Emission Spectrum and Resistivity of Low Power Plasma Weld Arcs

Emission spectra from plasma arc welds were observed under a variety of current, voltage, polarity, and standoffs. If reverse polarity (welding torch positive) welds are struck below 50 amperes most of the power is deposited at the electrode rather than the workpiece because of low carrier density within the arc. Straight polarity, on the other hand, suffers no such limitation because of electrons created in the pilot arc used to start the weld process.     

Expanded Ligands Based upon Iron(II) Coordination Compounds of Asymmetrical Bis(terpyridine) Domains

The synthesis and characterization of two tritopic ligands containing a 2,2′:6′,2″-terpyridine (tpy) metal binding domain and either a 3,2′:6′,3″- or a 4,2′:6′,4″-tpy domain are detailed. The synthetic routes to these ligands involved the [Pd(dppf)Cl₂]-catalyzed coupling of a boronic ester-functionalized 2,2′:6′,2″-tpy with bromo-derivatives of 3,2′:6′,3″-tpy or 4,2′:6′,4″-tpy. The 2,2′:6′,2″-tpy domains of the tritopic ligands preferentially bind Fe²⁺ in reactions with iron(II) salts leading to the formation of two homoleptic iron(II) complexes containing two peripheral 3,2′:6′,3″-tpy or 4,2′:6′,4″-tpy metal-binding sites, respectively. These iron(II) complexes are potentially tetratopic ligands and represent expanded versions of tetra(pyridin-4-yl)pyrazine.     

Synthesis of Stereochemically Flexible Cyclic Biphenylbisphosphinite Ligands: Control of the Dynamics and Selectivity

Novel l -tartaric acid based stereodynamic biphenylbisphosphinite ligands with anilino linkers were prepared as cyclic diamide compounds. The influence of the constitutional substitution pattern of the amino group at the aniline moiety on the diastereoselective formation of the ligand was investigated. While the meta-anilino bridged ligands showed a highly dynamic behavior and no discrimination between (R_ax) and (S_ax) configuration, l -tartaric acid substitution on ortho-anilino bridged ligands leads to diastereoselective self-alignment of the central biphenol axis, which controls the stereoselectivity of the ligand and catalyst. The experimental findings were corroborated by theoretical calculations. In the rhodium-catalyzed enantioselective hydrogenation of methyl 2-acetamidoacrylate (MAA), an enantiomeric ratio of 75 : 25 (R/S) was obtained for the ortho-substituted ligand.     

α-Diimine Cisplatin Derivatives: Synthesis,Structure, Cyclic Voltammetry and Cytotoxicity

Three new Pt(II) complexes [(dpp-DAD)PtCl₂] (I), [(Mes-DAD(Me)₂)PtCl₂] (II) and [(dpp-DAD(Me)₂)PtCl₂] (III) were synthesized by the direct reaction of [(CH₃CN)₂PtCl₂] and corresponding redox-active 1,4-diaza-1,3-butadienes (DAD). The compounds were isolated in a single crystal form and their molecular structures were determined by X-ray diffraction. The purity of the complexes and their stability in solution was confirmed by NMR analysis. The Pt(II) ions in all compounds are in a square planar environment. The electrochemical reduction of complexes I–III proceeds in two successive cathodic stages. The first quasi-reversible reduction leads to the relatively stable monoanionic complexes; the second cathodic stage is irreversible. The coordination of 1,4-diaza-1,3-butadienes ligands with PtCl₂ increases the reduction potential and the electron acceptor ability of the DAD ligands. The synthesized compounds were tested in relation to an adenocarcinoma of the ovary (SKOV3).     

