Determination of in situ speciation of manganese in treated acid mine drainage water by using multiple diffusive gradients in thin films devices

Acid mine drainage (AMD) is a serious environmental problem that creates acidic solution with high Mn concentrations. The speciation of residual Mn from AMD after an active treatment involving the addition of a neutralizing agent can reliably evaluate the treatment efficiency and provide knowledge of the Mn species being inputted into the environment. The aim of this study was to evaluate the in situ lability and speciation of Mn using the diffusive gradients in thin films (DGT) technique with treated drainage water from a uranium mine (TAMD). DGT devices with different binding phases (Chelex-100 and P81 and DE81membranes) were used to perform the in situ speciation of Mn.     

Analysis of Calix[4]arenes Using Nonaqueous Capillary Electrophoresis

In nonaqueous capillary electrophoresis (NACE), an organic solvent is used in place of an aqueous medium as the background solution to improve the solubility and selectivity for hydrophobic analytes. In this study, we employed NACE with UV detection for the analysis of eight calix[4]arenes. We examined the influence of several parameters—the buffer composition, the nonaqueous solvent‘s composition and proportion, and the concentration of the electrolyte of the nonaqueous buffer—on the efficiency of the electrophoretic separation. The separation was achieved through the analyte's different effective mobility via different degrees of deprotonation on the phenolic OH groups of the calix[4]arene. This deprotonation can further affect the analyte's ability to form a complex with the metal ion. The optimized background electrolyte (BGE), comprising a mixture of N‐methylformamide/acetonitrile (30:70, v/v) and 100 mM AcOH/20 mM NH₄OAc, provided rapid (<11 min) separation of the calix[4]arenes with good resolution. The relative standard deviations of the migration times for the eight analytes were all less than 1%. Within the calibration concentration range, the coefficients of determination (R²) were all greater than 0.9914. Thus, the present study demonstrated NACE can provide adequate separation for the analysis of calix[4]arenes.     

A Convenient One-Pot Synthesis of N-Alkylanilines from Benzanilides

The direct synthesis of secondary amines from the corresponding primary amines by alkylation has been widely used. The major drawback, however, consists of polyalkylation. Several procedures exist for the solution of the problem. Some of the early methods involve reduction³, or alkylative hydrolysis⁴ of Schiff base. Other methods include acid hydrolysis of alkylated formanilides prepared from primary aromatic amine and trialkyl orthoformate⁵, or acid hydrolysis of N-alkylated phosphinamides⁶, or zinc cleavage of N-alkylated phenacylsulfonamides⁷, or reductive deprotection of N-alkylated trifluoromethanesulfonamides⁷. This latter method is analogous to the Gabriel synthesis of     

Are β‐H‐Eliminations or Alkene Insertions Feasible Elementary Steps in Catalytic Cycles Involving Gold(I) Alkyl Species or Gold(I) Hydrides?

The β‐H‐elimination in the (IPr)AuEt complex and its microscopic reverse, the insertion of ethene into (IPr)AuH, were investigated in a combined experimental and computational study. Our DFT‐D3 calculations predict free‐energy barriers of 49.7 and 36.4 kcal mol^?1 for the elimination and insertion process, respectively, which permit an estimation of the rate constants for these reactions according to classical transition‐state theory. The elimination/insertion pathway is found to involve a high‐energy ethene hydride species and is not significantly affected by continuum solvent effects. The high barriers found in the theoretical study were then confirmed experimentally by measuring decomposition temperatures for several different (IPr)Au^I‐alkyl complexes which, with a slow decomposition at 180 °C, are significantly higher than those of other transition‐metal alkyl complexes. In addition, at the same temperature, the decomposition of (IPr)AuPh and (IPr)AuMe, both of which cannot undergo β‐H‐elimination, indicates that the pathway for the observed decomposition at 180 °C is not a β‐H‐elimination. According to the calculations, the latter should not occur at temperatures below 200 °C. The microscopic reverse of the β‐H‐elimination, the insertion of ethene into the (IPr)AuH could neither be observed at pressures up to 8 bar at RT nor at 1 bar at 80 °C. The same is true for the strain‐activated norbornene.     

