Aqueous Solvent Media Research Articles

OXIDATION OF DL-METHIONINE, A SULFUR-CONTAINING AMINO ACID BY DIETHYL AMMONIUM CHLOROCHROMATE

Oxidation of DL-methionine (Met), sulphur-containing amino acid by Diethylammonium chlorochromate (DEACC) in dimethylsulphoxide (DMSO) is leading to produce its consecutive sulphoxide. The reaction is of first-order w. r. t. methionine and DEACC. The addition of an acid enhance the reaction rate, the effect of acidity is expressed by the relation kobs = a + b [H+ ]. The rate of the oxidation of methionine is recorded in 19 non aqueous solvent medium. The effect of solvent medium is was studied in nineteen different organic solvents. The solvent effect is evaluated by the models of Kamlet and Swain multiparametric equation. Importance of the cation solvating powers is predominantly seen in the effects of solvent medium. On the basis of results and discussion a suitable mechanism is proposed.

Synthesis and optical properties of AgInS2 nanoparticles

Ternary chalcogenide Ag-In quantum dots (QDs) are more environmentally friendly than known Cd-, Pb- and P-containing nanoparticles. Here we review the literature on colloidal synthesis methods, properties, and promising fields for the application of AgInS2 quantum dots. Similar to the QDs of lead and cadmium chalcogenides, the most accurate control over the structure and morphology of AgInS2 QDs is achieved by using the method of introducing precursors into high-boiling organic solvents. However, to realize the potential applications of ternary quantum dots, in particular as luminescent biomarkers, the quantum dots must be soluble in polar solvents, especially water. The transfer of quantum dots into aqueous solutions is usually accomplished by exchanging primary lyophilic ligands with smaller bifunctional molecules, such as thioglycolic (or mercapto­propionic) acids, which can passivate the surface of the quantum dots while making them soluble in the polar environment. Methods of colloidal synthesis of AgInS2 / ZnS quantum dots can be classified into the following types: Injection of ions into a high-boiling solvent Synthesis in a mixture of solvents Synthesis in the aquatic environment Methods for the synthesis of AgInS2 QDs in both aqueous solution and organic solvent medium are described. Examples of application of quantum dots for biomedical purposes and in photovoltaic and sensory devices are given. Quantum dots have high photostability and brightness, are characterized by a wide range of absorption and narrow spectral bands of radiation, ie meet most of the criteria for fluorescent materials and biosensors for imaging cancer cells in antitumor therapy, immunofluorescent labeling of proteins, detection of toxins s, visualize intracellular structures, etc. Quantum dots of tertiary chalcogenides, in particular CuInS2 and AgInS2, may be an alternative to quantum dots of binary lead and cadmium chalcogenides for use in light-emitting and light-absorbing systems, such as LEDs, sensors and solar absorbers.

Octahedron shaped lead sulfide nanocrystals as counter electrodes for quantum dot sensitized solar cells

PbS nanocrystals with octahedron shape are synthesized by a low temperature approach with presence of cation/anion surfactants in aqueous solution. CdS quantum dot sensitized solar cells (QDSSCs) based on these novel octahedron shaped PbS counter electrodes (CEs) are fabricated for the first time, achieving PCE of 1.54%. It is observed that the octahedron shaped PbS CE shows higher electrocatalytic activity compared with the Pt CE, indicating that the PbS nanocrystals with a uniformly distributed size is a superior candidate as CEs for QDSSCs application. This work may provide new route for preparing PbS from aqueous solvent medium through a simple synthesis route.

A pyrrole-containing cleft-type halogen bonding receptor for oxoanion recognition and sensing in aqueous solvent media

A halogen bonding pyrrole-bis(iodotriazolium) motif facilitates rarely observed augmented binding affinities and selective sensing of oxoanions (H2PO4− and SO42−).

Precision Epitaxy for Aqueous 1D and 2D Poly(ε-caprolactone) Assemblies.

The fabrication of monodisperse nanostructures of highly controlled size and morphology with spatially distinct functional regions is a current area of high interest in materials science. Achieving this control directly in a biologically relevant solvent, without affecting cell viability, opens the door to a wide range of biomedical applications, yet this remains a significant challenge. Herein, we report the preparation of biocompatible and biodegradable poly(ε-caprolactone) 1D (cylindrical) and 2D (platelet) micelles in water and alcoholic solvents via crystallization-driven self-assembly. Using epitaxial growth in an alcoholic solvent, we show exquisite control over the dimensions and dispersity of these nanostructures, allowing access to uniform morphologies and predictable dimensions based on the unimer-to-seed ratio. Furthermore, for the first time, we report epitaxial growth in aqueous solvent, achieving precise control over 1D nanostructures in water, an essential feature for any relevant biological application. Exploiting this further, a strong, biocompatible and fluorescent hydrogel was obtained as a result of living epitaxial growth in aqueous solvent and cell culture medium. MC3T3 and A549 cells were successfully encapsulated, demonstrating high viability (>95% after 4 days) in these novel hydrogel materials.

