Poly (methyl methacrylate) grafted wheat straw for economical and eco-friendly treatment of oily wastewater

Cellulose - The sustainable development of oil–gas and petrochemical industries necessitates the development of cost-effective and eco-friendly technologies to treat mass-produced oily...     

Two polymorphs of a lead(II) complex with 8‐hydroxy‐2‐methylquinoline and thiocyanate

Two distinct polymorphs of bis(μ₂‐methylquinolin‐8‐olato)‐κ³N,O:O;κ³O:N,O‐bis[(isothiocyanato‐κN)lead(II)], [Pb₂(C₁₀H₈NO)₂(NCS)₂], (I), forming dinuclear complexes from a methanolic solution containing lead(II) nitrate, 2‐methylquinolin‐8‐ol (M‐Hq) and KSCN, crystallized concomitantly as colourless prisms [form (Ia)] and long thin colourless needles [form (Ib)]. In both cases, the complexes lie across a centre of inversion. The polymorphs differ substantially in their conformation and in their interactions, viz. Pb...S and π–π for form (Ia) and Pb...S, Pb...π and C—H...π for form (Ib).     

Synthesis and Crystal Structure of Bis(μ3-4-Oxapentan-2-onato)-Tetrakis(μ2-4-Oxapentan-2-onato)-Tetra-Magnesium Dichloride Dichloromethane

Abstract  

A new magnesium alkoxide which posses centrosymmetric tetranuclear structure derived from 1-methoxy-2-propanol, a functionalized alcohol containing asymmetric carbon. X-ray analysis of single crystal shows an open dicubane-like structure with triple-bridging alkoxo groups between alternating five- and six-coordinated magnesium atoms. There are six alkoxo bridging groups in which two of them bridge three metal centers and the other four bridge two. All of the etheric-oxygens are coordinated to magnesium and provide a rigid structure. Two chlorine atoms are bonded to five-coordinated magnesium. This compound crystallizes in the monoclinic system with a = 10.040(6) Ǻ, b = 14.004(9) Ǻ, c = 15.344(5) Ǻ, β = 95.55(9)˚, Z = 2 and V = 2147 Ǻ³ in the space group of P2₁/n.     

A single source precursor for low temperature processing of nanocrystalline MgAl2O4 spinel: synthesis and characterization of [MgAl2(μ3-O)(μ2-O(i)Pr)4(O(i)Pr)2]4

A novel polynuclear single-source precursor was prepared and characterized by single-crystal X-ray diffraction and multinuclear NMR spectroscopy. Nano-crystalline MgAl(2)O(4) spinel was synthesized via sol-gel processing of [MgAl(2)(μ(3)-O)(μ(2)-O(i)Pr)(4)(O(i)Pr)(2)](4). XRD, TGA-DSC and HRTEM confirmed the formation of a spinel phase at 475 °C, a temperature lower than any known processing temperature for MgAl(2)O(4).     

Synthesis,spectroscopy, electrochemistry and structural determination of asymmetric cobalt(III) Schiff base complexes

The [CoL(PR₃)(CH₃OH)]ClO₄ (where L = MeSalophen, 5-NO₂MeSalophen, 5-BrMeSalophen, 5-MeOMeSalophen, 4-MeOMeSalophen, 3-MeOMeSalophen and R=Ph or Bu) complexes were synthesized and also characterized by FTIR, UV–Vis, ¹H NMR and ¹³C NMR spectroscopies. The absorptions between 550 and 750 nm for the complexes are attributed to d–d transitions. Electrochemical properties of the complexes were examined by means of cyclic voltammetry. The anodic peak potentials were more positive in the following trend NO₂ > Br > H > MeO and are in accordance with electronic effects of the substituents. The crystal structure of [Co(5-NO₂MeSalophen)(PBu₃)(CH₃OH)]ClO₄ and [Co(5-BrMeSalophen)(PPh₃)(CH₃OH)]ClO₄ was determined by single-crystal X-ray diffraction. They showed six-coordinated pseudo-octahedral geometries in which equatorial planes are formed by the O(1), O(2), N(1) and N(2) atoms of the Schiff base and the axial positions were occupied by PR₃ and methanol.     

