Reactions of [NiIII(cyclam)] with aqueous sulfur dioxide: Exhibition of a deuterium isotope effect and catalysis by chloride and bromide

One unit of S(IV) (SO₂ or SHO₃^?) is oxidized per 2 units of [Ni^III(cyclam)] species to obtain sulfate. Kinetic analyses have been done by varying the acidities (0.013 ? [H⁺] ? 1.0 M) and halide concentrations (0.000 ? [X^?] ? 0.012 M; X=Cl and Br) at constant ionic strength (μ = 1.0 M). The rate law that incorporates the [X^?] and [H⁺] dependence is ?d[Ni^III]_T/dt=2k[Ni^III]_T[S(IV)]_T where 2k={k_a[H⁺] + k_bK + kK′_X[H⁺] [X^?] + kK′_XK[X^?]} {[H⁺] + K}^?1 {1 + K′_X[X^?]}^?1, here k_a=87 ± 7 M^?1 s^?1, k_b=(2.5 ± 0.5)×10³ M^?1 s^?1 and pK = 1.8 ± 0.2. Rate constants k_a and k_b are attributed to the reactions of [Ni^III(cyclam) (H₂O)₂]³⁺ with SO₂ and SHO₃^?, respectively. Monohalo species apparent equilibrium constants K′_Cl=(1600 ± 400) M^?1 and K′_Br=(190 ± 20) M^?1 and rate constants k=80 ± 8 M^?1 s^?1 and k = 140 ± 15 M^?1 s^?1 are ascribed to the protonated pathway, involving the [Ni^III(cyclam) (H₂O)X]²⁺ and SO_2(aq) reaction pairs. The other two rate constants of k=(5 ± 1)×10³ M^?1 s^?1 and k=(3.1 ± 0.5)×10⁴ M^?1 s^?1, refer to the deprotonated pathway and are assigned to the [Ni^III(cyclam) (H₂O)X]²⁺ /SHO₃^? redox couple. A deuterium H₂O / D₂O isotope effect of 2.1–2.8 can be attributed partially to an equilibrium isotope effect at low acidity though a small kinetic isotope (2.5 ± 0.5) effect is evident for the dihydrogen sulfito pathway, k_a. The kinetic isotope effect and the absence of sulfite radical scavenging effects are explained by a mechanism entailing migration of a hydride from sulfur to the Ni^III center to produce a Ni^III—H species, which rapidly comproportionates, and S(VI). © 1993 John Wiley & Sons, Inc.     

Comparative preparations of homoleptic hydridic anions of iron and ruthenium using solution-based organometal hydrogenation techniques

A study of the preparations of the complex hydridic anions [MH(6)](4)(-) (M = Fe and Ru) reveals a number of distinctive features. Here a soluble homoleptic ruthenium hydride has been prepared for the first time. For example, both FeX(2) and [Ru(eta(4)-1,5-COD)X(2)], X = Cl and Br, react with PhMgBr solutions under hydrogen to produce the title compounds. The benzene liberated in these reactions is more readily hydrogenated in the case of a homogeneous room temperature ruthenium hydride preparation to both cyclohexane and cyclohexene. The (1)H NMR spectroscopic data show that the two complex anions have hydride absorptions in the low-frequency region, delta -20.3 and -14.7, respectively. Further, (1)H spin-lattice relaxation times (T(1)) for M-H are longer in the case of Ru vs Fe.     

三价铬与丙二酸形成的配合物的热解过程研究

利用热重分析及原位红光谱等方法，定性，定量地研究了三价铬和丙二酸形成的配合物［Ｃｒ（Ｃ３Ｈ２Ｏ４）（Ｈ２Ｏ）４］［Ｃｒ（Ｃ３Ｏ４）２（Ｈ２Ｏ２）］．４Ｈ２Ｏ的热解过程，提出了室温至４００℃下的详细热解途径。基于多种实验结果，分析了螯合物中六员环的化学断裂方式，并由配合物的快原子轰击质谱（ＦＡＢ－ＭＳ）加以佐证。     

Electron paramagnetic resonance study of partially oriented clay platelets intercalated with copper(II) 1,4,8,11-tetraazacyclotetradecane

Electron paramagnetic resonance (EPR) spectra of powder and oriented films of montmorillonite, hectorite, and saponite intercalated with [Cu(cyclam)](2+) (cyclam = 1,4,8,11-tetraazacyclotetradecane) exhibit three components: an orientation-dependent component without hyperfine features, an orientation-dependent component with hyperfine features, and an orientation-independent component without hyperfine feature. EPR spectra of [Cu(cyclam)](2+)-saponite, which exhibit only two components and the best resolved hyperfine features, were simulated. The spectra indicate that a large portion of the saponite platelets are inclined to the glass surface, although they tend to align with their basal planes parallel to the glass surface. The orientation-dependent spectra could be simulated by introducing a Gaussian distribution with a standard deviation of 20 degrees for the inclination angle. The standard deviation may be used as a disorder parameter for the microcrystals assembled on glass plates. Spectral simulation also shows that the CuN(4) plane of [Cu(cyclam)](2+) is parallel to the clay layers. EPR spectra of some other partially oriented systems are also discussed.     

