The interaction of morpholine with metal ions—I: Copper complexes

The synthesis and electronic and IR spectra of CuL₂(NO₃)₂ and CuL₄(NO₃)₂, where L stands for morpholine, are described. The thermal behaviour of the complexes is also discussed. The solids contain distorted octahedral Cu(II) bonded to morpholine through nitrogen only. In aqueous solutions only the species CuL₃(aq)²⁺ is stable in the concentration range 0.5 < [L] < 2 mol dm^?3, its stability constant being log K₃ = 14.64 ± 0.15 at 25.00°C and ionic strength 1 mol dm^?3; at very high morpholine concentrations, 3.4 < [L] < 6 mol dm^?3, evidence is also found for CuL₄(aq)²⁺, the value log K₄ = 15.5 being estimated. The aggressiveness of morpholine-H₂O₂ towards metallic copper is compared with that of ammonia-H₂O₂, both on thermodynamics and kinetics grounds; experimental results seems to be dominated by kinetics factors. The relevance of these results to water treatment in secondary systems of nuclear power reactors is discussed.     

Combustion synthesis and characterization of nanocrystalline WO3

The energy payback time associated with the semiconductor active material is an important parameter in a photovoltaic solar cell device. Thus lowering the energy requirements for the semiconductor synthesis step or making it more energy-efficient is critical toward making the overall device economics more competitive relative to other nonpolluting energy options. In this communication, combustion synthesis is demonstrated to be a versatile and energy-efficient method for preparing inorganic oxide semiconductors such as tungsten trioxide (WO3) for photovoltaic or photocatalytic solar energy conversion. The energy efficiency of combustion synthesis accrues from the fact that high process temperatures are self-sustained by the exothermicity of the combustion process, and the only external thermal energy input needed is for dehydration of the fuel/oxidizer precursor mixture and bringing it to ignition. Importantly, we show that, in this approach, it is also possible to tune the optical characteristics of the oxide semiconductor (i.e., shift its response toward the visible range of the electromagnetic spectrum) in situ by doping the host semiconductor during the formative stage itself. As a bonus, the resultant material shows enhanced surface properties such as markedly improved organic dye uptake relative to benchmark samples obtained from commercial sources. Finally, this synthesis approach requires only very simple equipment, a feature that it shares with other "mild" inorganic semiconductor synthesis routes such as sol-gel chemistry, chemical bath deposition, and electrodeposition. The present study constitutes the first use of combustion synthesis for preparing WO3 powder comprising nanosized particles.     

Molecular dynamics study of triosephosphate isomerase from Trypanosoma cruzi in water/decane mixtures

A comprehensive study of the triosephosphate isomerase from the parasite Trypanosoma cruzi (TcTIM) in water, in decane, and in three water/decane mixtures was performed using molecular dynamics (MD) simulations in a time scale of 40 ns. The structure and dynamics of the enzyme, as well as the solvent molecules' distribution and mobility, were analyzed in detail. In the presence of decane, the amplitudes of the most important internal motions of the enzyme backbone were observed to depend on the solvent concentration: the higher the water concentration, the greater the amplitudes. Contrary to this trend, the amplitudes of the TcTIM motions in pure water were similar to those of the simulation with the lowest water concentration. The enzyme was observed to be almost motionless in pure decane due to a sharp increase of the number of intramolecular hydrogen bonds. This caused a contraction of the enzyme structure accompanied by a loss of secondary structure and of a decrease of the hydrophilic solvent accessible surface. A similar behavior, although to a lesser extent, was observed in the simulation at the lowest water concentration. Our results suggest that the presence of decane molecules located at specific sites of the enzyme might accelerate its internal movements, although a minimum number of water molecules is needed for the protein to keep its structure and dynamics. Altogether, this work provides new insight into protein and water behavior in organic solvents as well as into the dynamics of TcTIM itself.     

Synthesis of 1,3‐oxazole and benzimidazole pendant groups from polyacrylonitrile hydrolysis products

New terpolymers containing heterocyclic pendant groups, such as 1,3 oxazole and benzimidazole are obtained by hydrolysis of polyacrylonitrile (PAN). These materials are spectroscopically characterized and their solubility, viscosity and thermal behavior are analyzed.     

Effect of vacuum annealing on the surface chemistry of electrodeposited copper(I) oxide layers as probed by positron annihilation induced auger electron spectroscopy

Vacuum anneal induced changes in the surface layers of electrodeposited copper(I) oxide (Cu2O) were probed by time-of-flight positron annihilation induced Auger electron spectroscopy (TOF-PAES) and by electron induced Auger electron spectroscopy (EAES). Large changes in the intensity of the Cu PAES intensity resulting from isochronal in situ vacuum anneals made at increasing temperatures indicated that, before thermal treatment, the surface was completely covered by a carbonaceous overlayer and that this layer was removed, starting at a temperature between 100 and 200 degrees C, to expose an increasing amount of Cu in the top layer as the anneal temperature was increased. The thickness of this overlayer was estimated to be approximately 4 A based on analysis of the EAES data, and its variation with the thermal anneal temperature was mapped. This study demonstrated the order-of-magnitude enhancement in the sensitivity of PAES to the topmost surface layer in Cu2O relative to the EAES counterpart; factors underlying this contrast are discussed. Finally, the implications of ultrathin carbon layers on semiconductor surfaces are discussed.     

