Esterification of phthalic anhydride with 1-butanol and 2-ethylhexanol catalyzed by heteropolyacids

Esterification of phthalic anhydride with 2-ethylhexanol and 1-butanol and ester decomposition of dioctyl phthalate (DOP) in presence of Keggin; H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₄SiMo₁₂O₄₀, Wells–Dawson; H₆P₂W₁₈O₆₂, H₆P₂W₁₇MoO₆₂ and Preyssler; H₁₄[NaP₅W₂₉MoO₁₁₀], H₁₄[NaP₅W₃₀O₁₁₀], type heteropolyacids have been investigated. The heteropolyacids with Preyssler and Wells–Dawson structures and their molybdenum substituted derivatives show higher activity in esterification and ester decomposition reactions than Keggin type heteropolyacids. A complete conversion of phthalic anhydride to dioctyl phthalate and dibutyl phthalate are achieved in 2 h in presence of molybdenum substituted Preyssler heteropolyacid. In the decomposition of dioctyl phthalate in the presence of Preyssler heteropolyacid, 2-ethylhexene is formed in quantitative yield.     

A Comparative Study of the Electronic and Magnetic Properties of Gd5Ge4 and Gd5Si4 Compounds

We present a comparative study of electronic structure and magnetic properties of Gd₅Si₄ and Gd₅Ge₄ compounds using first principles full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) using the WIEN2k code. The local-spin density approximation with correlation energy (LSDA+U) method has been used as the exchange-correlation potential. The optimized lattice constants are in good agreement with the experimental data. The total and partial density of states (DOS) of Gd₅Si₄ and Gd₅Ge₄ show the difference in Si 3p-Gd 5d and Ge 4p-Gd 5d hybridization, which have an effective role in indirect exchange interaction. In addition, the magnetic moments of Gd, Si, and Ge atoms and the compounds are calculated to clarify the differences in the magnetic properties of these compounds.     

Construction of molecularly imprinted nanoparticles by employing ultrasound waves for selective determination of doxepin from human plasma samples: Modeling and optimization

In this work, molecularly imprinted nanoparticles (MINPs) were applied as selective adsorbent for ultrasound‐assisted micro‐solid‐phase extraction (UAMSPE) of doxepin (DP) from human plasma samples, which was then cleaned up, pre‐concentrated and subjected to HPLC. The MINPs were synthesized based on a non‐covalent approach by precipitation polymerization utilizing methacrylic acid and styrene as functional monomers, DP as template, ethylene glycol dimethacrylate as cross‐linker and 2,2‐azobisisobutyronitrile (AIBN) as initiator. The obtained MINPs were characterized by Fourier transform‐infrared and field emission scanning electron microscopy. Factors influencing the efficiency of UAMSPE such as sonication time, volume of eluent solvent and amount of sorbent were investigated using a central composite design and the optimal points were identified as 4 min of sonication time, 380 μL of eluent solvent and 30 mg of sorbent. Under optimized conditions, the proposed method has linear responses in the range of 0.2–2000 ng mL^–1, with a satisfactory limit of detection of 0.04 ng mL^–1 and limit of quantification of 0.11 ng mL^–1.     

DNA Binding and Antitumor Activity of a New Fluorescent Probe Eu(Ⅲ)-Complex Containing 4-Methyl-Coumarin Moiety

A new europium (Ⅲ) complex containing (4-Methyl-2-oxo-2H-chromen-7-yloxy)-acetic acid moiety (CMMC) was synthesized, characterized, and confirmed as antitumor agent and fluorescent probe. The spectroscopic measurements of Eu(Ⅲ) in the presence of CMMC were obtained in different solvents. The results show that the strongest Eu(Ⅲ) emission bands were monitored in iso-propyl alcohol while the weakest Eu(Ⅲ) emission band was observed in acetonitrile. The interaction of Eu(Ⅲ)-(CMMC)₂ complex with DNA was monitored using absorption and emission techniques. From fluorescence titration measurements, the binding constants of DNA with Eu(Ⅲ)-(CMMC)₂ complex were found to be 1.04×105 L·mol-1 in Tris-HCl and 1.17×107 L·mol-1 in DMSO-Tris-HCl buffer (9∶1 V/V). Hypochromism was observed from the absorption titration experiment which indicates the intercalation of Eu(Ⅲ)-complex between the base pair of DNA. This result further confirmed by fluorescent Ethidium bromide displacement assay. The fluorescence calibration curve was used for the determination of DNA with LOD of 1.2 ng in DMSO-Tris-HCl buffer (9∶1 V/V) and 5 ng in Tris-HCl buffer. The preliminary antitumor investigation shows promising cytotoxicity against MDA-MB-231, MCF-7 (mammary cancer), and PC-3 (prostate carcinoma) cell lines with IC₅₀ values of 40.63, 25.42 and 30.25 μmol·L-1, respectively.     