A Computer Simulation Insight into the Formation of Apocarotenoids: Study of the Carotenoid Oxygenases BCO1 and BCO2 and Their Interaction with Putative Substrates

Carotenoids are isoprenoid pigments, and sources of vitamin A in humans. The first metabolic pathway for their synthesis is mediated by the enzymes β,β-carotene-15,15′-dioxygenase (BCO1) and β,β-carotene-9′,10′-dioxygenase (BCO2), which cleave carotenoids into smaller compounds, called apocarotenoids. The objective of this study is to gain insight into the interaction of BCO1 and BCO2 with carotenoids, adding structural diversity and importance in the agro-food and/or health sectors. Homology modeling of BCO1 and BCO2, and the molecular dynamics of complexes with all carotenoids were performed. Interaction energy and structures were analyzed. For both enzymes, the general structure is conserved with a seven beta-sheet structure, and the β-carotene is positioned at an optimal distance from the catalytic center. Fe²⁺ forms in an octahedral coordination sphere with four perfectly conserved histidine residues. BCO1 finds stability in a structure in which the β-carotene is positioned ready for enzymatic catalysis at the 15–15′ bond, and BCO2 in positioning the bond to be cleaved (C9–C10) close to the active site. In BCO1 the carotenoids interact with only seven residues with aromatic rings, while the interaction of BCO2 is much more varied in terms of the type of interaction, with more residues of different chemical natures.     

Ionic Dioxidovanadium(V) Complexes with Schiff-Base Ligands as Potential Insulin-Mimetic Agents—Substituent Effect on Structure and Stability

Four dioxidovanadium(V) complexes with Schiff-base ligands based on 2-hydroxybenzhydrazide with four different substituted salicylaldehydes (5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde, 5-nitrosalicylaldehyde, 3-bromo-5-chlorosalicylaldehyde) were synthesized and described, by using V₂O₅ and triethylamine. The single crystal X-ray structure measurements as well as elemental analyses and IR spectra confirmed the formulas of the ionic complexes with a protonated triethylamine acting as counterion, HTEA[VO₂(L)] (HL = Schiff-base ligand). The kinetic stability of the complexes at pH = 2 and 7 was discussed with respect to the neutral vanadium(V) complexes previously studied as potential insulin-mimetic agents. A correlation between the substituents in an aromatic ring of the Schiff-base ligands with crystal packing, and also with the stability of the compounds, was presented.     

Organic/Inorganic Species Synergistically Supported Unprecedented Vanadomolybdates

Vanadomolybdates (VMos), comprised of Mo and V in high valences with O bridges, are one of the most important types of polyoxometalates (POMs), which have high activity due to their strong capabilities of gaining/losing electrons. Compared with other POMs, the preparation of VMos is difficult due to their relatively low structural stability, especially those with unclassical architectures. To overcome this shortcoming, in this study, triol ligands were applied to synthesize VMos through a beaker reaction in the presence of V₂O₅, Na₂MoO₄, and organic species in the aqueous solution. The single-crystal X-ray diffraction results indicate that two VMo clusters, Na₄{V₅Mo₂O₁₉[CH₃C(CH₂O)₃]}∙13H₂O and Na₄{V₅Mo₂O₁₉[CH₃CH₂C(CH₂O)₃]}∙13H₂O, with a similar architecture, were synthesized, which were both stabilized by triol ligand and {MoO₆} polyhedron. Both clusters are composed of five V ions and one Mo ion in a classical Lindqvist arrangement with an additional Mo ion, showing an unprecedented hepta-nuclear VMo structure. The counter Na⁺ cations assemble into one-dimensional channels, which facilitates the transport of protons and was further confirmed by proton conductivity experiments. The present results provide a new strategy to prepare and stabilize VMos, which is applicable for developing other compounds, especially those with untraditional architectures.     

Structure–Activity Relationship Development Efforts towards Peripherally Selective Analogs of the Cannabinoid Receptor Partial Agonist BAY 59-3074

Selective modulation of peripheral cannabinoid receptors (CBRs) has potential therapeutic applications in medical conditions, including obesity, diabetes, liver diseases, GI disorders and pain. While there have been considerable efforts to produce selective antagonists or full agonists of CBRs, there has been limited reports on the development of partial agonists. Partial agonists targeting peripheral CBRs may have desirable pharmacological profiles while not producing centrally mediated dissociative effects. Bayer reported that BAY 59-3074 is a CNS penetrant partial agonist of both CB1 and CB2 receptors with efficacy in rat models of neuropathic and inflammatory pain. In this report, we demonstrate our efforts to synthesize analogs that would favor peripheral selectivity, while maintaining partial agonism of CB1. Our efforts led to the identification of a novel compound, which is a partial agonist of the human CB1 (hCB1) receptor with vastly diminished brain exposure compared to BAY 59-3074.