Hydrogen bond studies: 80. A deuteron magnetic resonance and infrared spectroscopic study of the water molecule in lithium formate monohydrate,LiHCOO · H2O

A deuteron magnetic resonance and infrared study of the water molecules in lithium formate monohydrate, LiHCOO · H₂O, has been made. The quadrupole coupling constants (e²qQ/h) and asymmetry parameters (η) were found to be 198.7±0.4 and 231.3±0.6 kHz, and 0.060±0.005 and 0.097±0.003, respectively, at 25 ° C.An interpretation is given of the infrared spectra in the OH-stretching region in terms of intra- and intermolecular couplings of the water molecules. It is found that the water molecules are vibrationally distorted by their environments such that the OH-stretching modes consist of independent stretchings of the two O-H bonds.     

Integrability and ergodicity of classical billiards in a magnetic field

We consider classical billiards in plane, connected, but not necessarily bounded domains. The charged billiard ball is immersed in a homogeneous, stationary magnetic field perpendicular to the plane. The part of dynamics which is not trivially integrable can be described by a bouncing map. We compute a general expression for the Jacobian matrix of this map, which allows us to determine stability and bifurcation values of specific periodic orbits. In some cases, the bouncing map is a twist map and admits a generating function. We give a general form for this function which is useful to do perturbative calculations and to classify periodic orbits. We prove that billiards in convex domains with sufficiently smooth boundaries possess invariant tori corresponding to skipping trajectories. Moreover, in strong field we construct adiabatic invariants over exponentially large times. To some extent, these results remain true for a class of nonconvex billiards. On the other hand, we present evidence that the billiard in a square is ergodic for some large enough values of the magnetic field. A numerical study reveals that the scattering on two circles is essentially chaotic.     

Structure and dynamic stability of cyclodextrin inclusion complexes with 1,4-disubstituted bicyclo[2.2.2]octanes

The properties of inclusion complexes of 1,4-di-R-bicyclo[2.2.2]octaves (R = H (1), Me (2), Cl (3), Br (4), and OH (5)) with cyclodextrins have been studied by NMR, microcalorimetry, and force-field computations. The compounds2 and3 (but not the other compounds) give dynamically stable 1:2 guest-host complexes with -cyclodextrin. Microcalorimetry of5 in water indicates a moderately strong 1:1 complex with - but weak complexes with - or -cyclodextrin. The behaviour depends on the subtle interplay size, polarity, hydrophobicity and type of solvent.     

Critical factors for high-performance physically adsorbed (dynamic) polymeric wall coatings for capillary electrophoresis of DNA

Physically adsorbed (dynamic) polymeric wall coatings for microchannel electrophoresis have distinct advantages over covalently linked coatings. In order to determine the critical factors that control the formation of dynamic wall coatings, we have created a set of model polymers and copolymers based on N,N-dimethylacrylamide (DMA) and N,N-diethylacrylamide (DEA), and studied their adsorption behavior from aqueous solution as well as their performance for microchannel electrophoresis of DNA. This study is revealing in terms of the polymer properties that help create an "ideal" wall coating. Our measurements indicate that the chemical nature of the coating polymer strongly impacts its electroosmotic flow (EOF) suppression capabilities. Additionally, we find that a critical polymer chain length is required for polymers of this type to perform effectively as microchannel wall coatings. The effective mobilities of double-stranded (dsDNA) fragments within dynamically coated capillaries were determined in order to correlate polymer hydrophobicity with separation performance. Even for dsDNA, which is not expected to be a strongly adsorbing analyte, wall coating hydrophobicity has a deleterious influence on separation performance.     

Hydrogen bond studies: Part 118. A deuteron magnetic resonance study of BeSO4· 4D2O and Li2SO4· D2O

The electric field gradient (EFG) tensors at the deuterons in the water molecules in BeSO₄ · 4D₂O at 25°C are reported. The quadrupole coupling constants (e²Q/h) and asymmetry parameters (η) for the two independent deuterons are 181.1(4) and 194.8(3) kHz, and 0.226(4) and 0.123(3), respectively. The EFG tensor corresponding to the smallest e²qQ/h is considerably distorted by the beryllium ion, which causes a high η value as well as a deviation of the y-principal axis by 21.8(6)° from the normal to the water molecule plane. A redetermination of the EFG tensors at the deuterons in the water molecule in Li₂SO₄ · D₂O at 25°C and ?110°C is also reported. The e²Q/h and η values for the two deuterons are 236.6(1.2) and 239.8(1.1) kHz, and 0.091(8) and 0.126(7), respectively, at ?110°C. The corresponding e²qQ/h and η values for the averaged EFG tensor at 25°C are 125.8(1.1) kHz and 0.813(13), respectively. The results are in good agreement with those from the pioneer work by Ketudat and Pound, 20 years ago on the same compound.