Isomorphism in electron-pair densities of atoms

The spherically averaged electron-pair intracule (relative motion) h(u) and extracule (center-of-mass motion) d(R) densities are a couple of densities which characterize the motion of electron pairs in atomic systems. We study a generalized electron-pair density (q; a, b) that represents the probability density function for the magnitude of two-electron vector a r _j +b r _k of any pair of electrons j and k to be q, where a and b are nonzero real numbers. In particular, h(u)=g(u;1, −1) and d(R) = . It is shown that the scaling property of the Dirac delta function and the inversion symmetry of orbitals in atoms due to the central force field generate several isomorphic relations in the electron-pair density (q; a, b) with respect to the two parameters a and b. The approximate isomorphism d(R)≅8h(2R) known in the literature between the intracule and extracule densities is a special case of the present results. Received: 24 May 2000 / Accepted: 18 July 2000 / Published online: 27 September 2000     

On the inner and outer radial density functions

Starting from the two-electron radial density D ₂(r ₁,r ₂), a generalized partitioning of the one-electron radial density function D(r) into two component densities D _a (r) and D _b (r) is discussed for many-electron systems. The literature partitioning (Koga and Matsuyama Theor Chem Acc 115:59, 2006) of D(r) into the inner D _<(r) and outer D _>(r) radial densities is shown to minimize the average variance of the two component density functions D _a (r) and D _b (r). It is also found that the average radial separation halved, , constitutes a lower bound to the standard deviation σ of D(r).     

Inner and outer radial density functions in many-electron atoms

When any two electrons are considered simultaneously, the radial density function D(r) in many-electron atoms is shown to be rigorously separated into inner D _<(r) and outer D _>(r) radial densities. Accordingly, radial properties such as the electron–nucleus attraction energy V _en and the diamagnetic susceptibility χ _d are the sum of the inner and outer contributions. The electron–electron repulsion energy V _ee has an approximate relation with the minus first moment of the outer density D _>(r). For the 102 atoms He through Lr in their ground states, different characteristics of local maxima in the radial densities D _<(r), D _>(r), and D(r) are reported based on the numerical Hartree-Fock wave functions. Relative contributions of the inner and outer components to V _en and are also discussed for these atoms.     

Stereo-dynamics study of O + HCl → OH + Cl reaction on the <Superscript>3</Superscript>A″, <Superscript>3</Superscript>A′, and <Superscript>1</Superscript>A′ states

Using three accurate potential energy surfaces of the ³A″, ³A′, and ¹A′ states constructed recently, we present a quasi-classical trajectory (QCT) calculation for O + HCl (v = 0, j = 0) → OH + Cl reaction at the collision energies (E _col) of 14.0–20.0 kcal/mol. The three angular distribution functions—P(q_r ) P(\theta_{r} ) , P(j_r ) P(\varphi_{r} ) , and P(q_r ,j_r ) P(\theta_{r} ,\varphi_{r} ) , together with the four commonly used polarization-dependent differential cross-sections, \frac2ps \fracds₀₀ dw_t , \frac2ps \fracds₂₀ dw_t , \frac2ps \fracds_{22 +} dw_t , \textand \frac2ps \fracds_{21 -} dw_t {\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{00} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{20} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{22 + } }}{{d\omega_{t} }}},\,{\text{and}}\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{21 - } }}{{d\omega_{t} }}} are exhibited to get an insight into the alignment and the orientation of the product OH radical. There is a similar behavior of the tendency scattering direction for the two triplet electronic states (³A″ and ³A′)—backward scattering dominates, however, forward scattering prevails for the case of ¹A′ state. Also, obvious differences have been found in the stereo-dynamical information, which reveals the influences of the potential energy surface and the collision energy. The degrees of polarization and the influence of the collision energy on the stereo-dynamics characters of the title reaction are both demonstrated in the order of ³A′ > ³A″ > ¹A′.     

