Well parameters of two‐dimensional electron gas in Al0.88In0.12N/AlN/GaN/AlN heterostructures grown by MOCVD

Resistivity and Hall effect measurements were carried out as a function of magnetic field (0‐1.5 T) and temperature (30‐300 K) for Al_0.88In_0.12N/AlN/GaN/AlN heterostructures grown by Metal Organic Chemical Vapor Deposition (MOCVD). Magnetic field dependent Hall data were analyzed by using the quantitative mobility spectrum analysis (QMSA). A two‐dimensional electron gas (2DEG) channel located at the Al_0.88In_0.12N/GaN interface with an AlN interlayer and a two‐dimensional hole gas (2DHG) channel located at the GaN/AlN interface were determined for Al_0.88In_0.12N/AlN/GaN/AlN heterostructures. The interface parameters, such as quantum well width, the deformation potential constant and correlation length as well as the dominant scattering mechanisms for the Al_0.88In_0.12N/GaN interface with an AlN interlayer were determined from scattering analyses based on the exact 2DEG carrier density and mobility obtained with QMSA. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Novel bioactive vic-dioxime ligand containing piperazine moiety: Synthesis,X-ray crystallographic studies, 2D NMR applications and complexation with Ni(II)

A new vic-dioxime ligand bearing an important pharmacophore substituent, anti-1-(4-benzylpiperazine-1-yl) phenylglyoxime (LH₂) (Scheme 1), has been synthesized and its nickel(II) complex was obtained by the reaction of NiCl₂·6H₂O and the ligand. The characterization of the newly formed compounds was performed by elemental analysis, FT-IR, 1D NMR (¹H, ¹³C, DEPT), 2D NMR (HMBC), ESI mass-spectrometry, TG/DTA, X-ray crystallography. The antibacterial activity was also studied against Staphylococcus aureus ATCC 25923, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Lactobacillus acidophilus RSHM 06029, Escherichia coli ATCC 25922, E. coli ATCC 35218, Pseudomonasaeruginosa ATCC 27853. The antimicrobial test results indicated that all the compounds have mild antibacterial activity against both Gram negative and Gram positive bacterial species.     

New types of self-organizing interfacial alginate membranes

In this publication we describe a new self-association process, which leads to the formation of ultra-thin alginate layers at the interface between oil and water. The water phase contains a highly dilute solution of sodium alginate. These macromolecules are negatively charged and they are not surface active. The oil phase contains a small concentration of positively charged surfactants. At the interface between oil and water, the cationic surfactants tend to form complexes with the negatively charged alginate polyelectrolytes in the aqueous solutions. This leads to striking adsorption processes of the solved polysaccharide molecules at the oil-water interface. Upon the addition of calcium ions, a cross-linking process sets in and one obtains the thin viscoelastic membranes, which are anchored at the interface between oil and water. The thickness of these membranes is of the order of 0.2 mm. Similar structures can also be formed by solving positively charged Gemini surfactants in the oil phase. In this case, the cationic surfactant molecules induce the adsorption processes of alginate macromolecules, and they also act as cross-linking compounds. In a series of experiments, we measured the surface rheological properties of these ultra-thin alginate membranes. The results of these investigations point to the presence of electrostatically stabilized membranes. Special interest was given to the influence of the guluronate content of the alginates, which is important for the cross-linking mechanism according to the egg-box model. Finally, this article finishes with the discussion of the proposed building mechanisms of these membranes.     

Cationic gemini surfactants as pseudostationary phases in micellar electrokinetic chromatography. Part I: Effect of head group

Two cationic gemini surfactants with pyrrolidinium or alkyl ammonium head groups with but-2-yne spacers, but with the same length hydrocarbon chain have been characterized with respect to their aggregation behaviors and separation power as pseudostationary phases (PSPs) for micellar electrokinetic chromatography (MEKC). They were compared with a commonly used PSP, sodium dodecylsulfate (SDS). The results suggest that the head groups of the surfactants have some effect on physicochemical properties such as critical micelle concentration (CMC), C₂₀, γ_CMC, partial specific volume, methylene selectivity and mobilities of the surfactants. CMC values of G1, G2 and SDS in pure water were found to be 0.82, 0.71, and 8.08 mM, respectively; they were reduced to 0.21, 0.11, and 3.0 mM when measured in 10 mM phosphate buffer at pH 7.0. G1 (α_CH2=2.74${\alpha }_{\text{C}{\text{H}}_2}=2.74$) and G2 (α_CH2=2.48${\alpha }_{\text{C}{\text{H}}_2}=2.48$) provided the most and the least hydrophobic environment, respectively. According to their partial specific volumes, geminis were found to have more flexible structures as compared with sodium dodecylsulfate. The effects of the head group structure were also characterized with the linear solvation energy relationship (LSER) model, which was able to evaluate the role of solute size, polarity/polarizability, and hydrogen bonding on retention and selectivity. The cohesiveness, hydrogen bond acidic and basic character of the surfactant systems were found to have the most significant influence on selectivity and MEKC retention of the gemini surfactants. It should be noted that with their large positive coefficient a values, G1 and G2 were found to be stronger HB acceptors than anionic and most of the cationic surfactants studied in the literature.     