Identification and Determination of Phenolics in Lamiaceae Species by UPLC-DAD-ESI-MS/MS.

This study reports the phenolic profile screening of aromatic Lamiaceae species such as marjoram (Origanum majorana L.), lavender (Lavandula officinalis) and pennyroyal (Mentha pulegium L.) using a novel and validated ultra performance liquid chromatography method coupled with DAD diode array detector and tandem mass spectrometry (MS/MS) in negative mode of electrospray ionization. Identification and quantification of phenolics in these plant extracts has been realized within 12 min. This method showed good precision (percentage relative standard deviation; RSD% 0.54-2.72 for intra-day, 1.71-4.64 for inter-day), reproducibility (percentage recovery, REC% 92.0-109.0) and linearity (r = 0.9988-0.9999). Limits of detection ranged from 0.02 to 18.2 ng/mL. The extraction of plants was performed using microwave-assisted extraction technique and 60% (v/v) aqueous methanol solvent medium was selected as suitable solvent because of maximum extraction efficiency. Total antioxidant capacity, total phenolic content and free radical scavenging activity of these plant extracts were tested and the results correlated well among each other. According to the Folin assay, phenolic contents of Origanum majorana L., Mentha pulegium L. and Lavandula officinalis were calculated as 119 ± 3.4, 85.1 ± 2.8 and 57.8 ± 2.1 mg GAE/g dry matter, respectively.

Chelated charge assisted halogen bonding enhanced halide recognition by a pyridinium-iodotriazolium axle containing [2]rotaxane.

Four halogen and hydrogen bonding rotaxane host systems featuring pyridinium bis-amide-iodotriazole/prototriazole and pyridinium bis-amide-iodotriazolium/prototriazolium axle components have been synthesized by CuAAC-mediated mono-stoppering chloride anion templation and post-rotaxanation methylation reactions. In competitive 45 : 45 : 10 CDCl3-CD3OD-D2O aqueous solvent media, the dicationic halogen bonding rotaxane displayed a notable enhanced binding affinity and marked selectivity for Br- over other halides and nitrate and dihydrogen phosphate oxoanions in contrast to an all hydrogen bonding counterpart which is attributed to chelated charge assisted halogen bonding interactions.

Fabrication of cellulose self-assemblies and high-strength ordered cellulose films.

Based on the formation of cellulose hydrogels in NaOH/urea aqueous solvent media, cellulose self-assembly precursor is acquired. It is proved that the water uptake capability of the cellulose hydrogels depends highly on the cross-link degree (CLD) of cellulose. With varying CLD and concentration of cellulose, a variety of morphologies of cellulose self-assemblies, including sheets with perfect morphology, high-aspect-ratio fibers, and disorganized segments and network, are formed through evaporation. Furthermore, cellulose films are fabricated by diecasting and evaporating the cellulose hydrogels, resulting in a 3D-ordered structure of closely stacking of cellulose sheets. The mechanical test indicates both tensile strength and flexibility of the cellulose films are greatly improved, which is attributed to the formation of the orderly stacking of cellulose sheets. The study is expected to lay an important foundation on the preparation of ordered and high-strength cellulose materials.

Halotriazolium axle functionalised [2]rotaxanes for anion recognition: investigating the effects of halogen-bond donor and preorganisation.

The anion-templated synthesis of three novel halogen-bonding 5-halo-1,2,3-triazolium axle containing [2]rotaxanes is described, and the effects of altering the nature of the halogen-bond donor atom together with the degree of inter-component preorganisation on the anion-recognition properties of the interlocked host investigated. The ability of the bromotriazolium motif to direct the halide-anion-templated assembly of interpenetrated [2]pseudorotaxanes was studied initially; bromide was found to be the most effective template. As a consequence, bromide anion templation was used to synthesise the first bromotriazolium axle containing [2]rotaxane, the anion-binding properties of which, determined by (1) H NMR spectroscopic titration experiments, revealed enhanced bromide and iodide recognition relative to a hydrogen-bonding protic triazolium rotaxane analogue. Two halogen-bonding [2]rotaxanes with bromo- and iodotriazolium motifs integrated into shortened axles designed to increase inter-component preorganisation were also synthesised. Anion (1) H NMR spectroscopic titration experiments demonstrated that these rotaxanes were able to bind halide anions even more strongly, with the iodotriazolium axle integrated rotaxane capable of recognising halides in aqueous solvent media. Importantly, these observations suggest that a halogen-bonding interlocked host binding domain, in combination with increased inter-component preorganisation, are requisite design features for a potent anion receptor.