Quasielastic light scattering study of chemically crosslinked gelatin solutions and gels

Quasielastic light scattering measurements are reported for experiments performed on mixtures of gelatin and glutaraldehyde (GA) in the aqueous phase, where the gelatin concentration was fixed at 5 (w/v) and the GA concentration was varied from 1×10⁻⁵ to 1×10⁻³ (w/v). The dynamic structure factor, S(q,t), was deduced from the measured intensity autocorrelation function, g ₂(τ), with appropriate allowance for heterodyning detection in the gel phase. The S(q,t) data could be fitted to S(q,t)=Aexp(−D _f q ² t)+Bexp(−t/τ_c)^β, both in the sol (50 and 60 ^∘C) and gel states (25 and 40 ^∘C). The fast-mode diffusion coefficient, D _f showed almost negligible dependence on the concentration of the crosslinker GA; however, the resultant mesh size, ξ, of the crosslinked network exhibited strong temperature dependence, ξ∼(0.5−χ)^1/5exp(−A/RT) implying shrinkage of the network as the gel phase was approached. The slow-mode relaxation was characterized by the stretched exponential factor exp(−t/τ_c)^β. β was found to be independent of GA concentration but strongly dependent on the temperature as β=β₀+β₁ T+β₂ T ². The slow-mode relaxation time, τ_c, exhibited a maximum GA concentration dependence in the gel phase and at a given temperature we found τ_c(c)=τ₀+τ₁ c+τ₂ c ². Our results agree with the predictions of the Zimm model in the gel case but differ significantly for the sol state. Received: 25 May 1999 /Accepted in revised form: 27 July 1999     

Synthesis and Spectroscopic Characterization of Two Different Types of Heterobimetallic Glycolate Complexes of Niobium(V)

An entirely new class of heterobimetallic homoleptic glycolate complexes of the type Nb(OGO)₃{Ta(OGO)₂} [where G=CMe₂CH₂CH₂CMe₂ (G¹) (3); CMe₂CH₂ CHMe(G²) (4); CHMeCHMe (G³) (5); CH₂CMe₂CH₂ (G⁴) (6); CMe₂CMe₂(G⁵) (7); CH₂CHMeCH₂ (G⁶) (8); CH₂CEt₂CH₂ (G⁷) (9); CH₂CMe(Prⁿ)CH₂ (G⁸) (10)] have been prepared by the reactions of Nb(OGO)₂(OGOH) [G=G¹ (1a); G² (1b); G³ (1c); G⁴ (1d); G⁵ (1e); G⁶ (1f); G⁷ (1g); G⁸ (1h)] with Ta(OGO)₂ (OPrⁱ) (G=G¹ (2a); G² (2b); G³ (2c); G⁴ (2d); G⁵ (2e) G⁶ (2f); G⁷ (2g); G⁸ (2h). In addition to the novel derivatives (2)–(10), our earlier investigations on heterobimetallic glycolate-alkoxide derivatives have been extended to derivatives of the type Nb(OGO) [where M=A1 n=3, G=G³ (11);G⁴ (12); G⁶ (13) G⁷ (14); G^s (15); G⁹=CH₂CH₂CH₂ (16) and M=Ti (n=4, G=G⁴) (17), Zr(n=4,G=G⁴) (18)], which are conveniently prepared by the reactions of metalloligands Nb(OGO)₂(OGOH) [G=G³ (1c); G⁴ (1d); G⁶ (1f); G⁷ (1g); G⁸ (1h); G⁹ (1i)] with different metal alkoxides. All of these new complexes have been characterized by elemental analyses, molecular weight determinations, and spectroscopic (I.r. and ¹H, ²⁷Al-n.m.r.) studies. Structural features of the new derivatives have been elucidated on the basis of molecular weight and spectroscopic data.     

