Effects of the substituents Y in reactions of compounds of the type (Me3Si)3CSiH(C6H4Y-p)I. Evidence against the SN2(intermediate) mechanism for methanolysis of (Me3Si)3CSiMe2I and (Me3Si)3CSiHPhI

The rates of methanolysis of the iodides TsiSiH(C₆H₄Y-p)I (Y  MeO, Me, H, Cl, or CF₃) in 1/1 v/v MeOH/dioxane have been shown to be increased by electron withdrawal by Y and correspondingly decreased by electron release. This is taken to imply that the methanol is covalently involved in the transition state, and thus that, contrary to an earlier suggestion, the reaction cannot have an S_N2(intermediate) mechanism. No explanation can at present be offered for the fact that methanolysis of TsiSiHPhI (like that of TsiSiMe₂X with X  I, OClO₃, or OSO₂CF₃) is not accelerated by NaOMe whereas that of some other TsiSiHPhX compounds (e.g. X  Br, ONO₂, or OSO₂Me) is so accelerated, with its implications of a duality of mechanism within an S_N2 range. The reactions of the iodides TsiSiH(C₆H₄Y-p)I with KSCN in MeCN are also accelerated by electron withdrawal by Y, whereas those with AgOAc in MeCO₂H are accelerated by electron release.     

Internal dynamics of the LaI3 molecule. II. Thermal average structure of the molecule and mean square vibration amplitudes

The structural parameters of the effective r _g configuration of the LaI₃ molecule were calculated using the DFT/B3LYP method. The difference between the calculated values of r _e (La-I) and r _g (La-I) is mostly due to the anharmonicity of the ν₁ and ν₂ vibrations and does not exceed the error in determining the distance r _g (La-I) in the electron diffraction experiment. Inclusion of the anharmonicity of the ν₂ and ν₄ deformation vibrations in calculations leads to decreased amplitudes l(I…I) and shrinking effect δ(I…I) compared to the respective values obtained in the harmonic approximation. The LaI₃ molecule proved to be more rigid than predicted by B3LYP calculations.     

Relative concentrations and relaxation properties of isomeric alkyl radicals in γ-irradiated n-alkane single crystals

The relative concentrations of alkyl radicals CH₃C?HCH₂R(I) and R'CH₂C?HCH₂R''(II) were measured at low microwave power in some n-alkane single crystals γ-irradiated at 77 K to a dose of 1 Mrad. The relative concentration of radical (II) increased as the number of carbon atoms became larger. The amount of radical (I) was in agreement with a mechanism where all CH bonds in an n-alkane molecule are raptured with the same probability followed by an isomerization of primary alkyl radicals to radical (I). In n-decane for instance this mechanism predicts 45.5% of radical (I) compared to the experimental value of 45.5%. Saturation measurements of radical (I) and radical (II) under slow passage condition showed that the spin-lattice relaxation time T₁ is shorter for radical (I) (ca. 3 × 10^?4s) than for radical (II) (ca. 80 × 10^?4s), while the spin-spin relaxation times T₂ are similar (ca. 2 × 10^?8s). The relatively short relaxation time T₁ in radical (I) is thought to originate from higher mobility of the end of the alkane chain, where the unpaired electron is localized, and also a modulation of the hyperfine coupling from protons in the nearby rotating methyl group. The broad linewidth in irradiated protiated cyrstals was by comparison with results from deuterated matrices concluded to depend on slightly distorted radicals in damaged regions (spurs, short tracks, blobs) and not on electron dipole-dipole interactions. Unresolved γ-proton couplings in radical (I) are thought to cause the spin-flip transitions at high microwave power.     

Measured Stark widths and shifts of the neutral argon spectral lines in 4s–4p and 4s–4p′ transitions

We investigate the Stark widths (W) and the shift (d), of the seven neutral argon (Ar I) spectral lines from the 4s–4p and 4s–4p′ transitions. The line shapes are measured in a linear, low-pressure, optically thin pulsed arc discharge at about 16 000 K electron temperature (T) and about 7.0 × 10²² m^− 3 electron density (N). The new data separates the electron width (W_e) and ion width W_i from the total Stark width (W_t), as well the separation of electron total Stark shift (d_t) on electron (d_e) and ion (d_i) parts. There are no theoretical predictions for these lines. Comparison to theoretical predictions for other lines within the same multiplets finds that the experimental data exhibits stronger influence by the ion contribution to the measured Ar I line shape. We have also deduced the ion broadening parameters which describe the influence of the ion static (A) and the ion–dynamical (D and E) effect on the width and the shift of the line shape.Applying the line deconvolution procedure, the basic plasma parameters i.e. electron temperature (T) and electron density (N) are recovered. The plasma parameters (T and N) are measured using independent diagnostics techniques as well. Good agreement is found among two sets of the N and T plasma parameters obtained from deconvolution procedure and independent diagnostics techniques.     