Synthesis,characterization and single crystal structure determination of aluminum alkoxydisilanolates: precursors for silica–alumina composite

Several novel aluminum alkoxydisilanolate complexes were prepared by reaction of triphenylsilanol with aluminum 2‐methoxyethoxide, aluminum 2‐ethoxyethoxide, aluminum sec‐butoxide and aluminum iso‐propoxide. All new complexes, [(Ph₃SiO)₂Al(OR)]₂ [where R = CH₂CH₂OCH₃ (1), CH₂CH₂OC₂H₅ (2), CH(CH₃)CH₂CH₃ (3) and CH(CH₃)₂ (4)] were characterized by elemental analysis, mass spectrometry and infrared spectroscopy (IR), as well as ¹H, ¹³C, ²⁹Si and ²⁷Al NMR spectroscopies. The solid‐state structures of the representative compound 2 and 4 were also verified by single‐crystal X‐ray analyses. Complexes 2 and 4 are dimers having distorted trigonal bipyramidal and tetrahedral coordination at the aluminum center, respectively. The ²⁷Al NMR spectrum of compound 2 showed that the solid‐state structure of the complex was not retained in solution, and tetracoordinated aluminum was found in solution in contrast to the pentacoordinated geometry in the solid state. The hydrothermal treatment of 1 and 4 at 200 °C and the subsequent calcination at 1000 °C resulted in the formation of alumina–silica composite (4SiO₂·Al₂O₃) with γ‐alumina in the silica matrix. Copyright © 2010 John Wiley & Sons, Ltd.     

Theoretical studies on the thermodynamics and kinetics of one-pot synthesis of aromatic PCP and PNP pincer ligands

In the present study, the kinetics and thermodynamics of the successful one-pot synthesis of arene-based PCP/PNP pincer ligands by less nucleophilic secondary halophosphines (mono/bis(phosphinomethyl)benzene/pyridine) via S_N2 reactions, which have been recently developed by Shih and Ozerov (Organometallics 34:4591, 35), have been studied. By utilizing different substituents on the target molecules, the impact of such modifications has been investigated both in gas phase and in solution. Performed calculations showed clear dependence of the activation energy and reaction rates on the presence of lithium in the structure. Additionally, the nature of the leaving group was observed to influence the favorability of the reaction. Similarly, the type of the halogen on both substrate and nucleophile had impact on the reaction rates, with the use of iodide leading to the observation of the fastest reaction rates. The solvent used was also noted to exert considerable influence on the thermodynamics and kinetics of the reactions. However, the R group in the nucleophile (XPR₂) showed no significant inductive effect on the activation energy, but a slight steric effect could be observed.     

Ultra‐deep desulfurization of a model fuel using novel VOHPO4 0.5H2O/boehmite catalysts

A high‐surface‐area boehmite was used as the support for a series of vanadium phosphate catalysts. The catalysts were prepared by heating of V₂O₅ in an isobutyl alcohol and benzyl alcohol mixture at 140°C for 5 h to reduce V⁵⁺ to more active V⁴⁺ in the presence of phosphoric acid. Then a series of catalysts with various VPO loadings on boehmite were synthesized. The catalysts were characterized using various techniques. The catalysts were utilized for extraction combined with catalytic oxidation of dibenzothiophene. The important factors influencing the desulfurization process, including reaction time, temperature, H₂O₂, catalyst loading, catalyst amount and solvents, were systematically investigated. Under the optimized reaction conditions, i.e. 30 mg of catalyst loading at 50°C and in 60 min, sulfur removal reached 94%. The catalyst was recycled and reused five times.     

The crystal structure of μ-Oxo-bis{diethoxy[salicylaldoximato(2-)]-tantalum(V)}

Stochiometric reaction of salicylaldoxime and tantalum or niobium ethoxide in toluene at room temperature resulted in formation of [M₂O(C₇H₅NO₂)₂(C₂H₅O)₄], M=Ta and Nb which were crystallized from CH₂Cl₂ at −5 °C and characterized by spectroscopic techniques. The molecular structures of [Ta₂O(C₇H₅NO₂)₂(C₂H₅O)₄] was determined by single-crystal X-ray diffraction and compared with molecular structure of [Nb₂O(C₇H₅NO₂)₂(C₂H₅O)₄]. The geometries at metal atoms are distorted octahedron which shared an apex through bridged oxygen. Each dianionic salicylaldoximate ligand chelates to the one metal ion through its phenolic oxygen and oximate nitrogen atoms, and to another metal ion through its oximate oxygen atom.