SAPO-5 and SAPO-11: Synthesis, characterization and camphene isomerization activity

SAPO-5 and SAPO-11 were synthesized using aluminium isopropoxide and tetraethyl orthosilicate as source materials for aluminium and silicon, respectively, adopting a modified procedure. The as-synthesized materials were characterized by XRD and chemical analysis. Acidity was found by temperature-programmed desorption using TGA. Unit cell parameters were calculated for both as-synthesized and calcined materials. The catalytic activity of SAPO-5 and SAPO-11 in camphene isomerization was studied and selective formation of tricyclene was achieved.     

FT-EPR with a Nonresonant Probe: Use of a Truncated Coaxial Line

A truncated transmission line probe (TLP) has been utilized to excite and detect time domain responses after pulsed excitation in electron paramagnetic resonance (EPR) spectroscopic experiments in the frequency range 200–400 MHz. The TLP device is a modified short-circuited coaxial line, which allows the irradiation of the sample by the traveling waveB₁fields in the frequency range of kilohertz to 30 GHz. In EPR studies at 300 MHz carrier frequency, with 10 W incident power, a 45° pulse is 45 ns in duration. This corresponds to a 0.9-GB₁field. Using the TLP, time-domain responses from the solidN-methyl pyridiniumtetra-cyanoquinodimethane (TCNQ) were collected at 200, 250, 300, and 350 MHz, with the range limited by the amplifiers. In addition two tubes containing TCNQ placed side-by-side vertically along the axis of the probe were used to collect time domain responses in the presence of magnetic field gradients to test the feasibility of two-dimensional imaging using a TLP. The magnetic field gradient was steered in thexzplane and 36 projections were collected at 5° intervals. Using filtered back-projection image reconstruction, the two-dimensional spatial image in thexzplane was obtained at good resolution.     

Single crystal EPR of Cu(C5H5NO)6(BF4)2: an example of admixed ground state

Single crystal electron paramagnetic resonance (EPR) of Cu(C5H5NO)6(BF4)2 is studied at 300 K. The spin Hamiltonian parameters obtained at 300 K are A11 = -149.8, A22 = -50.7 and A33 = -37.7 (all in units of 10(-4) cm(-1)), g11 = 2.3452, g22 = 2.0679 and g33 = 2.0695. Angular variation of hyperfine structure lines shows the presence of a single magnetic site. The low magnitude of the A11 value for Cu(C5H5NO)6(BF4)2 is rationalized in terms of a mixed d(x2-y2)/d(z2) ground state.     

A biogenetically patterned conversion of palmatine into polycarpine

Oxidation of palmatine ($\text{1}$) choride with $\text{m}$-chloroperbenzoic acid in methylene chloride in the presence of sodium bicarbonate at near ?78° C yields polycarpine ($\text{2}$). A new biogenetic route to the aporphines is proposed which does not involve phenolic oxidative coupling, and proceeds through the intermediacy of protoberberinium salts.     

Extracellular matrix-like surfactant polymers containing arginine-glycine-aspartic acid (RGD) peptides

We report on a novel series of biomimetic polymers exhibiting interfacial properties similar to the extracellular matrix. A series of well-defined surfactant polymers were synthesized by simultaneously incorporating arginine-glycine-aspartic acid (RGD) peptide, dextran oligosaccharide, and hexyl ligands with controlled feed ratios onto a poly(vinyl amine) (PVAm) backbone. The peptide sequence was H-GSSSGRGDSPA-NH(2) (Pep) having a hydrophilic extender at the amino terminus and capped carboxy terminus. The peptide-to-dextran (Pep:Dex) ratios were varied to create surfactants having 0, 25, 50, 75, and 100 mol-% peptide relative to dextran. The surfactants were characterized by IR, NMR and atomic force microscopy (AFM) for composition and surface active properties. AFM confirmed full surface coverage of PVAm(Pep)(100%) on graphite, and supported the mechanism of interdigitation of hexyl ligands between surfactant molecules within a specified range of hexyl chain densities. the attachment and growth of human pulmonary artery endothelial cells on the PVAm(Pep)(100%) surface was identical to the fibronectin positive control. Cell adhesion decreased dramatically with decreasing peptide density on the surfactant polymers. Molecular model of a peptide surfactant polymer, consisting of poly(vinyl amine) backbone with peptide, dextran oligosaccharide and hexyl branches coupled to the polymer chain.     

Cosmological models with particle creation and bulk viscosity

The effect of bulk viscosity on the evolution of the Friedmann models is investigated in the context of open thermodynamic systems, which allows for particle creation. It is seen that, by choosing an appropriate function,(t), for the particle creation, all the models presented exhibit inflationary expansion and a non-singular beginning.     

In situ generation of polyaniline in poly(dimethylsiloxane) networks

Polyaniline (PANI) is one of the most studied and most stable electrically conductive polymers, with the conductive form being the navy blue emeraldine salt. However, PANI is very difficult to process and displays poor mechanical performance, which suggests improving its properties by developing composite systems. In the present approach, PANI was generated in situ in poly(dimethylsiloxane) (PDMS) networks. The color of the composites varied from brown, to blue, to greenish blue, with the blue samples being the most conductive. The chemical structures of the samples were studied using FT-IR/ATR spectroscopy, which confirmed that there was more conjugation in the more conductive samples.This paper is dedicated to Mike Owen on occasion of his winning the DeBruyn medal, the first silicon chemist to do so.     

Reusable Nickel Nanoparticles‐Catalyzed Reductive Amination for Selective Synthesis of Primary Amines

The preparation of nickel nanoparticles as efficient reductive amination catalysts by pyrolysis of in situ generated Ni‐tartaric acid complex on silica is presented. The resulting stable and reusable Ni‐nanocatalyst enables the synthesis of functionalized and structurally diverse primary benzylic, heterocyclic and aliphatic amines starting from inexpensive and readily available carbonyl compounds and ammonia in presence of molecular hydrogen. Applying this Ni‐based amination protocol, ‐NH₂ moiety can be introduced in structurally complex compounds, for example, steroid derivatives and pharmaceuticals.