Nonlinear viscoelasticity of polystyrene solutions. I. Strain-dependent relaxation modulus

Strain-dependent relaxation moduli G(t,s) were measured for polystyrene solutions in diethyl phthalate with a relaxometer of the cone-and-plate type. Ranges of molecular weight M and concentration c were from 1.23 × 10⁶ to 7.62 × 10⁶ and 0.112 to 0.329 g/cm³. Measurements were performed at various magnitudes of shear s ranging from 0.055 to 27.2. The relaxation modulus G(t,s) always decreased with increasing s and the relative amount of decrease (i.e.,–log[G(t,s)/G(t,0)]) increased as t increased. However, the detailed strain dependences of G(t,s) could be classified into two types according to the M and c of the solution. When cM < 10⁶, the plot of log G(t,s) versus log t varied from a convex curve to an S-shaped curve with increasing s. For solutions of cM > 10⁶, the curves were still convex and S-shaped at very small and large s, respectively, but in a certain range of s (approximately 3 < s < 7) log G(t,s) decreased rapidly at short times and then very slowly; a peculiar inflection and a plateau appeared on the plot of log G(t,s) versus log t. The strain-dependent relaxation spectrum exhibited a trough at times corresponding to the plateau of log G(t,s). The longest relaxation time τ₁(s) and the corresponding relaxation strength G₁(s) were evaluated through the “Procedure X” of Tobolsky and Murakami. The relaxation time τ₁(s) was independent of s for all the solutions studied while G₁(s) decreased with s. The reduced relaxation strength G₁(s)/G₁(0) was a simple function of s (The plot of log G₁(s)/G₁(0) against log s was a convex curve) and was approximately independent of M and c in the range of cM <10⁶. This behavior of G₁(s)/G₁(0) was in agreement with that observed for a polyisobutylene solution and seems to have wide applicability to many polymeric systems. On the other hand, log G₁(s)/G₁(0) as a function of log s decreased in two steps and decreased more rapidly when M or c was higher. It was suggested that in the range of cM < 10⁶, a kind of geometrical factor might be responsible for a large part of the nonlinear behavior, while in the range of cM > 10⁶, some “intrinsic” nonlinearity of the entanglement network system might be important.     

Spectra and structure of organophosphorus compounds: XLIX. Microwave,infrared, and Raman spectra,electric dipole moment,molecular structure,and ab initio calculations of dimethylphosphonothioic fluoride

The microwave spectra of (CH₃)₂PSF, (CH₃)(CD₃)PSF, (CD₃)₂PSF, and (CH₃)₂P³⁴SF have been investigated from 20.0 to 40.0 GHz. Botha-type R branch andc-type Q branch transitions have been measured in the ground states of each isotopic species. From a least-square adjustment to fit 12 rotational constants, the following structural parameters were obtained:r(P–F)=1.582 ± 0.003 Å;r(P=S)=1.902 ± 0.001 Å;r(P-C)=1.800 ± 0.001 Å;r(C-H)=1.088 ± 0.002 Å; HCP=109.28 ± 0.12°; SPF=114.50 ± 0.13°; and SPC=116.33 ± 0.06°. From Stark effect measurements, the dipole moment components have been determined to be ¦ _a ¦ =3.556 ± 0.005; ¦ _c ¦=2.026 ± 0.009; and ¦ _t ¦=4.093 ± 0.009 (D). The Raman spectra (3200 to 100 cm^–1) of each isotopic species have been measured for the solid, and liquid and qualitative depolarization values obtained. Additionally, the mid-infrared spectra (3200 to 500 cm^–1) of the solids have been recorded. Proposed assignments of the normal modes have been made on the basis of Raman depolarization values and group frequencies which are supported by normal coordinate analysis utilizing an ab initio force field. Optimized structural parameters have been obtained with both the 3-21G^* and 6-31G^* basis sets. These results are compared to the corresponding quantities for several similar molecules.For part XLVIII, seeJ. Raman Spectrosc.1922,23, 107.     