Diblock‐Copolymer‐Mediated Self‐Assembly of Protein‐Stabilized Iron Oxide Nanoparticle Clusters for Magnetic Resonance Imaging

Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (D<10 nm) SPIONs into large assemblies can considerably enhance their relaxivity. However, this assembly process is difficult to control and can easily result in unwanted aggregation and precipitation, which might further lead to lower contrast agent performance. Herein, we present highly stable protein-polymer double-stabilized SPIONs for improving contrast in MRI. We used a cationic-neutral double hydrophilic poly(N-methyl-2-vinyl pyridinium iodide-block-poly(ethylene oxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement.

Anion templated assembly of [2]catenanes capable of chloride anion recognition in aqueous solvent media

An anion templated double cyclization strategy to synthesize [2]catenanes in which two identical acyclic pyridinium receptor motifs interweave around a chloride anion template is described. Ring closing metathesis (RCM) of the preorganized orthogonal precursor chloride complex facilitates the isolation of [2]catenanes in very high yields. X-ray crystal structures provide an insight of the supramolecular forces responsible for chloride anion templated efficacy and recognition. Removal of the chloride anion template generates topologically unique interlocked binding cavities for anions. 1H NMR anion binding investigations demonstrate the catenanes to be highly selective hosts for chloride in preference to more basic monocharged oxoanions. In aqueous solvent media containing 30% water, such catenanes exclusively bind chloride, under which conditions no binding of acetate or dihydrogen phosphate is observed. Molecular dynamic simulations in the solution phase are used to account for the catenanes’ anion recognition properties.

ChemInform Abstract: Superheated Solvent Media for Organometallic (Poly)chalcogenide Cluster Synthesis

Abstract Solvothermal reactions in superheated aqueous and nonaqueous solvent media have led to many new metal-carbonyl chalcogenido clusters. This efficient synthetic technique, usually applied to synthesize solid state materials, is also surprisingly useful in preparing molecular clusters in crystalline form. Thus, many of the often laborious purification and separation procedures which are associated with conventional solution methods can be avoided. This method holds substantial promise for the exploratory synthesis of inorganic/organometallic compounds. In this short account we intend to focus on the contributions of the solventothermal technique to the organometallic polytelluride cluster chemistry.

Solvatochromism and solvation of transition metal complexes in ternary aqueous solvent media

The solvatochromic behaviour of a range of inorganic complexes, particularly iron(II)-cyanide-diimine species, is documented for a variety of ternary aqueous solvent media and the patterns observed discussed in terms of their solvation properties.

Increased paraoxon detection by acetylcholinesterase inactivation with ionic liquid additives

This is the first study using ionic liquids (ILs) as additive in the aqueous solvent medium for detection of paraoxon by acetylcholinesterase inhibition method. A systematic comparison of various ILs with organic solvents has been made. The aqueous buffer solution containing ionic liquid ethylpyridinium hexafluorophosphate [EtPy] +[PF 6] − has been found to give the best results. The inhibition kinetic follows the first order model. Ionic liquids modified aqueous solutions show the potential to provide a promising and effective medium in detection of paraoxon with acetylcholinesterase.

The use of free energy relationships to rationalise structural and solvent effects on the photoreduction of cobalt(III) complexes in aqueous organic solvent medium

Quantum yields for the photoreduction of a series of CoIII complex ions, [CoClen2 (RC6H4NH2)]2+ where R=p-OMe, p-OEt, p-Me, m-Me, H and p-F using a low pressure Hg vapour lamp (254 nm) in aqueous ethanol mixtures (15–40% v/v organic cosolvent), increase with increase in mole fraction of the cosolvent in the binary solvent mixture under investigation. The Hammett correlation is linear, affording negative reaction constants, which indicate that the excited state is electron deficient. Correlation of the quantum yield data with Kamlet–Taft's solvatochromic parameters indicates that the specific solvent–solute interactions play a dominant role in governing the reactivity.

