Metal complexation of crosslinked polyacrylamide-supported dithiocarbamates: Effect of the molecular character and extent of crosslinking on complexation

Dithiocarbamate functions were incorporated into different polyacrylamide matrices crosslinked with a flexible and hydrophilic crosslinking agent, tetraethyleneglycol diacrylate (TEGDA), and their complexation behaviours were investigated. Crosslinked polyacrylamides with varying extents of the tetrafunctional TEGDA crosslinks were prepared by free radical solution polymerization at 60°C using potassium persulphate as initiator in ethanol. The dithiocarbamate functionality was incorporated into these polyacrylamides by a two-step polymer-analogous reaction involving (i)trans-amidation with ethylenediamine and (ii) dithiocarbamylation of the aminopolyacrylamide with carbon disulphide and alkali. The complexations of dithiocarbamate with Cu(II), Ni(II), Zn(II), Co(II) and Hg(II) ions were followed under different conditions. The metal ion intake varied with the extent of the crosslinking agent and the observed trend in complexation is Hg(II) > Cu(II)> Zn(II)> Co(II)> Ni (II). The time-course of complexation, the possibility of recycling, swelling characteristics, and spectral and thermal analyses were carried out. The thermal stability increases upon complexation with metal ions.     

Functionalization of crosslinked poly(4-vinylpyridine) and poly(4-vinylpyridine-co-styrene) with permanganate species: Preparation of poly(4-vinylpyridinium permanganate)s and their use as oxidizing reagents

Crosslinked poly(4-vinylpyridine) and poly(4-vinylpyridine-co-styrene) were functionalized with permanganate group to afford the corresponding poly[4-vinyl(pyridinium permanganate)] resin. These resins were found to selectively oxidize alcohols to corresponding carbonyl compounds. These insoluble functionalized polymers possess the desired characteristics of the polymeric reagents, including operational simplicity, filterability, and regenerability. The influence of solvent, duration of reaction, and molar excess of the reagent in these oxidation reactions was investigated to find out the optimum conditions for effective oxidation reactions. The reactions were found to be more facilitated in nonpolar solvents, and a large excess of the polymeric reagent did not have any significant effect on the extent of reactions. The poly[4-vinyl(pyridinium permanganate)] resin bears a contrast to KMnO₄ and other polymer-supported oxidizing agents like poly[4-vinyl(pyridinium chlorochromate)] in that it does not bring about the oxidation of the alcohol group directly attached to the ring structure.     

Solvent water tapes in two hydrates of μ‐oxo‐bis­[bis­(2,2′‐bipyridine‐κ2N,N′)(sulfato‐κO)iron(III)]

The title compound, [Fe₂O(SO₄)₂(C₁₀H₈N₂)₄], crystallizes as two different hydrates, viz. 11H₂O, (I), and 15H₂O, (II). The complex is binuclear, in which the two Fe^III atoms are coordinated in an octa­hedral geometry to four N atoms from the two bipyridine ligands, to one O atom from the sulfate ion and to an oxide ion on a twofold axis, which acts as a bridge between the symmetry‐related units. The Fe⋯Fe separation is 3.556 (4) Å and the Fe—O—Fe angle is 161.6 (2)° in (I); the corresponding values are 3.544 (1) Å and 165.8 (2)° in (II). In (II), one of the O atoms of the sulfate ion is disordered over two positions. In both compounds, the solvent water mol­ecules form slightly different one‐dimensional hydrogen‐bonded networks which pass along the c axis of the unit cell. In (I), three solvent water mol­ecules and, in (II), one solvent water mol­ecule, are situated on the twofold axis. In both (I) and (II), the central O atom of the metal complex lies on a twofold axis.     

Provably stable and time‐accurate extensions of Runge–Kutta schemes for CFD computations on moving grids