Cross sections and spin polarizations of electrons elastically scattered from oriented molecules (CH3I)

Elastic differential cross sections and spin polarizations for electrons elastically scattered from CH₃I are calculated using the independent atom model. Three molecular orientations with respect to the incident electron wavevector are considered — first, the molecule is oriented randomly, second, the electron wave front and molecular bond are parallel, and third, the wavefront and the bond axis are perpendicular. It will be seen to what extent orientational averaging weakens features of the cross section and spin polarization. The calculations show that cross section and spin polarization measurements are a possible tool for determining the degree of molecular orientation. There is no degeneracy betweenI–C andC–I in cross section and spin polarization measurements. The results presented here for 200 eV and 600 eV electrons scattered by CH₃I should be considered as a case study and it should be possible to find molecules and electron energies for which even more dramatic differences between the various orientations between the molecules and the electrons can be expected.     

Hybrid DFT study of electronic structure on quasi-one-dimensional halogen-bridged binuclear metal complexes (MMX)

The electronic structure of quasi-one-dimensional halogen-bridged binuclear metal complex Ni₂(dta)₄I (dta=CH₃CS₂⁻) was investigated by hybrid density functional theory. UB3LYP was successfully applied to reproduce averaged-valence spin density wave state. The magnetic interactions between Ni dimers were estimated by calculating effective exchange integrals (J_ab) using Ni₂(dta)₄I dimer and tetramer models. Calculated J values were consistent with that of experimental results. The natural orbital analysis of the broken-symmetry UB3LYP solution were performed to elucidate symmetry-adapted molecular orbitals and their occupation numbers. Several chemical indices such as polyradical character and information entropy were introduced on the basis of the occupation numbers to discuss the bonding character of MMX chain. All these indices supports that Ni₂(dta)₄I was in the strongly correlating electron system.     

Geometrical and electronic structure of LaI3 molecule from the gas electron diffraction data and quantum chemical calculations

The saturated vapor over LaI₃ has been studied using the electron diffraction method with mass-spectral monitoring. It was determined that at a temperature 1142(10) K, along with monomer molecules, dimers are present in the vapor in the quantity of 0.7 mol.%. Effective configuration parameters of LaI₃ molecule were obtained: r _g(La-I) 2.961(6) Å, ∠_g(I-La-I) 116.5(9)°, l(La-I) 0.106(1) Å and l(I…I) 0.412(7) Å. A small deviation of the valence angle ∠_g(I-L-I) from 120° can be totally caused by a contraction effect of the distance r _g(I…I) of LaI₃ molecule with planar equilibrium configuration. The electronic structure of LaI₃ molecule was examined by the B3LYP/SDD method. In terms of the NBO-analysis, the participation of lanthanum 4f-AO in bonding orbitals La-I is noted. It is shown that the NBO-analysis describes the bond La-I in LaI₃ molecule as predominantly ionic one with a noticeable covalence component. The energy of the heterolytic bond breakage E(La-I)_het = 1216 kJ/mole was calculated.     

Cyclische diazastannylene: XXII. Zur umsetzung eines bis(amino)stannylens mit organylphosphanen, -methylen-phosphoranen, -phosphaniminen, -oxiden und -sulfiden

1,3-Di-t-butyl-2,2-dimethyl-1,3,2,4λ²-diazasilastannetidin (I) was allowed to react with the phosphanes PEt₃ and PPh₃ as well as with Me₃PCH₂, Ph₃PCH₂, Ph₃PNH, Me₃PO and Et₃PS. While the phosphor ylides and the phosphane oxide interact with I to yield crystalline acid-base adducts, no stable adducts can be isolated with the phosphanes and the phosphane sulfide. The adduct of Ph₃PCH₂ and I crystallizes with one benzene molecule per formula unit in the monoclinic space group P2₁/c (a 1188.2(8), b 1438.4(2), c 2169.4(5) pm, β 106.5(4)°). I and Ph₃PCH₂ are linked together by a SnC bond of 240.3(10) pm. The electron transfer from the ylide-carbon to the tin atom can be evaluated from the PC bond length of 174.3(11) pm. The phosphaneimine reacts with I by displacement of the tin atom in I by hydrogen atoms yielding N, N ′-di-t-butyl-Si, Si-dimethylsilazanean and Sn(NPPh₃)₄, and oxidation at the tin atom. 3 molecules of benzene are crystallizing together with one formula unit of Sn(NPPh₃)₄ (monoclinic; C2/c; a 2470.0(4), b 1643.6(6), c 2382.7(4) pm, β 128.1(3)°). The tin atom is the centre of a tetrahedron of nitrogen atoms, the mean SnN-bond length (197.5 pm) being the shortest so far reported.     