Synthesis and NMR analysis of spiranic heterocycles from carbohydrate derivatives

We report the synthesis of some furanose and pyranose acylhydrazones and their heterocyclization products. The new compounds were characterized physically and spectroscopically and the syn‐anti and (R)‐(S) configuration was determined by NOESY experiments. We discuss the influence of the nucleophile, the temperature and the precursor structure on the heterocyclization products.     

Synthesis and characterization of a metal complex containing naringin and Cu, and its antioxidant, antimicrobial, antiinflammatory and tumor cell cytotoxicity

The antioxidant activity of flavonoids is believed to increase when they are coordinated with transition metal ions. However, the literature on this subject is contradictory and the outcome seems to largely depend on the experimental conditions. In order to understand the contribution of the metal coordination and the type of interaction between a flavonoid and the metal ion, in this study a new metal complex of Cu (II) with naringin was synthesized and characterized by FT-IR, UV-VIS, mass spectrometry (ESI-MS/MS), elemental analysis and 1H-NMR. The results of these analyses indicate that the complex has a Cu (II) ion coordinated via positions 4 and 5 of the flavonoid. The antioxidant, anti-inflammatory and antimicrobial activities of this complex were studied and compared with the activity of free naringin. The Naringin-Cu (II) complex 1 showed higher antioxidant, anti-inflammatory and tumor cell cytotoxicity activities than free naringin without reducing cell viability.     

Laboratory and field experiments used to identify<Emphasis Type="Italic"> Canis lupus</Emphasis> var. <Emphasis Type="Italic">familiaris</Emphasis> active odor signature chemicals from drugs,explosives, and humans

This paper describes the use of headspace solid-phase microextraction (SPME) combined with gas chromatography to identify the signature odors that law enforcement-certified detector dogs alert to when searching for drugs, explosives, and humans. Background information is provided on the many types of detector dog available and specific samples highlighted in this paper are the drugs cocaine and 3,4-methylenedioxy-N-methylamphetamine (MDMA or Ecstasy), the explosives TNT and C4, and human remains. Studies include the analysis and identification of the headspace "fingerprint" of a variety of samples, followed by completion of double-blind dog trials of the individual components in an attempt to isolate and understand the target compounds that dogs alert to. SPME–GC/MS has been demonstrated to have a unique capability for the extraction of volatiles from the headspace of forensic specimens including drugs and explosives and shows great potential to aid in the investigation and understanding of the complicated process of canine odor detection. Major variables evaluated for the headspace SPME included fiber chemistry and a variety of sampling times ranging from several hours to several seconds and the resultant effect on ratios of isolated volatile components. For the drug odor studies, the CW/DVB and PDMS SPME fibers proved to be the optimal fiber types. For explosives, the results demonstrated that the best fibers in field and laboratory applications were PDMS and CW/DVB, respectively. Gas chromatography with electron capture detector (GC/ECD) and mass spectrometry (GC/MS) was better for analysis of nitromethane and TNT odors, and C-4 odors, respectively. Field studies with detector dogs have demonstrated possible candidates for new pseudo scents as well as the potential use of controlled permeation devices as non-hazardous training aids providing consistent permeation of target odors.     

Influence of pH on the photochemical and electrochemical reduction of the dinuclear ruthenium complex, [(phen)2Ru(tatpp)Ru(phen)2)Cl4, in water: proton-coupled sequential and concerted multi-electron reduction

The dinuclear ruthenium complex [(phen)2Ru(tatpp)Ru(phen)2]4+ (P; in which phen is 1,10-phenanthroline and tatpp is 9,11,20,22-tetraaza tetrapyrido[3,2-a:2'3'-c:3',2'-l:2',3']-pentacene) undergoes a photodriven two-electron reduction in aqueous solution, thus storing light energy as chemical potential within its structure. The mechanism of this reduction is strongly influenced by the pH, in that basic conditions favor a sequential process involving two one-electron reductions and neutral or slightly acidic conditions favor a proton-coupled, bielectronic process. In this complex, the central tatpp ligand is the site of electron storage and protonation of the central aza nitrogen atoms in the reduced products is observed as a function of the solution pH. The reduction mechanism and characterization of the rich array of products were determined by using a combination of cyclic and AC voltammetry along with UV-visible reflectance spectroelectrochemistry experiments. Both the reduction and protonation state of P could be followed as a function of pH and potential. From these data, estimates of the various reduced species' pKa values were obtained and the mechanism to form the doubly reduced, doubly protonated complex, [(phen)2Ru(H2tatpp)Ru(phen)2]4+ (H2P) at low pH (< or =7) could be shown to be a two-proton, two-electron process. Importantly, H2P is also formed in the photochemical reaction with sacrificial reducing agents, albeit at reduced yields relative to those at higher pH.