Extending fixed‐grid time integration schemes for unsteady CFD applications to moving grids, while formally preserving their numerical stability and time accuracy properties, is a nontrivial task. A general computational framework for constructing stability‐preserving ALE extensions of Eulerian multistep time integration schemes can be found in the literature. A complementary framework for designing accuracy‐preserving ALE extensions of such schemes is also available. However, the application of neither of these two computational frameworks to a multistage method such as a Runge–Kutta (RK) scheme is straightforward. Yet, the RK methods are an important family of explicit and implicit schemes for the approximation of solutions of ordinary differential equations in general and a popular one in CFD applications. This paper presents a methodology for filling this gap. It also applies it to the design of ALE extensions of fixed‐grid explicit and implicit second‐order time‐accurate RK (RK2) methods. To this end, it presents the discrete geometric conservation law associated with ALE RK2 schemes and a method for enforcing it. It also proves, in the context of the nonlinear scalar conservation law, that satisfying this discrete geometric conservation law is a necessary and sufficient condition for a proposed ALE extension of an RK2 scheme to preserve on moving grids the nonlinear stability properties of its fixed‐grid counterpart. All theoretical findings reported in this paper are illustrated with the ALE solution of inviscid and viscous unsteady, nonlinear flow problems associated with vibrations of the AGARD Wing 445.6. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of the Molecular Character and Degree of Crosslinking on the Interaction of Crosslinked Polyacrylamide-Supported Amines with Cu(Ii) Ions

Abstract

Amino groups were incorporated into polyacrylamides with 2?20 mol% of crosslinking agents by transamidation with ethylenediamine. Divinylbenzene, N,Nv′-methylene-bis-acrylamide, and tetraethyleneglycol diacrylate were used as the crosslinking agents. The complexation of these resins, which contain ligand functions in different macromolecular structural environments, was investigated with Cu(II) ions. The Cu(II) uptake of these different resins was correlated with the molecular character and degree of crosslinking in the polymer matrix. The time course and kinetics of complexation depend on the nature of the crosslinking agent in the polymer matrix. The swelling behavior of the uncomplexed and complexed resins, structural characteristics, and thermal decomposition behavior were followed by IR, EPR, and thermal analysis. The swelling characteristics of the complexed resins are lower than those of the uncomplexed resins. Complexation resulted in shifting of the IR absorptions. The EPR parameters depend on the nature of crosslinking and are in agreement with the distorted tetragonal geometry of the Cu(II) complexes. The thermal decomposition behavior also depends on the nature and the degree of crosslinking in the polymer matrix.     

Bromine Complexes of Polyvinylpyrrolidone Supports: A Mild Reagent for the Transformation of α‐Oxoketene Dithioacetals to β‐Oxothiolesters

When α‐oxoketene dithioacetals 1a–n were treated with the bromine complex of a copolymer of 1‐vinyl‐2‐pyrrolidone and 4‐vinylpyridine, the corresponding thiolcarboxylates 2a–n were formed in excellent yields. The reaction also works with other 1‐vinyl‐2‐pyrrolidone‐derived polymers as well as commercially available polyvinylpyrrolidone–bromine complexes. The method is suitable for preparing aliphatic, aromatic, and γ,δ‐unsaturated β‐oxothiolcarboxylates.     

S‐Alkylation of Soft Scorpionates

The alkylation reactions of soft scorpionates are reported. The hydrotris(S‐alkyl‐methimazolyl)borate dications (alkyl=methyl, allyl, benzyl), which were prepared by the reaction of Tm^Me anion and primary alkyl halides, have been isolated and structurally characterised. The reaction is, however, not universally successful. DFT analysis of these alkylation reactions (C?S versus B? H alkylation) indicates that the observed outcome is driven by kinetic factors. Extending the study to incorporate alternative imine thiones (mercaptobenzothiazole, bz; thiazoline, tz) led to the structural characterisation of di[aquo‐μ‐aquohydrotris(mercaptobenzothiazolyl)boratosodium], which contains sodium atoms in the κ³‐S,S,S coordination mode. Alkylation of Na[Tbz] and Na[tzTtz] leads to decomposition resulting in the formation of the simple S‐alkylated heterocycles. The analysis of the species involved in these reactions shows an inherent weakness in the B? N bond in soft scorpionates, which has implications for their use in more advanced chemistry.     

Computer simulation of proton channelling in beryllium

The channelling of protons through a thin beryllium crystal is simulated in a computer. The angular dependence of the momentum density is computed using particle trajectory approximation and is reported as the transmission spectra. In obtaining the spectra, the energy loss suffered by protons due to electron multiple scattering is considered and the effect of thermal vibrations treated separately. The spectra obtained are characteristic of the hcp structure of Be. Positions of the major dips in the transmission spectra are found to correlate well with the directions of neighbouring strings. Variations in the angle of incidence of the beam and in its initial azimuthal angle bring about modifications in the spectra depending on the transverse kinetic energy of the incident particles and the crystalline structure of Be. Thermal vibration of the lattice does not modify the spectra appreciably.