur and nitrogen atoms of the CNSSN ring. A small negative spin density on the carbon atom of the CNSSN ring and a negligible spin density over the rest of the radical are observed, in good agreement with ab initio calculations.     

FTIR spectra of the 2ν4, ν4 + ν6 and 2ν6 bands of formaldehyde

High resolution IR spectra of the overtones and the combination band of the ν₄ and ν₆ modes of formaldehyde (2ν₄, ν₄ + ν₆ and 2ν₆) were measured in the region of 2200–2650 cm⁻¹ using FTIR. The combination band ν₄ + ν₆, whose dipole transition is forbidden from molecular symmetry, was observed due to the intensity borrowed from the other bands. The observed frequencies were analysed by a Hamiltonian in which A-type Coriolis interactions and Darling—Dennison interaction were taken into account. The ratio and the relative signs of the transition dipole moments of the overtone bands, μ_2ν4 and μ_2ν6, have been determined by analysing the intensity distribution of the vibration—rotation lines.     

Preparation of η2-complexes of fullerenes by reduction. Crystal structure and optical properties of {Ni(dppp)·(η2-C70)}·(C6H4Cl2)0.5

The new reduction method for preparation of η(2)-complexes of fullerenes with nickel-1,3-bis(diphenylphosphino)propane has been developed in which Ni(dppp)Cl(2) and C(60)(C(70)) mixtures are reduced with sodium tetraphenylborate. Single crystals of the first η(2)-complex of nickel with fullerene C(70): {Ni(dppp)·(η(2)-C(70))}·(C(6)H(4)Cl(2))(0.5) (1) (C(6)H(4)Cl(2) = o-dichlorobenzene) have been obtained as well as the previously described complex with fullerene C(60): {Ni(dppp)·(η(2)-C(60))}·(Solvent) (2). The crystal structure of 1 has been solved to show the coordination of nickel to the C-C bond of C(70) at the 6-6 ring junction of η(2)-type to form Ni-C(C(70)) bonds of 1.929-1.941(2) ? length, the shortest M-C bonds among those known for η(2)-complexes of fullerenes C(60) and C(70). The length of the C-C bond to which Ni atom is coordinated (1.494(3) ?) is noticeably longer than the average length of these bonds in C(70) (1.381(2) ?). Optical spectra of 1 in the IR- and UV-visible ranges have been analyzed to show the splitting of some C(70) bands due to C(70) symmetry lowering. The complex has a red-brown color in solution and manifests three bands in the visible range at 379, 467 and 680 nm. The solution of 1 is air sensitive since air exposure restores the color and absorption bands of the starting C(70) at 383 and 474 nm.     

Cooperativity between S···π and Rg···π in the OCS···C6H6···Rg (Rg = He, Ne, Ar, and Kr) van der Waals complexes

The complexes OCS···C(6)H(6), C(6)H(6)···Rg, and OCS···C(6)H(6)···Rg (Rg = He, Ne, Ar, and Kr) have been studied by means of MP2 calculations and QTAIM analyses. The optimized geometries of the title complexes have C(6v) symmetry. The intermolecular interactions in the OCS···C(6)H(6)···Rg complexes are comparatively stronger than that in the OCS···C(6)H(6) complex, which prove that the He, Ne, Ar, and Kr atoms have the ability to form weak bonds with the benzene molecule. In QTAIM studies, the π-electron density of benzene was separated from the total electron density. The molecular graphs and topological parameters of the OCS···πC(6)H(6), πC(6)H(6)···Rg, and OCS···πC(6)H(6)···Rg complexes indicate that the interactions are mainly attributed to the electron density provided by the π-bonding electrons of benzene and the top regions of the S and Rg atoms. Charge transfer is observed from the benzene molecule to SCO/Rg in the formation of the OCS···C(6)H(6), C(6)H(6)···Rg, and OCS···C(6)H(6)···Rg complexes. Molecular electrostatic potential (MEP) analyses suggest that the electrostatic energy plays a pivotal role in these intermolecular interactions.     

室温下甲苯中C6-60和C6-70的电化学检测

采用铂微电极观察到了室温下(25±1)℃甲苯单一溶剂中C60和C70的六步单电子电化学还原过程.在甲苯中采用一般的有机相支持电解质溶解度差,电势窗口也不宽.实验结果表明,离子液体[Tetrahexylammonium bis(trifluoromethylsulfonyl)imide,THA-Tf2N]在甲苯中具有良好的溶解度,因而可以作为这种非极性溶剂的理想支持电解质,并且该体系可以提供宽达-3.7 V(相对于二茂铁电对,Fe /Fe)的电化学还原窗口,这是在室温下实现C6-60和C6-70的电化学检测的主要原因.     

Synthesis and crystal structure of KBi(C6H4O7) · 3.5H2O

A novel compound, KBi(C₆H₄O₇) · 3.5H₂O (I), has been synthesized in the Bi(NO₃)₂-K₃(HCit) system (HCit^3? is an anion of citric acid C₆H₈O₇) at a component ratio (n) of 8 in a water-glycerol mixture, and its crystal structure has been determined. The crystals are unstable in air. The crystals are triclinic: a = 7.462 Å, b = 10.064 Å, c = 17.582 Å, α = 100.27°, β = 99.31°, γ = 105.48°, V = 1221.2 ų, Z = 2, space group $P\bar 1$ . In the structure of I, asymmetric binuclear fragments [Bi₂(Cit^4?)₂(H₂O)₂]^2? are linked through inversion centers into polymeric chain anions. Ions K⁺ and crystal water molecules are arranged in channels between the chains. The Bi(1)...Bi(2) distances in the binuclear fragment are 4.62 Å, and the Bi(1)...Bi(1) and Bi(2)...Bi(2) distances between bismuth atoms in the chain are 5.83 and 5.95 Å, respectively. The chains are linked through bridging oxygen atoms of the ligands Cit to form layers. In the centrosymmetric four-membered chelate ring Bi₂O₂ formed through Bi-O(Cit) bonds, the distances Bi(1)-Bi(1) are equal to 4.55 Å, and Bi(1)-O are 2.66 and 2.84 Å. The Bi-O bond lengths in I are in the range 2.12–3.16 Å. The Cit ligands act as hexadentate chelating/bridging ligands.     

