Main Group Chemistry

Cocsuline, a biologically active natural product, is biosynthetically related to the more common bisbenzylisoquinoline alkaloids. We perform a comprehensive quantum chemical analysis on cocsuline using density functional theory at B3LYP/6-311G(d,p) level. The equilibrium molecular structure of cocsuline has been obtained. The weak intra-molecular C-H…O interaction is recognized, characterized and quantified by quantum theory of atoms in molecule (QTAIM). The chemical reactivity of cocsuline is explained and discussed with the help of HOMO, LUMO and MESP surfaces. The vibrational infrared spectrum of cocsuline has been calculated and prominent vibrational modes have been assigned. A good agreement between our calculated wavenumbers and experimentally reported values has been observed. The molecular docking of cocsuline into dihydrofolate reductase receptor shows that it may inhibits this enzyme and acts as an effective antimalarial drug.

We studied the adsorption of atomic and molecular hydrogen on an Mg₁₂O₁₂ nanotube with a different coverage by means of density functional calculations. We found that (1) an H atom prefers to be adsorbed on the top of an O atom of the tube surface rather than Mg atom; (2) 1, 2 addition of two H atoms to terminal Mg and O atoms is energetically more favorable than the addition to central atoms; (3) HOMO-LUMO energy gap of the tube dramatically decreases upon hydrogen adsorption only on oxygen atoms, transferring the intrinsic semiconductor tube to an extrinsic n-type semiconductor; (4) saturating the open end atoms with 12H atoms has no significant effect on the electronic properties of the tube; (5) upon adsorption of H on O atoms, the work function of the tube is considerably decreased, facilitating the field electron emission from the tube surface.

Human health is at risk due to exposure to mercury vapors that arise from breakage of compact fluorescent lamps (CFLs). Mercury content of CFLs, according to the United States Environmental Protection Agency (US EPA), varies from 2 to 5 mg with average value of 4 mg. If the amount of mercury exceeds this limit, it may be dangerous to the human health and these CFLs will fall into the hazardous waste category. Most of the currently available CFLs in the Saudia Arabia (S.A.) market are manufactured in China and by well-known, worldwide brands. To ensure the commitment of these companies to the US EPA regulations, total mercury content was determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Nineteen different types of CFLs were purchased from local stores and analyzed by ICP-MS. The surprising results was that most of the Chinese CFLs had values of mercury up to three times than the maximum limit recommended by US EPA. This study was devoted to highlight the risk factor that CFLs may have for public health.

xCsH₂PO₄·(1-x)Te(OH)₆ composites have been synthesized for the different compositions, x = 0.02, 0.04, 0.05, 0.06, 0.08 (labeled composites A-E). The composites were characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermogravimetry (TG) and Differential Thermal Analysis (DTA). Telluric acid, Te(OH)₆, added to cesium dihydrogen phosphate (CsH₂PO₄) significantly effects the structure, particle size and thermal stability of the composite material. Enhanced thermal stability could lead to use of CsH₂PO₄ as an electrolyte in low temperature fuel cells.

Dichlorodiphenyltrichloroethane (DDT), one of the persistant organic pollutants, was degraded by using nano-size zero valent iron (NZVI) and NZVI with Cu. The Box Behnken Design of Experiments was used to determine the effects of four factors: namely, initial DDT concentration (C_o), metal loading, % Cu (M), and pH of test solution, on the degradation of DDT. Experiments were conducted at room temperature. The response was expressed as mg DDT degraded per g of metal particles. Among four factors, the metal loading and initial DDT concentration were the most significant. Increasing the initial DDT concentration increased the amount of DDT degraded per unit amount of metal particles. According to the effect of metal loading, only a small amount of metal particles is necessary to effect DDT degradation. The degradation of DDT was different with NZVI alone and bimetallic NZVI/Cu. However, only the addition of Cu up to 5% of the total metal loading improved DDT degradation significantly. DDT degradation was the most favorable at pH 3 and the least was pH 2. The mg DDT degraded per g metal particles could be modeled by the equation R = 7.60 + 2.63C_o –4.2M + 1.21pH. The optimum DDT degradation condition was also observed.

The present investigation aimed to evaluate the antibacterial activity of marine macroalgae collected during winter and spring 2011 from the Red Sea of Jeddah, Saudi Arabia. The activity of petroleum ether, diethyl ether, ethyl acetate and methanol extract of algae belonging to Chlorophyta, Phaeophyta and Rhodophyta were examined against pathogenic bacteria. The crude extract of algae evoked several patterns of antibacterial activities. The petroleum ether extract of Gracilaria multipartita, Ulva reticulata and Sargassum marginatum collected in spring recorded the maximum inhibitory activity against Bacillus subtilis (14–25 mm), MRSA (24–35 mm) and Staphylococcus aureus (14–18 mm), respectively. However, Escherichia coli, Klebsiella pneumoniae were highly inhibited by petroleum ether extract of G. multipartita collected in spring (17–24 mm and 15–19 mm, respectively). Pseudomonas aeruginosa recorded the greatest zone of inhibition (18–22 mm) by the petroleum ether extract of S. marginatum gathered during winter. The MICs values for bacteria were ranged between 1.00–2.75 μg/ml. The chemical composition of the most effective algae extract against pathogenic bacteria was performed by GC-MS and ¹H-NMR analysis. The major components of extract were hydrocarbons, carotene derivatives, fatty acids and sterols. The present finding revealed that the tested algae can be used as possible natural source of antibacterial compounds.