Solubility of diphenyl sulfone in organic nonelectrolyte solvents. Comparison of observed versus predicted values based upon the general solvation model

Experimental solubilities are reported for diphenyl sulfone dissolved in 8 alkane, 10 alcohol, and in aqueous solvent media at 25°C. Results of these measurements are used to test the predictive ability of the general solvation model log CA,orgsat/CA,aqsat = c + rR2 + sπ2H + aΣα2H + bΣβ2H + vVxwhere CA,orgsat and CA,aqsat refer to the solute solubility in the organic solvent and in water, respectively, R2 is the solute's excess molar refraction, Vx is the McGowan characteristic volume of the solute, π2H denotes the solute's dipolarity/ polarizability, and Σα2H and Σβ2H are the overall hydrogen-bond acidity and basicity descriptors for the solute. The remaining symbols in the above expression are known solvent coefficients, which have been determined previously through regressional analysis of published organic solvent - water partition coefficient and vapor-liquid equilibrium data. Computations show that the general solvation model predicts the solubility behavior of diphenyl sulfone in the 11 organic solvents for which predictions could be made to within an overall average absolute deviation of about ±20%. Key words: diphenyl sulfone solubilities, organic solvents, solubility predictions, general solvation model.

Solubility of diphenyl sulfone in organic nonelectrolyte solvents. Comparison of observed versus predicted values based upon the general solvation model

Experimental solubilities are reported for diphenyl sulfone dissolved in 8 alkane, 10 alcohol, and in aqueous solvent media at 25°C. Results of these measurements are used to test the predictive ability of the general solvation model log CA,orgsat/CA,aqsat = c + rR2 + sπ2H + aΣα2H + bΣβ2H + vVxwhere CA,orgsat and CA,aqsat refer to the solute solubility in the organic solvent and in water, respectively, R2 is the solute's excess molar refraction, Vx is the McGowan characteristic volume of the solute, π2H denotes the solute's dipolarity/ polarizability, and Σα2H and Σβ2H are the overall hydrogen-bond acidity and basicity descriptors for the solute. The remaining symbols in the above expression are known solvent coefficients, which have been determined previously through regressional analysis of published organic solvent - water partition coefficient and vapor-liquid equilibrium data. Computations show that the general solvation model predicts the solubility behavior of diphenyl sulfone in the 11 organic solvents for which predictions could be made to within an overall average absolute deviation of about ±20%. Key words: diphenyl sulfone solubilities, organic solvents, solubility predictions, general solvation model.

ChemInform Abstract: Diels‐Alder Reactions Using Supercritical Water as an Aqueous Solvent Medium.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Diels-Alder reactions using supercritical water as an aqueous solvent medium

A variety of Diels-Alder reactions have been performed in supercritical water as a reaction medium. The rapid reaction of Diels-Alder reactions of cyclopentadiene and various electron poor dienophiles such as diethyl fumarate and acrylonitrile is observed in supercritical water, and leads to high yields of clean products without added catalysts.

Kinetics of dissociation of tris‐2,2′‐bipyridyl‐iron(II) cation in aqueous acetic acid solutions

AbstractThe kinetics of dissociation of tris‐2,2′‐bipyridyl‐iron(II) complex ion have been examined in aqueous acetic acid solutions. The reaction is first order in the complex ion; the dependence of rate on H+ is somewhat like that observed in aqueous solutions approaching a limiting value at higher H+ concentrations. The influence of solvent composition on the reaction rate under acid‐dependent and acid‐independent conditions shows an initial retardation by acetic acid. The argument of ion‐pair formation based on decrease of dielectric constant proposed to explain the kinetics in other aqueous solvent media was found useless to explain the behavior in acetic acid solutions. Other solvent parameters also did not provide satisfactory correlation with the kinetic results, thus, indicating the operation of more complex microscopic solute‐solvent and solvent‐solvent interactions. While solvent effects play some part in the rate process, the rate of reaction would tend to zero in the absence of H2O and H+. This interesting observation proved useful in proposing a reaction mechanism that is consistent with the rate behavior over the entire range of solvent composition. The activity of water in the reaction medium is controlled by the content of acetic acid which can effect the structure of water through operation of hydrophobic forces and formation of hydrates. While acetic acid cannot possibly fulfill the role of water in occupying the vacated coordination position, the anomalous rise in rate even under some water deficient conditions seems to be related to the coordinating ability of HSO4− derived from H2SO4 present in the solution.