Density, Viscosity, Refractive Index, and Speed of Sound in Binary Mixtures of Pyridine and 1-Alkanols (C6, C7, C8, C10) at 303.15 K

The densities (ρ), viscosities (η), refractive indices (nD), and speeds of sound (u), of binary mixtures of pyridine with 1-hexanol, 1-heptanol, 1-octanol and 1-decanol, including those of pure liquids, were measured over the entire composition range at 303.15 K and atmospheric pressure. From these experimental data, the values of excess molar volumes (VE), deviations in isentropic compressibilities (Δks), viscosities (Δh), molar refractions (ΔRm), apparent and partial molar volumes (Vf,2 and ), apparent and partial molar compressibilities (Kf,2 and ), of alkanols in pyridine and their corresponding deviations (ΔV and ΔK) were calculated. The variations of these parameters with composition of the mixtures suggest that the strength of interactions in these mixtures follow the order: 1-hexanol＞1-heptanol＞1-octanol＞1-decanol. All the excess and deviation functions were fitted to Redlich-Kister polynomial equation to determine the fitting coefficients and the standard deviations.     

Kinetics and mechanism of the dehydration of α-NiSO4·6H2O

A study of the thermal dehydration of α-NiSO₄·6H₂O has been performed by power compensation differential scanning calorimetry in flowing nitrogen. No significant differences in behaviour were observed using either uncrushed crystalline powders or single crystal slabs cleaved parallel to {001}. In good agreement with previous findings, the kinetic analysis of the thermal curves confirms the validity of an=2 Avrami-Erofeev equation (AE2) in isothermal experiments at low (338–343 K) temperatures or in the initial portions of variable temperature runs. The kinetic obedience is however of an ‘order of reaction’ type for the main portion of the variable temperature runs and, for isothermal experiments, in the upper part of the temperature range investigated. Values of activation energies and frequency factors are reported. Parallel studies by optical microscopy showed relevant changes of surface texture when partially (thermally or vacuum) dehydrated {001} cleaved surface were submitted to rehydration. This phenomenon (named orange peel formation) indicates that a dehydrated layer forms on the crystal surfaces preceding the appearance of product crystals (germination or nucleation). Microscopy also revealed that reaction goes on inside the crystal and that product formation takes place in the bulk phase, following lattice collapse in experiments at high heating rates. Combined with previous results, these new experimental findings allow us to formulate a mechanism for the present transformation, comprising three main rate processes:

1. the reaction (detachment of water molecules from their lattice positions in the reactant);
2. the migration of the water molecules freed by the reaction through the initially formed, water-depleted layer enveloping the reactant crystal;
3. the crystallization of such a layer to form the product.

     

C4H6O,C4H6S与XF (X＝F,Cl, Br)分子间卤键的电子密度拓扑研究

运用MP2/aug-cc-pVDZ方法对2,5-二氢呋喃, 2,5-二氢噻吩与XF (X＝F, Cl, Br)之间的卤键作用进行了理论研究. 研究发现: C₄H₆O, C₄H₆S与XF之间不仅存在O(S)…XF n型卤键, C＝C双键与XF分子亦可形成π型卤键|对于C₄H₆O与XF之间的n型和π型卤键以及C₄H₆S与XF之间的π型卤键, 卤键键能ΔE、键鞍点处的电子密度ρ(r_c)以及电子给体到受体之间的电子转移数Δq(XF)均按B…F₂＜B…ClF＜B…BrF (B＝C₄H₆O, C₄H₆S)的顺序依次增大|对于卤键键能较大的体系C₄H₆O…BrF(n), C₄H₆O…BrF(π), C₄H₆S…F₂(n), C₄H₆S…ClF(n), C₄H₆S…BrF(n), C₄H₆S…BrF(π), 卤键作用介于离子键和共价键之间|而对于其它的卤键键能较小的体系, 卤键作用为闭壳层静电作用.     

The mechanism and kinetics of energy transfer processes in the Xe–CCl4–M (M=CH4, C2H2, C2H4, C2H6 C3H6 and C3H8) mixtures irradiated by xenon resonance light

The mechanism and kinetics of energy transfer from Xe(6s[3/2]₁) resonance state (E=8.44 eV) to selected hydrocarbon molecules have been investigated by XeCl(B–X) (λ_max=308 nm) fluorescence intensity measurements at stationary conditions in Xe–CCl₄–M systems. Steady-state analysis of the fluorescence intensity dependence on the xenon and M pressure at constant CCl₄ concentration shows that these process occur in the two- and three-body reactions: Xe(6s[3/2]₁⁰)+M→products, Xe(6s[3/2]₁⁰+M+Xe→products. The two- and three-body rate constants for these reactions have been found (see Table 1Table 1. Experimental parameters of Eq. (8)found by least square method in Xe–CCl₄–C₂H₂ and Xe–CCl₄–C₂H₄ systems for chosen xenon pressures in the range 25–150 Torr. Linear correlation coefficients (R) are also shown