Target transform fitting in a voltammetric study of metal complexation

In this work target transform fitting (TTF) is proposed as a hard-model based data analysis method to analyze differential pulse polarograms recorded in a successive metal complexation system. In such cases, equations for both complexation equilibria and shape of the differential pulse polarogram for individual species are available. Utilizing TTF to fit these models in separate stages, stability constants and E_1/2 values of species were estimated. In the first stage, E_1/2 values of all species were acquired using the shape-equation of voltamograms and projection of a test vector into the row space of data matrix. In the second stage, using equations derived from relationships among species’ concentrations in complexation equilibria and a non-linear parameter fitting algorithm, the optimum values of overall formation constants were estimated. Finally, rank annihilation (RA) method was employed for calculation of diffusion coefficients. In spite of the fact that proposed method is a hard-model based approach, obtained results show that analysis can be performed correctly even in presence of unknown species. The reliability of the method was tested analyzing simulated data and also polarograms obtained from Cd(II) and 1, 10-phenanthroline complexation system. This experimental system yields three successive complexes which are relatively inert from electrochemical point of view. The results were in a good agreement with reported results in the literature.     

Recent progress in pillar[n]arene-based thin films on chemical sensor applications

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Pillar[n]arene is one of the most favorited supramolecular materials that possess a special chiral structure. The major property of...     

Magnetic metal-organic frameworks for the extraction of trace amounts of heavy metal ions prior to their determination by ICP-AES

Microchimica Acta - The authors describe the preparation of two kinds of metal-organic frameworks (MOFs), referred to as TMU-8 and TMU-9. The MOFs were applied to the preconcentration of the ions...     

Comparison of the separation of aziridine isomers applying heptakis(2,3-di-O-methyl-6-sulfato)beta-CD and heptakis(2,3-di-O-acetyl-6-sulfato)beta-CD in aqueous and nonaqueous systems

Aziridines are attracting interest as protease inhibitors, which might be used, e.g., for treatment of parasitic diseases. Within the framework of greater projects dealing with the search of new selective protease inhibitors, a huge number of aziridines with two stereogenic centers will be synthesized. Thus, a fast and reliable screening method for the evaluation of the isomeric composition is needed. Robust baseline separations were obtained using heptakis(2,3-di-O-acetyl-6-sulfato)beta-CD (HDAS) in acidic methanol and sulfated beta-CD in acidic phosphate buffer. With HDAS the resolutions were higher and migration times shorter. Thus, the method will be used as a screening method for further isomeric mixtures of aziridines.     

Experimental and thermodynamic modelling of systems containing water and ethylene glycol: Application to flow assurance and gas processing

Accurate knowledge of hydrate phase equilibrium in the presence of inhibitors is crucial to avoid gas hydrate formation problems and to design/optimize production, transportation and processing facilities. In this communication, we report new experimental dissociation data for various systems consisting of methane/water/ethylene glycol and natural gas/water/ethylene glycol. A statistical thermodynamic approach, with the Cubic-Plus-Association equation of state, is employed to model the phase equilibria. The hydrate-forming conditions are modelled by the solid solution theory of van der Waals and Platteeuw. The thermodynamic model was used to predict the hydrate dissociation conditions of methane and natural gases in the presence of distilled water or ethylene glycol aqueous solutions. Predictions of the developed model are validated against independent experimental data and the data generated in this work. A good agreement between predictions and experimental data is observed, supporting the reliability of the developed model.     

Characterization of RF Discharge in Liquid n-Hexane and its Application to Synthesize Carbon Nano-Particles

The RF plasma discharge in liquid n-hexane is used to synthesize carbon nanoparticles. The results show that amorphous carbon nanoparticles with size of 5?C25?nm are the main product in the plasma in liquid n-hexane. Carbon nano-tubes of average diameter of 19?nm and length of 500?nm are also observed. The energy efficiency for carbon nanoparticles production is 2.9?mg/kJ which is more than 10 times larger than that of typical arc discharge synthesis method. The high speed observation indicates that the RF plasma in liquid has an alternating behaviour and it does not continuously emit light. The OES results show that H and C₂ are the main observed species in the plasma. Based on the OES data, it is shown that plasma temperature is 4,030?K and the electron density is 2.54?×?10²²?m^?3. Our results suggest that this method can be considered as a new route for carbon nanostructures production.     