Charge transfer complex formation between p-chloranil and 1,n-di(9-anthryl)alkanes

Dimer model compounds of polyvinylanthracenes (1,n-di(9-anthryl)alkanes, when n=1-5) were synthesized to model the effects of distance and orientation between anthracene groups in polymeric systems. Charge transfer (CT) complexes of anthracene, 9-methylanthracene and 1,n-di(9-anthryl)alkanes with p-chloranil (p-CHL) have been investigated spectrophotometrically in dichloromethane. The colored products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptor. The formation constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters were calculated by Van't Hoff equation. Stochiometries of the complexes formed between donors and acceptor were defined by the Job's method of the continuous variation and found in 1:1 complexation with donor and acceptor at the maximum absorption bands.     

Charge transfer complex studies between some non-steroidal anti-inflammatory drugs and pi-electron acceptors

Charge transfer (CT) complexes of some non-steroidal anti-inflammatory drugs, naproxen and etodolac which are electron donors with some pi-acceptors, such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranil (p-CHL), have been investigated spectrophotometrically in chloroform at 21 degrees C. The coloured products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptors. Beer's law is obeyed and colours were produced in non-aqueous media. All complexes were stable at least 2 h except for etodolac with DDQ stable for 5 min. The equilibrium constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters DeltaH, DeltaS, DeltaG degrees were calculated by Van't Hoff equation. Stochiometries of the complexes formed between donors and acceptors were defined by the Job's method of the continuous variation and found in 1:1 complexation with donor and acceptor at the maximum absorption bands in all cases.     

Enantioselective transfer hydrogenation of pro-chiral ketones catalyzed by novel ruthenium and iridium complexes of well-designed phosphinite ligand

Abstract

The interaction of [Ru(η⁶-arene)(μ-Cl)Cl]₂ and Ir(η⁵-C₅Me₅)(μ-Cl)Cl]₂ with a new Ionic Liquid-based phosphinite ligand, [(Ph₂PO)-C₆H₉N₂Ph]Cl, (2) gave [Ru((Ph₂PO)-C₆H₉N₂Ph)(η⁶-p-cymene)Cl₂]Cl (3), [Ru((Ph₂PO)-C₆H₉N₂Ph)(benzene)Cl₂]Cl (4) and [Ir((Ph₂PO)-C₆H₉N₂Ph)(C₅Me₅)Cl₂]Cl (5), complexes. All the compounds were characterized by a combination of multinuclear NMR and IR spectroscopy as well as elemental analysis. Furthermore, the Ru(II) and Ir(III) catalysts were applied to asymmetric transfer hydrogenation of acetophenone derivatives using 2-propanol as a hydrogen source. The results showed that the corresponding alcohols could be obtained with good activity (up to 55% ee and 99% conversion) under mild conditions. Notably, [Ir((Ph₂PO)-C₆H₉N₂Ph)(C₅Me₅)Cl₂]Cl (5) is more active than the other analogous complexes in the transfer hydrogenation (up to 81% ee).     

Synthesis, characterization, and crystal structure of 1-(4-chloro-benzoyl)-3-naphthalen-1-yl-thiourea

1-(4-Chloro-benzoyl)-3-naphthalen-1-yl-thiourea has been synthesized and characterized by elemental analysis, IR spectroscopy, and mass spectrometry. The crystal and molecular structure of the title compound has been determined from single crystal X-ray diffraction data. It crystallizes in the triclinic space group P-1, with a = 6.962(1) Å, b = 10.770(3) Å, c = 11.738(2) Å, = 65.76(2)°, = 80.03(1)°, = 84.86(2)°, and D _calc= 1.432 g cm^–1 for Z = 2. The thermal behavior of the compound has been studied by DTA and TG. The antibacterial activities of the title compound were investigated for three Gram (+) and two Gram (–) bacteria by employing broth microdilution method and subsequently, inhibitory activity against yeast-like fungi was also determined.