Different coordination modes of the dimethyldisulfide ligand in trimethylplatinum(IV) complexes

The reaction of [PtMe₃(bpy)(Me₂CO)](BF₄) (2) (prepared from [PtMe₃I(bpy)] (1) plus Ag(BF₄)) with MeSSMe resulted in the formation of [PtMe₃(bpy)(MeSSMe-κS)](BF₄) (3). A single-crystal X-ray diffraction analysis revealed in the octahedral Pt(IV) complex (configuration index: OC-6-33), a conformation of the monodentately κS bound MeSSMe ligand (C–S–S–C 92.7(4)°) being very close to that in non-coordinated MeSSMe, thus allowing some hyperconjugative interaction stabilizing the S–S bond. The reaction of [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (4; 18C6 = 18-crown-6, Hpz = pyrazole) with Ag(BF₄) and MeSSMe resulted in the formation of dinuclear complexes [(PtMe₃)₂(μ-pz)₂(μ-MeSSMe)] existing at room temperature in acetone solution as different fast interconverting isomers. At –40 °C, two isomers with a μ-1κS:2κS (5a) and a μ-1κS:2κS′ (5b) coordinated MeSSMe ligand in the ratio 2:1 could be identified ¹H NMR spectroscopically. DFT calculations of type 5 complexes revealed the existence of two conformers with a μ-MeSSMe-1κS:2κS ligand, which differ mainly in the C–S–S–C dihedral angle (66.4 vs. 180.0° 6a/6a′). They have essentially the same energy and a very low activation barrier in acetone as solvent (1.3 kcal/mol) for their mutual interconversion. A further equilibrium structure was identified to be an isomer having a μ-MeSSMe-1κS:2κS′ ligand (6b) that proved to be only 1.9 kcal/mol higher in energy than 6a/6a′.     

Syntheses and crystal structures of NH4Ag2(AsS2)3 and (NH4)5Ag16(AsS4)7 with a discussion of (NH4)Sx polyhedra

Summary The atomic arrangements within the structures of NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; space group P2₁/n;R(F)=0.042] and (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; space group Cc;R(F)=0.073] were determined from single crystal X-ray data. In these two compounds the coordination spheres of the Ag atoms are quite different. In NH₄Ag₂(AsS₂)₃, the Ag atoms exhibit a [2+2]- and a [3+1]-coordination to S atoms up to 3.3 Å and with Ag atom neighbours at 2.93 Å and 3.05 Å respectively. In (NH₄)₅Ag₁₆(AsS₄)₇, the Ag atoms are — with one exception- [4] coordinated (Ag-S<3.3 Å) and the distances to further Ag atom neighbours are greater than 3.1 Å. NH₄Ag₂(AsS₂)₃ represents an ordered cyclo-thioarsenate(III) with three-membered As₃S₆ rings, (NH₄)₅Ag₁₆(AsS₄)₇ a neso-thioarsenate(V) with two split Ag atom positions. Both compounds were synthesized under moderate hydrothermal conditions.

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Synthesen und Kristallstrukturen von NH₄Ag₂(AsS₂)₃ und (NH₄)₅Ag₁₆(AsS₄)₇ mit einer Diskussion über (NH₄)S_x Polyeder

Zusammenfassung Die Atomanordnungen in den Strukturen von NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; Raumgruppe P2₁/n;R(F)=0.042] und (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; Raumgruppe Cc;R(F)=0.073] wurden anhand von röntgenographischen Einkristalldaten bestimmt. In diesen beiden Verbindungen sind die Koordinationsverhältnisse um die Ag-Atome sehr unterschiedlich. In NH₄Ag₂(AsS₂)₃ besitzen die Ag-Atome bis 3.3 Å eine [2+2]- und [3+1]-Koordination durch S-Atome mit weiteren Ag-Atomen bei 2.93 Å und 3.05 Å. In (NH₄)₅Ag₁₆(AsS₄)₇ sind die Ag-Atome mit einer Ausnahme [4]-koordiniert (Ag-S < 3.3 Å), und die Abstände zu weiteren Ag-Atomen sind größer als 3.1 Å. NH₄Ag₂(AsS₂)₃ stellt ein geordnetes Cyclothioarsenat(III) mit dreigliedrigen As₃S₆-Ringen dar, (NH₄)₅Ag₁₆(AsS₄)₇ ein Nesothioarsenat (V) mit zwei aufgespaltenen Ag-Positionen. Beide Verbindungen wurden unter mäßigen Hydrothermalbedingungen synthetisiert.