The synthesis of ZnS hollow nanospheres with nanoporous shell

ZnS hollow nanospheres with nanoporous shell were successfully synthesized through the evolvement of ZnO nanospheres which were synthesized by hydrothermal method with poly (sodium-p-styrene sulfonate) (PSS) as surfactant at low temperature. The as-synthesized samples were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), UV/vis spectrum and N₂ adsorption. The results showed that the shell of as-synthesized ZnS hollow structure was composed of many fine crystallites and had a nanoporous structure with pore diameter about 4 nm demonstrated by N₂ adsorption/desorption isotherm. The sample possessed efficiency of photocatalytic degradation on X-containing (X=Cl, Br, I) organic pollutants.     

The concentration of surface VO species on oxidized vanadium oxide catalysts

The hollandite-type phase K_1.33Mg_3.11Sb_4.89O₁₆ has been studied by X-ray and electron diffraction as well as high resolution electron microscopy at 500 kV. This material was found to adopt the tetragonal hollandite structure, space group $\text{I4}\text{m}$, with a = 10.315 (4)Å; c = 3.080 (4) Å. The formation of a 3c body-centered supercell was observed and this was shown to be due to ordering of potassium cations within the tunnel sites. Computer image simulations established that ordering of the tunnel cations alone rather than the octahedrally coordinated framework cations was responsible for superlattice formation. In some crystals the supercell ordering appeared to occur in domains.     

Synthesis and equilibrium binding studies of cationic, two-coordinate gold(I) π-alkyne complexes

Reaction of a 1:1 mixture of (L)AuCl [L = P(t-Bu)₂o-biphenyl or IPr] and AgSbF₆ with internal alkynes led to isolation of the corresponding cationic, two-coordinate gold π-alkyne complexes in ≥ 90% yield. Equilibrium binding studies show that the binding affinities of alkynes to gold(I) are strongly affected by the electron density of the alkyne and to a lesser extent on the steric bulk of the alkyne. These substituent effects on alkyne binding affinity are greater than are the differences between the inherent binding affinities of alkynes and alkenes to gold(I).     

Mössbauer studies on ferrocene complexes: XI. Stabilisation and electron transfer in diferrocenyl monocations and related species

The structures of the diferrocenyl methyl cation (I) and protonated diferrocenyl ketone (II) are discussed in terms of modes of stabilisation. Evidence supporting the involvement of e₁ rather than e₂ orbitals in I is given with particular reference to values of Mössbauer quadrupole splittings (QS) which are very much smaller than those of monoferrocenyl carbenium ions. The reaction of Fc₂CO and Fc₂CHOH with FeCl₃ was investigated using frozen solutions. For Fc₂CO, a redox reaction occurred resulting in the oxidation of only one iron site even with excess oxidant. These results were confirmed by cyclic voltammetry. For Fc₂CHOH, no redox reaction was observed but the FeCl₃ appears to coordinate to the alcoholic oxygen atom resulting in a marked diminution of QS. The observed QS values are rationalised in terms of electron donation by the ferrocenyl e₁ orbitals. This explanation is extended to cover previously reported Mössbauer spectra for biferrocenium and biferrocenylenium monocations.     

Two Novel Compounds Built Up of Decavanadate Clusters and Transition-Metal Complexes: Synthesis and Structure

Two inorganic compounds entitled tetrasodium hexaaquacobalt decavanadate tetraco-sahydrate,(I), and diammonium bis[hexaaquamanganese] decavanadate tetrahydrate,(II), have been isolated by conventional solution method and structurally characterized by single-crystal X-ray diffraction methods, scanning electron microscopy, IR spectra, thermal analyses and cyclic voltammetry measurements. They crystallize with triclinic (P-1) symmetry and consists of a centrosymmetric [V₁₀O₂₈]^6? anion. The Co²⁺ and Mn²⁺ cations in (I) and (II) respectively are octahedrally coordinated by six water molecules. Compound (I) also contains a polymeric linear array of edge-sharing [Na(OH₂)₆]⁺ and [Co(OH2)₆]²⁺ octahedra and compound (II) exhibit a catenary structure consisting of [V₁₀O₂₈]^6? anions linked to [Mn(OH2)₆]²⁺ and NH₄ ⁺via hydrogen bonds.     

