Biotransformation of two furanocoumarins by the fungi species Aspergillus sp. PTCC 5266 and Aspergillus niger PTCC 5010

The microbial transformations of peucedanin and oreoselon by the fungi Aspergillus niger and Aspergillus sp. were investigated for the first time. Incubation of peucedanin with A. niger yielded a new hydroxylated metabolite with high yield (56%), which was characterized as 2-(1-hydroxypropan-2-yl)-3-methoxy-7H-furo[3,2-g]chromen-7-one. Oreoselon was converted to a new reduced metabolite methyl 3-(2,3-dihydro-6-hydroxy-2-isopropyl-3-oxobenzofuran-5-yl)propanoate in biotransformation by Aspergillus sp. The structures of the metabolites were determined by spectroscopic methods including IR, EI-MS, ¹H NMR, ¹³C NMR, and elemental analysis.     

Suzuki–Miyaura coupling catalyzed by palladium nanoparticles biosynthesized using Glycyrrhiza glabra as reducing and stabilyzing agent

An unprecedented environmentally friendly method has been developed for the synthesis of palladium nanoparticles supported on Glycyrrhiza glabra. The synthesized nanoparticles were utilized in Suzuki–Miyaura reaction between different aryl halides and aryl bronic acid in aqueous media. This heterogeneous catalyst can be reused and recycled repeatedly more than five times with only slight loss of its initial catalytic efficiency. This reaction carrid out under atmospheric pressure with high efficiency, unique and simple work‐up procedure and excellent yields.     

Green and effective route for the synthesis of monodispersed palladium nanoparticles using herbal tea extract (Stachys lavandulifolia) as reductant,stabilizer and capping agent,and their application as homogeneous and reusable catalyst in Suzuki coupling reactions in water

A simple and eco‐friendly procedure has been devised for the green synthesis of palladium nanoparticles, using the aqueous extract of herbal tea (Stachys lavandulifolia), a renewable and nontoxic natural phyto‐exudate. The water‐soluble components of the extract act as reducing agent and stabilizer. This green route does not require a surfactant or capping agent for the growth of palladium nanoparticles. The generated nanoparticles were analysed using UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray analysis and inductively coupled plasma. The palladium nanoparticles having spherical shape and dimensions of between 5 and 7 nm were employed as a homogeneous catalyst for Suzuki coupling reactions conducted in water under mild conditions. Good yields of products, a facile work‐up, no evidence of leached palladium from the catalyst surface and smooth recovery of the catalysis by adding ethyl acetate, which could be reused at least eight times, confirm the very good efficiency of the catalytic reaction. Copyright © 2014 John Wiley & Sons, Ltd.     

Cobalt(I)-catalyzed cocyclotrimerization of acetylene with 2,6-dicyanopyridines

A procedure of general application to the synthesis of alkyl-substituted 2-cyano-6-(2-pyridyl)pyridines from alkylpyridines is outlined.     

Potential of Modified Multiwalled Carbon Nanotubes with 1-(2-Pyridylazo)-2-naphtol as a New Solid Sorbent for the Preconcentration of Trace Amounts of Cobalt(II) Ion

The present paper reports on the application of modified multiwalled carbon nanotubes (MMWCNTs) as a new, easily prepared and stable solid sorbent for the preconcentration of trace Co(II) in aqueous solution. Multiwalled carbon nanotubes (MWCNTs) were oxidized with concentrated HNO(3) and modified with 1-(2-pyridylazo)-2-naphtol (PAN), and were then used as a solid phase for the preconcentration of Co(II). Factors influencing the sorption and desorption of Co(II) were investigated. Elution was carried out with 0.5 mol L(-1) HNO(3). The amount of eluted Co(II) was measured using flame atomic absorption spectrometry. The effects of the experimental parameters, including the sample pH, sample flow rate, eluent flow rate and eluent concentration, were investigated. The effect of coexisting ions showed no interference from most ions tested. The proposed method permitted a large enrichment factor (about 300). The precision of the method was 1.63% (for eight replicate determination of 0.5 microg mL(-1) of Co(II)) and the limit of detection was 0.55 ng mL(-1). The method was applied to the determination of Co(II) in water, biological and standard samples.     

NMR and INDO study of the Ni(II) complexes of maleic and succinic acids

A new approach to investigate the conformational properties of the Ni(II) complexes of maleic and succinic acids is reported. The use of C-13 and H-1 paramagnetic shifts and relaxation rates together with an INDO analysis on suitable radical models of the ligands proved a powerful tool in elucidating the conformation of the Ni(II) complex with the partially rigid maleic acid.     

C-13 magnetic relaxation rates and H-1 and C-13 paramagnetic shifts of Ni(II) complex of dopamine

The ¹H and ¹³C isotropic contact shifts and the ¹³C relaxation times of dopamine in aqueous solution have been measured in the presence of the Ni(II) ion. The pD dependence of the ¹H and ¹³C paramagnetic shifts was also investigated. From the analysis of the shifts at pD = 6.5 and from the INDO MO calculations on selected models of dopamine radicals, a dominant σ delocalization mechanism of the spin density is proposed. From the spin distribution on the ligand carbon atoms, the metal centered as well as the ligand centered dipolar contributions of the modified Solomon—Bloembergen equation were calculated and an estimate of the correlation time τ_c was given.     

Directed assembly of single-walled carbon nanotubes via drop-casting onto a UV-patterned photosensitive monolayer

We report the use of a novel UV-sensitive self-assembled monolayer to selectively deposit single-walled carbon nanotubes from solution using heterogeneous surface wettability. This process combines ubiquitous photopatterning techniques with simple solution processing to yield highly selective and densely packed carbon nanotube patterns. The essential concept behind this process is the change in surface chemistry caused by the UV-induced monolayer reaction. Selective deposition of carbon nanotubes was achieved by drop-casting, and the resulting films show local ordering, indicating that further development of this process will lead to simple technique for large-scale integration.