     

Radial electron-pair densities in momentum space and shell structure of atoms

 The radial electron-pair intracule (relative motion) H(u) and extracule (center-of-mass motion) D(R) densities in position space were known to reveal four types of maxima which are related to the four inner electron shells, K, L, M, and N, of atoms. The corresponding radial electron-pair intracule Hˉ(v) and extracule Dˉ(P) densities in momentum space are studied for the 102 atoms from He (atomic number Z=2) to Lr (Z=103). The densities Hˉ(v) and Dˉ(P) are found to have either one maximum or two maxima, and the numbers of maxima in Hˉ(v) and Dˉ(P) are the same for 98 atoms. For these atoms, the locations υ _max and P _max and the heights Hˉ _max and Dˉ _max of the corresponding maxima satisfy the approximate relations υ _max ≅ 2P _max and Hˉ _max ≅Dˉ _max /2. On the basis of their Z-dependence, the maxima in Hˉ(v) and Dˉ(P) of the 102 atoms are classified into five types. Shell-pair decompositions of the radial densities show that these maxima reflect five outer electron shells of atoms. Received: 24 January 2001 / Accepted: 12 March 2001 / Published online: 13 June 2001     

Reactivity of diacetylplatinum(II) complexes: oxidative addition of alkyl halides and crystal structures of acetyl platinum(IV) complexes

Diacetylplatinum(II) complexes [Pt(COMe)₂(N^N)] (N^N = bpy, 3a; 4,4′-t-Bu₂-bpy, 3b) were found to undergo oxidative addition reactions with organyl halides. The reaction of 3a with methyl iodide and propargyl bromide led to the formation of the cis addition products (OC-6-34)-[Pt(COMe)₂(R)X(bpy)] (R = Me, X = I, 4a; CH₂C≡CH, X = Br, 4k). Analogous reactions of 3a with ethyl iodide, benzyl bromide, and substituted benzyl bromides, 3-(bromomethyl)pyridine, 2-(bromomethyl)thiophene, allyl bromide, and cyclohex-2-enyl bromide led to exclusive formation of the trans addition products (OC-6-43)-[Pt(COMe)₂(R)X(bpy)] (X = I, R = Et, 4b; X = Br, R = CH₂C₆H₅, 4c; CH₂C₆H₄(o-Br), 4d; CH₂C₆H₄(p-COOH), 4e; CH₂-3-py (3-pyridylmethyl), 4f; CH₂-2-tp (2-thiophenylmethyl), 4g; CH₂CH=CH₂, 4h; c-hex-2-enyl (cyclohex-2-enyl), 4i). All complexes 4 were characterized by microanalysis, ¹H and ¹³C NMR and IR spectroscopy. Additionally, complexes 4a, 4f, and 4g were characterized by single-crystal X-ray diffraction analyses. Reactions of 3a and 3b with o-, m- and p-bis(bromomethyl)benzene, respectively, led to the formation of dinuclear platinum(IV) complexes [{Pt(COMe)₂Br(N^N)}₂-{μ-(CH₂)₂C₆H₄}] (5). These complexes were characterized by microanalysis, IR spectroscopy, and depending on their solubility by ¹H and ¹³C NMR spectroscopy, too. A single-crystal X-ray diffraction analysis of complex [{Pt(COMe)₂Br(bpy)}₂{μ-m-(CH₂)₂C₆H₄}] (5b) confirmed its dinuclear composition. The solid-state structures of 4a, 4f, 4g, and 5b are discussed in terms of C–H···O and O–H···O hydrogen bonds as well as π–π stacking between aromatic rings.     