A Stable and Conductive Metallophthalocyanine Framework for Electrocatalytic Carbon Dioxide Reduction in Water

Transformation of carbon dioxide to high value‐added chemicals becomes a significant challenge for clean energy studies. Here a stable and conductive covalent organic framework was developed for electrocatalytic carbon dioxide reduction to carbon monoxide in aqueous solution. The cobalt(II) phthalocyanine catalysts are topologically connected via robust phenazine linkage into a two‐dimensional tetragonal framework that is stable under boiling water, acid, or base conditions. The 2D lattice enables full π conjugation along x and y directions as well as π conduction along the z axis across the π columns. With these structural features, the electrocatalytic framework exhibits a faradaic efficiency of 96 %, an exceptional turnover number up to 320 000, and a long‐term turnover frequency of 11 412 hour^?1, which is a 32‐fold improvement over molecular catalyst. The combination of catalytic activity, selectivity, efficiency, and durability is desirable for clean energy production.     

Synthesis,photoluminescence, and electrochromic properties of wholly aromatic polyamides bearing naphthylamine chromophores

A series of novel polyamides with pendent naphthylamine units having inherent viscosities of 0.15–1.02 dL/g were prepared via direct phosphorylation polycondensation from various diamines and a naphthylamine‐based aromatic dicarboxylic acid, 1‐[N,N‐di(4‐carboxyphenyl)amino]naphthalene. These amorphous polyamides were readily soluble in various organic solvents and could be cast into transparent and tough films. The aromatic polyamides had useful levels of thermal stability associated with high glass‐transition temperatures (268–355 °C), 10% weight loss temperatures in excess of 480 °C, and char yields at 800 °C in nitrogen higher than 60%. These polymers showed maximum ultraviolet–visible absorption at 350–358 nm and exhibited fluorescence emission maxima around 435–458 nm in N‐methyl‐2‐pyrrolidinone solutions with fluorescence quantum yields ranging from 0.4 to 15.0%. The hole‐transporting and electrochromic properties were examined with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium tin oxide coated glass substrate exhibited one oxidative redox couple around 1.08–1.16 V (oxidation onset potential) versus Ag/AgCl in an acetonitrile solution and revealed good stability of the electrochromic characteristics, with a color change from colorless to green at applied potentials ranging from 0 to 1.6 V. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6094–6102, 2006     

Photolytic transformation of aryl benzobisoxazole and aryl benzobisthiazole compounds into carbon dioxide

Solid‐state aryl benzobisoxazole and aryl benzobisthiazole compounds photolyzed in the presence of O₂ undergo cleavage to produce benzobisoxazoles (or benzobisthiazoles), benzonitriles, and benzamides. A very high percentage of the carbon atoms in one of the two segments from chain cleavage are converted to CO₂. This very unusual observation has been carefully confirmed by gas chromatography/mass spectroscopy analysis of the gaseous components in the photolysis vessel before and after photolysis, labeling experiments, and the correlation of the mass reduction in photolyzed polymers and the amount of CO₂ that evolves. The rate of CO₂ generation is used to compare the relative photostability of aryl benzobisoxazole and aryl benzobisthiazole model compounds, films, and fibers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1868–1877, 2007     

Functional Dihydro‐1H‐Imidazole Derivatives for MALDI Signal Enhancement of a Lysine‐Specific Chemical Modification

The enhancement of signal sensitivity and quantification of low‐abundance proteins is of great importance in proteomic analysis. The preparation of 2‐methoxy‐4,5‐dihydro‐1H‐imidazole (MeO‐DHIM) derivatives was accomplished by one‐step synthesis of O‐methyl‐isourea. The signal enhancement induced by these attached moieties increases in an order of compound 1 ≈? 4 < 2 < 5 ≈? 6 < 3 in MALDI mass spectrometry. Peptide‐compound 3 adduct was approximately 20 times signal enhancement of the unmodified peptide and of 9 times of the peptide‐compound 1 adduct. This result demonstrates that the rational designed organic molecules are capable of providing a sensitive tool in the detection of low‐abundance proteins in proteomics.     

Synthesis and interfacial behaviors of amphiphilic poly(oxypropylene) amidoacids

A series of hydrophobic poly(oxypropylene) (POP)‐backboned and hydrophilic poly(oxyethylene)‐backboned amidoacids and imidoacids were prepared through the reaction of poly(oxyalkylene) diamines and trimellitic anhydride (TMA) under mild conditions. The synthesized copolymers were characterized with nuclear magnetic resonance and Fourier transform infrared. Their ability to lower the water surface tension and toluene/water interfacial tension was measured and correlated with the hydrophobic/hydrophilic balance with multiple sodium carboxylate functionalities. The specific POP2000/TMA copolymers, consisting of a 2000 g/mol POP segment and multiple amidoacid functionalities, enabled the demonstration of a strong surfactant tendency and a critical micelle concentration at 0.1 wt %. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 646–652, 2006