Synthesis of Stereoblock Elastomeric Poly(propylene)s Using a (2‐PhInd)2ZrCl2 Metallocene Catalyst in the Presence of Co‐Catalyst Mixtures: Study of Activity and Molecular Weight

The effect of adding various aluminum alkyls (R = Et, i‐Bu) on the polymerization of propylene is studied using a (2‐PhInd)₂ZrCl₂ pre‐catalyst. A mild deactivating effect is found upon addition of TIBA, whereas TEA shows a sharp deactivating effect. Increasing amounts of AlR₃ results in a significant activity increase for TIBA, but an activity plateau for TEA. AlR₃ imposes remarkably different effects on the molecular weight and stereochemical microstructure of polymers. As the TIBA concentration increases, $\overline {M} _{{\rm v}} $ increases at first, growing from 49 000 to 72 000, but subsequently drops to 40 000. For TEA, $\overline {M} _{{\rm v}} $ decreases sharply, plummeting from 49 000 to 17 000. Both TIBA and TEA increase the mmmm pentad content from 7.9 to 23.5% and 17.6%, respectively.

     

Effect of Si substitution on electronic structure and magnetic properties of Heusler compounds Co2TiAl1−xSix

The electronic structures of Co-based Heusler compounds CoTiAl_1−xSi_x (x=0, 0.25, 0.5, 0.75 and 1) are calculated by first-principles using the full potential linearized augmented plane wave (FP-LAPW) method within GGA and LSDA+U scheme. Particular emphasis was put on the role of the main group elements. In recent years, the GGA calculations of Co₂TiAl (x=0) and Co₂TiSi (x=1) indicated that they are half-metallic, but the electronic structure of this compound with x=0.25, 0.5 and 0.75 has not been reported yet, neither theoretically nor experimentally. The calculated results reveal that these are half-metallic and exhibit an energy gap in the minority spin state and also show 100% spin polarization. The substitution of Al by Si leads to an increase in the number of valence electrons, with increasing x. Our calculated results clearly show that with the Si doping, the lattice parameter linearly decreases; bulk modulus increases, and the total magnetic moment increases. The calculated energy gap in the minority spin state, using GGA scheme, was smaller than that obtained by using LSDA+U scheme. The outcomes of this research also show that the Co-3d DOS and therefore, the magnetic properties of compounds are dependent on electron concentration of the main group elements and it will affect the degree of p-d orbital occupation.     

Activity concentration of uranium in groundwater from uranium mineralized areas and its neighborhood

Uranium mineralization in parts of northeastern Nigeria necessitated its exploration during early eighties by the Nigeria Uranium Mining Company (NUMCO) which was later abandoned. During their course of decay, uranium isotopes pass through radioactive decay stage and eventually into stable isotope of lead. The course of concern for soluble uranium in groundwater especially from the mineralized areas include ionizing radiation, chemical toxicity and reproductive defects for which ingested uranium has been implicated to have caused. This study is aimed at assessing the levels of concentration of uranium in groundwater to ascertain its compliance with the World Health Organization’s (WHO) and the United State Environmental Protection Agency’s (EPA) guideline for uranium in drinking water. Thirty five groundwater samples were collected using EPA’s groundwater sampling protocol and analyzed at the Department of Geology, University of Cape Town using an Inductively Coupled Plasma Mass Spectrometric (ICP-MS) technique. Significant finding of this work was that there is radiological contamination of groundwater in the area. There is also an indication that the extent of radiological contamination is not much within the mineralized zones, therefore, there is likelihood that groundwater has acted as a medium of transporting and enhancing uranium in groundwater in an environment away from that of origin. About 5.7 % of the samples studied had uranium concentration above WHO and EPA’s maximum contaminant level of 30 μg/L which is a major concern for inhabitants of the area. It was also apparent that radiological contamination at the southwestern part of the study area extends into the adjacent sheet (sheet 152). Uranium concentration above set standards in those areas might have originated from rocks around established mineralized zones but was transported to those contaminated areas by groundwater that leaches across the host rock and subsequently mobilizing soluble uranium along with it.     

Trivalent phosphorus derivatives of group via : IV. Infrared and pmr studies of the protonation of M(CO)6−n(PA3)n Complexes (M = Mo,W; A = CH3, OCH3; n = 2, 3, 4)

The action of trifluoroacetic acid on the series M(CO)_6?n(PA₃)_n (M = Mo, W; A = CH₃, OCH₃; n = 2, 3, 4) has shown that protonation occurs if n ? 3. For n = 3 the basicity of the ligand PA₃ plays a more important role in the stability of [HM(CO)₃(PA₃)₃]⁺complexes than for n = 4. Infrared and proton NMR give evidence of the stereochemical non-rigidity of the [HM(CO)_6?n(PA₃)_n]⁺ heptacoordinated cation.