Surfactant induced softening in gelatin hydrogels

Effect of binding of three surfactants, alpha olefin sulfonate (AOS, anionic), Triton-X100 (TX-100, non-ionic) and cetyl trimethyl ammonium bromide (CTAB, cationic) to the hydrogels of gelatin was studied at room temperature (25 °C) by dynamic light scattering and oscillatory rheology with surfactant concentrations (20-100 mM) much larger than the critical micellar concentrations (cmc) of these surfactants. The measured intensity auto-correlation function of light scattered from gels revealed the presence of finite heterodyne contribution ≈0.11 ± 0.01 that increased to ≈0.25 ± 0.02 after transition to the soft gel state indicating a softening process for surfactant concentrations exceeding 50 mM. The dynamic structure factor S(q, t) of micelle bound gelatin gels revealed two clearly identifiable relaxation modes namely; the fast mode, S(q, t) ∼ exp · (−D_fq²t) for t ? 1 ms and a stretched exponential mode, S(q, t) ∼ exp · −(t/τ_c)^β for 1 ms ? t ? 1 s. This behaviour was universal with β ≈ 0.85 ± 0.04 independent of the surfactant type. The low frequency (1.5 rad/s) storage modulus G′, loss modulus G″ and tan δ behaviour revealed a gradual softening of the gel independent of the surfactant type. The exponent (β) fast mode diffusivity (D_f) and stretched exponential mode relaxation time were found to be less sensitive to this softening transition.     

High-Energy X-ray Diffraction and MD Simulation Study on the Ion-Ion Interactions in 1-Ethyl-3-methylimidazolium Bis(fluorosulfonyl)amide

Ion-ion interactions or liquid structures in low-viscosity ionic liquid, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide, [C₂mIm⁺][FSA^?] were investigated by high-energy X-ray diffraction (HEXRD) experiments and molecular dynamics (MD) simulations. Experimental X-ray structure factor, S ^exp(q) obtained from the HEXRD was successfully deconvoluted into the intra- and the intermolecular components, S _intra ^exp (q) and S _inter ^exp (q), respectively, by taking into account the population of cis and trans conformers of the FSA anion to give the corresponding radial distribution functions, G _intra ^exp (r) and G _inter ^exp (r), respectively. The G _inter ^exp (r) exhibits the peaks at 3.5, 4.6 and 5.4 Å, which is well represented by theoretical radial distribution function, G _inter ^MD (r) obtained from MD simulations. From the space distribution function, SDF calculated by MD simulations, it was found that static structure (distance and orientation) of the nearest neighbor intermolecular interaction between cation and anion in [C₂mIm⁺][FSA^?] is similar to its analogous ionic liquid, [C₂mIm⁺][TFSA^?] where TFSA is bis(trifluoromethanesulfonyl)amide.     

Structure cristalline d'un phosphochromate acide de cuivre potassium: CuK2H2(PCrO7)2

CuK₂H₂(PCrO₇)₂ is monoclinic, P2₁/c, with a unit cell: a=9.559(5)Å; b=7.196(5)Å; c=8.983(5)Å;β=93.73(5)°; Z=2; and D=2.87g/cm³.The crystal structure of this compound has been resolved by using 1938 independent reflections with a final R value of 0.03. The main feature of this compound is the existence of the mixed pyro-group CrPO₇, up to now the first to be described.     

Some properties of the structure factor S(q) in two-dimensional classical liquids near freezing

We explore general properties of the main peak of the structure factor S(q) near the melting temperature T _melt in liquids confined in two dimensions, especially for the one component plasma model and for monatomic liquids interacting through inverse twelfth-power potentials. Those properties are the height of the peak, S(q _m), where q _m is the position of maximum in the peak, and the ratio between S(q _m) and q _m/Δq, where 2Δq is the width of the peak. The results obtained are then compared with those for similar systems in three dimensions. Other magnitude that we use to compare two-dimensional and three-dimensional simple liquids is r _m/Δr, where r _m is the position of the main peak in the pair distribution function g(r) and 2Δr is the width of that peak.     