The accumulation and factors affecting Poly 3-hydroxybutyric acid (PHB) production in cyanobacteria have not been clearly documented. In the present study, three PHB producers belonging to cyanobacteria were identified as Oscillatoria salina, Anabaena cylindrica and Nostoc linckia, based on their morphological features and microscopic observations. Their growth and PHB production after 7, 14 and 21 days in BG11 medium were determined. The highest dry weight for the isolates was observed at stationary phase (14 days) and PHB accumulation (%, w/w of dry cells) increased with increasing dry weight up to 14 days, then a decline was observed after 21 days. At the stationary phase, cells of O. salina, A. cylindrica and N. linckia accumulated PHB up to 13.62, 11.88 and 10.03% (w/w of dry cells), respectively. The pH values between 8 and 9 were preferred for PHB accumulation. O. salina, A. cylindrica and N. linckia accumulated the highest PHB 17.31, 15.22 and 14.95%, respectively at pH 8. Nitrogen and phosphorus starvation were found stimulatory for PHB accumulation and he highest PHB production was recorded for O. salina, 20.41 and 26.32%, respectively after 14 days of incubation. Electron microscopic analyses of O. salina cells showed the bioplastic accumulation in granule-like structures which was extracted and studied using IRFT analysis. In conclusion, cyanobacteria are capable of synthesizing high poly-β-hydroxybutyrate (PHB) under stress.

A group of organotin(IV) complexes with thiohydrazones derived from phenethylamine were synthesised in 1:1 complexes. The following organotin(IV) complexes have been synthesized: (C₆H₅CH₂)₂Sn(L¹)Cl₂, (p-ClC₆H₄CH₂)₂ Sn(L²)Cl₂, (C₆H₅CH₂)₂Sn(L²)Cl₂, (C₆H₅CH₂)₂Sn(L³)Cl₂, (p-ClC₆H₄CH₂)₂Sn(L³)Cl₂, (C₆H₅CH₂)₂Sn(L⁴)Cl₂, (C₆H₅CH₂)₃ Sn(L⁵)Cl, where L¹ = benzaldehyde phenylethylamine N-thiohydrazone, L²  = salicylaldehyde phenylethylamine N-thiohydrazone, L³ = p-methylacetophenone phenylethylamine N-thiohydrazone, L⁴ = cinnamaldehyde phenylethylamine N-thiohydrazone and L⁵ = benzaldehyde 2-phenylethyl N-(2-phenylethyl-N-thio)-1,2-ethanediamine. The complexes were pure and characterized by elemental analysis and molecular weight determination studies. Infrared and multinuclear (¹H, ¹³C, ¹¹⁹Sn NMR) spectra of the compounds are compatible with the presence of a neutral ligand attached to the metal through the S-C-N-N chelating system and formation of hexacoordinated tin complexes. Biological screenings for anti-tuberculosis, anti-fertility, anti-fungal (ED₅₀) and anti-bacterial activity were performed. Using thermogravimetric (TGA) and differential thermal analysis (DTA) various thermodynamic and kinetic parameters were calculated including reaction order (n), apparent activation energy (E_a), apparent activation entropy (S^#) and heat of reaction (ΔH) and correlated with the structural aspects for solid-state decomposition of complexes.

A Nano flower comprising a 3D Cd(II) coordination polymer, [Cd₂(pcih)(N₃)₃(CH₃OH)]_n (1), (pcih = 2-pyridinecarbaldehyde isonicotinoylhydrazonate), has been synthesized by a sonochemical process and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy and elemental analyses. Single crystalline material was obtained using a heat gradient applied to a solution of the reagents. Structural determination of compound 1 reveals two Cd(II) atoms with different coordination numbers. The structure may be considered a coordination polymer containing the Cd-(μ₂-1,1), Cd-(μ₃-1,1,1) and Cd-(μ₃-1,1,3) motifs, formed of three-dimensional chains. The strong π  -  π stacking interactions cause individual molecules to self-assemble to form a compressed supramolecular 3D network. Phase pure CdO nanoparticles were obtained by thermolysis of 1 in oleic acid at 180°C under an air atmosphere. The CdO nanoparticles were characterized by XRD and SEM.