Spectroscopic studies on the interaction of cimetidine drug with biologically significant σ- and π-acceptors

Spectroscopic studies revealed that the interaction of cimetidine drug with electron acceptors iodine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) resulted through the initial formation of ionic intermediate to charge transfer (CT) complex. The CT-complexes of the interactions have been characterized using UV–vis, ¹H NMR, FT-IR and GC–MS techniques. The formation of triiodide ion, I₃^?, is further confirmed by the observation of the characteristic bands in the far IR spectrum for non-linear I₃^? ion with C_s symmetry at 156 and 131 cm^?1 assigned to ν_as(I–I) and ν_s(I–I) of the I–I bond and at 73 cm^?1 due to bending δ(I₃^?). The rate of formation of the CT-complexes has been measured and discussed as a function of relative permittivity of solvent and temperature. The influence of relative permittivity of the medium on the rate indicated that the intermediate is more polar than the reactants and this observation was further supported by spectral studies. Based on the spectroscopic results plausible mechanisms for the interaction of the drug with the chosen acceptors were proposed and discussed and the point of attachment of the multifunctional cimetidine drug with these acceptors during the formation of CT-complex has been established.     

Facile Microwave Approach for Synthesis of Copper–Indium Sulfide Nanoparticles and Study of Their Behavior in Solar Cell

CuInS₂ (CIS) nanoparticles (nps) were synthesized via a microwave approach by adding eight sulfur sources with a new copper precursor, [bis(acetylacetonato)copper(II)]; [Cu(acac)₂]. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible and photoluminescence spectroscopy. Band gap of as-synthesized nps was 2.1 eV that showed about 0.55 eV blue shift in comparison to its bulk type. As observed in other semiconductor systems, the optical absorption blue shift is associated with quantum confinement effects. Thin film of CIS was prepared by doctor’s blade technique and solar cell made from indium transparent oxide/CIS/CdS/Pt layers. I–V characterization was investigated for this cell and fill factor, open-circuit voltage (V _oc) and short-circuit current (I _sc) were achieved.     

Cationic polymerization of isobutylene with H2O/TiCl4 initiating system in the presence of electron pair donors

Cationic polymerization of isobutylene (IB) in a mixture of methylene dichloride (CH₂Cl₂) and n-hexane (n-Hex) was conducted by using H₂O as initiator, TiCl₄ as co-initiator in the presence of strong external electron pair donor (ED), such as pyridine (Py), dimethylacetamide (DMA) or triethylamine (TEA). The effects of ED concentration, TiCl₄ concentration, solvent polarity, polymerization temperature (T) and time on IB polymerization, molecular weight (MW) and molecular weight distribution (MWD, M_w/M_n) of polyisobutylene (PIB) products were investigated. The relative amount of polymer formed via uncontrolled initiation by conventional active species (I) decreased with increasing the solvent polarity, TiCl₄ concentration and ED concentration in the polymerization. The desirable polymerization of IB with apparent absence of chain transfer reactions could be obtained by H₂O/TiCl₄ initiating system in the presence of ED under the appropriate reaction conditions. The external electron pair donors and TiCl₄ did specially play important and effective roles on polymerization.     

On the nature of spin- and orbital-resolved Cu+–NO charge transfer in the gas phase and at Cu(I) sites in zeolites

Electronic factors essential for NO activation by Cu(I) sites in zeolites are investigated within spin-resolved analysis of electron transfer channels (natural orbitals for chemical valence). NOCV analysis is performed for three DFT-optimized models of Cu(I)?CNO site in ZSM-5: [CuNO]⁺, (T1)CuNO, and (M7)CuNO. NO as a non-innocent, open-shell ligand reveals significant differences between independent deformation density components for ?? and ?? spins. Four distinct components are identified: (i) unpaired electron donation from NO ??_??* antibonding orbital to Cu_s,d; (ii) backdonation from copper d _yz to ??_??* antibonding orbital; (iii) donation from occupied ??_?? and Cu d _xz to bonding region, and (iv) donation from nitrogen lone-pair to Cu_s,d. Channel (i), corresponding to one-electron bond, shows-up solely for spin majority and is effective only in the interaction of NO with naked Cu⁺. Channel (ii) dominates for models b and c: it strongly activates NO bond by populating antibonding ??* orbital and weakens the N?CO bond in contrast to channel (i), depopulating the antibonding orbital and strengthening N?CO bond. This picture perfectly agrees with IR experiment: interaction with naked Cu⁺ imposes small blue-shift of NO stretching frequency while it becomes strongly red-shifted for Cu(I) site in ZSM-5 due to enhanced backdonation.     