Synthesis,structure and electrochemistry of dithiocarbamato phenthiolate oxo-molybdenum(IV) complexes [MoO(SΦ)2(S2CNEt2)]-

The reaction of Mo(0) complex [Mo(CO)₄(S₂CNEt₂)]- with phenthiolate [Et₄N]SΦ in acetonitrile in the presence of small amount of air affords a new oxo-molybdenum complex [MoO(SΦ)₂(S₂CNEt₂)], which crystallizes in two forms of crystals. [Et₄N][MoO(SΦ)₂Φ(S₂CNEt₂)] (1a) and [Et₄N][MoO(SΦ)₂(S₂CNEt₂)]Φ(CH₃)₂CHOH (1b). The structures of 1a and 1b were determined from three-dimensional X-ray data. 1a crystallizes in the monoclinic, space group C_e with a=12.321(4), b=15.245(4), c=16.087(9)Å; β= 98.44(4)Φ, V=2989ų, Z=4, D_c = 1.35g/cm³ and R=0.031 for 2434 reflections [I>36(I)]. 1b crystallizes in the monoclinic space group F2₁/n with a=9.861(1), b=20.357(3), c=17.122(5)Å; β= 92.27 (2)*, V=3434.3ų, Z=4; D_e = 1.29g/cm³ and R= 0.051 for 2852 independent reflections [I>3σ(I)]. The structures of 1a and 1b reveal that the anion [MoO(SΦ)₂(S₂CNEt₂)]- contains a single oxo ligand coordinating to a molybdenum(IV) and the geometry around Mo(IV) atom is a distorted square pyramid. Interestingly, the solvate molecule isopropanol of 1b is linked to oxo group by a hydrogen-bond of 1.928Å, leading to the increase of Mo?O bond distance (1.718Å). Mo—S distances are 2.44 and 2.39Å. The electrochemical behavior of 1 was discussed also.     

Synthesis of chiral α-ethylphenylamine salts of tartaric acid and novel application to cyanosilylation of prochiral ketones

Abstract  

Chiral α-ethylphenylamine tartaric acid salts were synthesized from α-ethylphenylamine by direct reaction with chiral tartaric acid. The crystal structure of S-(−)-α-ethylphenylamine-(2R,3R)-(−)-dihydroxybutanedioic acid was determined. The crystal is monoclinic, of space group P2_1/n , with a = 6.331(5) ?, b = 14.209(11) ?, c = 7.495(6) ?, α = 90.00o, β = 107.000(13)o, γ = 90.00o, λ = 0.7103 Ǻ, V = 644.7(9), Z = 2, D _c = 1.397 g/cm³, M _r  = 271.27 and F(000) = 288, R = 0.0477, and ωR = 0.0838 for 1388 observed reflections with I > 2σ(I). We then used the chiral α-ethylphenylamine tartaric acid salts as catalysts in the cyanosilylation of prochiral ketones, and moderate conversions were obtained.     

Characteristic lengths and the structure of salt free polyelectrolyte solutions. A small angle neutron scattering study

We have studied salt free semi dilute polyelectrolyte solutions by small angle neutron scattering. Specific labelling associated with an extrapolation method has allowed the separation of the form factor of a single polyelectrolyte chainS ₁(q) and the structure factorS ₂(q). Two lengths are deduced from these two factors: the persistence lengthb _t which characterizes the electrostatic interactions along the chain by a fitting ofS ₁(q) with calculation of the scattering function for a wormlike chain, and fromS ₂(q),q _m ^–1 which characterizes the interactions between chains. These two lengths vary in the same way with the concentration of polyions (b _t C _p ^–1/2 ,q _m ^–1 C _p ^–1/2 ) and a constant relation exists between them: only one length is then necessary to describe the structure of polyelectrolyte soltuion on this semidilute concentration range.Laboratoire Commun CEA-CNRS.