Comparison of ultrasound-assisted emulsification and dispersive liquid–liquid microextraction methods for the speciation of inorganic selenium in environmental water samples using low density extraction solvents

Herein, ultrasound-assisted emulsification microextraction (USAEME) and dispersive liquid–liquid microextraction (DLLME) methods based on applying low-density organic solvents have been critically compared for the speciation of inorganic selenium, Se(IV) (selenite) and Se(VI) (selenate) in environmental water samples by gas chromatography-flame ionization detection (GC-FID). At pH 2 and T = 75 °C for 7 min, only Se(IV) was able to form the piazselenol complex with 4-nitro-o-phenylenediamine. Piazselenol was extracted using an extraction solvent and was injected into a GC-FID instrument for the determination of Se(IV). Conveniently, Se(VI) remained in the aqueous phase. Total inorganic selenium was determined after the reduction of Se(VI) to Se(IV) and prior to the above procedures. The Se(VI) concentration was calculated as the difference between the measured total inorganic selenium and Se(IV) content. The effect of various experimental parameters on the efficiencies of the two methods and their optimum values were studied with the aid of response surface methodology and experimental design. Under the optimal conditions, the limit of detections (LODs) for Se(IV) obtained by USAEME-GC-FID and DLLME-GC-FID were 0.05 and 0.11 ng mL⁻¹, respectively. The relative standard deviations (RSDs, n = 6) for the measurement 10 ng mL⁻¹ of Se(IV) were 5.32% and 4.57% with the enrichment factors of 2491 and 1129 for USAEME-GC-FID and DLLME-GC-FID, respectively. Both methods were successfully applied to the analysis of inorganic selenium in different environmental water samples and certified reference material (NIST SRM 1643e).     

Pyridine analogues of the antimetastatic Ru(III) complex NAMI-A targeting non-covalent interactions with albumin

A series of pyridine-based derivatives of the antimetastatic Ru(III) complex imidazolium [trans-RuCl(4)(1H-imidazole)(DMSO-S)] (NAMI-A) have been synthesized along with their sodium-ion compensated analogues. These compounds have been characterized by X-ray crystallography, electron paramagnetic resonance (EPR), NMR, and electrochemistry, with the goal of probing their noncovalent interactions with human serum albumin (hsA). EPR studies show that the choice of imidazolium ligands and compensating ions does not strongly influence the rates of ligand exchange processes in aqueous buffer solutions. By contrast, the rate of formation and persistence of interactions of the complexes with hsA is found to be strongly dependent on the properties of the axial ligands. The stability of noncovalent binding is shown to correlate with the anticipated ability of the various pyridine ligands to interact with the hydrophobic binding domains of hsA. These interactions prevent the oligomerization of the complexes in solution and limit the rate of covalent binding to albumin amino acid side chains. Electrochemical studies demonstrate relatively high reduction potentials for these complexes, leading to the formation of Ru(II) species in aqueous solutions containing biological reducing agents, such as ascorbate. However, EPR measurements indicate that while noncovalent interactions with hsA do not prevent reduction, covalent binding produces persistent mononuclear Ru(III) species under these conditions.     

Ferrocene based chiral binuclear η6‐benzene‐Ru(II)‐phosphinite complexes: Synthesis,characterization and catalytic activity in asymmetric reduction of ketones

In the present study, a series of chiral C₂‐symmetric ferrocenyl based binuclear η⁶‐benzene‐Ru(II) complexes bearing diphenylphosphinite and diisopropylphosphinite moieties have been synthesised. The new binuclear η⁶‐benzene‐Ru(II)‐phosphinite complexes were characterised based on nuclear magnetic resonance (¹H, ¹³C, ³¹P–NMR), FT‐IR spectroscopy and elemental analysis. Then, these complexes have been screened as catalytic precursors in the transfer hydrogenation of acetophenone with 2‐propanol as both the hydrogen source and solvent in the presence of KOH. The corresponding optically active secondary alcohols were obtained in excellent conversion rates between 96 and 99% and moderate to good enantioselectivities (up to 78% ee). The complex 5 was the most efficient catalyst among the four new complexes investigated herein.     

Cellulose-Supported Ni(NO3)2 · 6H2O/2,4,6-Trichloro-1,3,5-triazine (TCT) as a Mild,Selective, and Biodegradable System for Nitration of Phenols

Nitration of certain phenols and naphthols in the presence of biodegradable cellulose-supported Ni(NO₃)₂ · 6H₂O/2,4,6-trichloro-1,3,5-triazine was carried out in acetonitrile at room temperature. Ortho nitrated phenols were obtained regioselectively within a short reaction time with good yields. The reaction condition was mild, and the employed cellulose could be recovered several times for further use.