The partial hydrogenation of small unsaturated molecules by osmium cluster compounds. The reaction of diispropylcarbodiimide with H2Os3(CO)10

The products (μ-H)[μ-η²-(CH₃)₂CHNHCNCH(CH₃)₂]Os₃(CO)₁₀, I, and (μ-H)- [μ-η²-(CH₃)₂CHNHCO]Os₃(CO)₉[CNCH(CH₃)₂], II have been obtained from the reaction of H₂Os₃(CO)₁₀ with diisopropylcarbodiimine. Both products have been investigated by infrared and ¹H NMR spectroscopies, and by single crystal X-ray diffraction analyses. For I: Space group, P2₁/c, a12.840(4), b  15.724(4), c 12.638(4) Å, β 106.91(2)°, V  2441(2) ų, Z4, ? calc  2.66 g/cc. For 2869 reflections, R  0.051 and R_w  0.052. I contains an N-hydrido, N-isopropylamidinyl ligand bridging one edge of a triangular cluster of three osmium atoms. It was apparently formed by the incorporation of one carbodiimide molecule into the coordination sphere of the cluster followed by the transfer of one hydride ligand to one of the nitrogen atoms. For II: Space group P2 ₁/n;a  13.936(7), b  12.146(2), c  15.509(6) Å, β  105.20(4)°, V  2533(3) Å, Z  4, ?calc  2.57 g/cc. For 3065 reflections, R  0.052 and R_w  0.057. II contains an N-hydrido, N-isopropylformamido ligand bridging one edge of a triangular cluster of three osmium atoms and an isopropylisocyanide ligand. The molecule appears to have been formed by the cleavage of an NCH(CH₃)₂ moeity from one carbodiimide molecule and the transfer of it together with one hydride ligand to the carbon atom of a carbonyl group. The resultant formamido ligand bridges an edge of the cluster. The remaining fragment of the carbodiimide molecule bonds to one of the metal atoms of the cluster as a terminal isocyanide ligand. When heated, I loses one mole of carbon monoxide and forms the new cluster complex (μ-H)[μ₃-η²-(CH₃)₂CHNHCNCH-(CH₃)₂]Os₃(CO)₉ III. On the basis of electron counting schemes, III is believed to contain a triply-bridging amidinyl ligand serving as a five electron donor. Most importantly, no II was formed from I indicating that it is not a precursor -to II. A mechanism for the formation of I and II is presented and discussed.     

A New Copper(I) Coordination Polymer with N2-Donor Schiff Base and Its Use as Precursor for CuO Nanoparticle: Spectroscopic,Thermal and Structural Studies

A new copper(I) coordination polymer, [Cu((3,4-MeO-ba)₂bn)I]_n (1), using a bridging Schiff base ligand, N,N′-bis(3,4-dimethoxybenzylidene)butane-1,4-diamine, (3,4-MeO-ba)₂bn, containing a flexible spacer (=N–CH₂–CH₂–CH₂–CH₂–N=) has been synthesized and characterized by elemental analyses (CHN) and FTIR spectroscopy, thermal analysis and powder X-ray structure analysis. In 1, Cu(I) ions are bridged by Schiff base ligands and iodine atoms forming 1D-chain. The thermal stability of 1 was studied by thermal gravimetric and differential thermal analyses. 1 is used to prepare CuO nanoparticles via solid state thermal decomposition in air and nanoparticles thus formed are characterized by scanning electron microscopy, transmission electron microscopy and powder X-ray diffraction techniques.     

Study on selective separation of cesium from high level liquid waste using a macroporous silica-based supramolecular recognition absorbent

A macroporous silica-based supramolecular recognition absorbent (Calix[4]?+?Dodecanol)/SiO₂?CP, was prepared by successive impregnation and fixing the 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix[4]arene (Calix[4]arene-R14) and its molecule modifier 1-Dodecanol onto SiO₂ silica-based polymer support. The characterization of (Calix[4]?+?Dodecanol)/SiO₂?CP was examined by thermal gravimetry and differential thermal analysis and electron probe microanalysis. Relatively large separation factors of Cs and other metal ions (?? _Cs/M ⁿ⁺ ) above 60 were obtained in the presence of 3?M HNO₃. The adsorption data of Cs(I) fitted well with Langmuir isotherm and the maximum adsorption capacity was estimated to be 0.19?mmol?g^?1. The Cs(I) in 3?M HNO₃ were also effectively adsorption on (Calix[4]?+?Dodecanol)/SiO₂?CP in the column operation, and the loaded Cs(I) was successfully eluted with an eluent of H₂O. The column packed with (Calix[4]?+?Dodecanol)/SiO₂?CP had excellent reusability after three cycles.