External Additives Research Articles

All-Solid-State, PVC Membrane, and Carbon Paste Ion-Selective Electrodes for Determination of Donepezil Hydrochloride in Pharmaceutical Formulation.

All-solid-state, polyvinyl chloride (PVC) membrane, and carbon paste potentiometric ion-selective electrodes (ISEs) were proposed for the determination of donepezil hydrochloride (DON) in the drug substance and a pharmaceutical formulation. The potentiometric response toward DON was based on the existence of donepezil-tetraphenyl borate (DON-TPB) in a PVC membrane or a carbon paste in the presence of dioctylphthalate. In contrast, the solid-state electrode was prepared by direct incorporation of DON-TPB into a commercial nail varnish without external additives. The electrodes exhibited Nernstian slopes of 55.0, 57.0, and 53.0 mV/decade over the concentration ranges of 1 × 10-5 to 1 × 10-3, 1 × 10-4 to 10-2, and 1 × 10-4 to 5 × 10-3 for the solid-state, PVC membrane, and carbon paste electrodes, respectively. The response of the electrodes is independent of pH in the range of 2-≤8. The electrodes showed good selectivity for DON with respect to a number of inorganic cations and amino acids. The electrodes were used for the determination of DON in pure solution and in pharmaceutical tablets with high accuracy (±2%) and precision (RSD ≤2%). The solid-state electrode is simple, economical, and rapid when compared to the PVC membrane and carbon paste electrodes.

Polymethylene-b-poly (acrylic acid) diblock copolymers: Aggregation and crystallization in the presence of CaCl2

Crystalline block copolymers tend to display a peculiar and intriguing behavior upon the external additives. In this work, we systematically investigated the self-assembly and crystallization behavior of polymethylene-b-poly (acrylic acid) crystalline diblock copolymer (PM-b-PAA, M93A94) in the presence of calcium chloride (CaCl2). When molar ratio between CaCl2 and constituent deprotonated carboxyl group (COO−) of M93A94 (n, n=nCaCl2/nCOO−) increased from 1:2 to 5:1, M93A94 micelle gradually formed hexagonal and reticular aggregation. Further investigation of PM-b-PAA crystalline feature indicated that the crystallization of PM block was initially restrained by coordination interaction between calcium ion (Ca2+) and carboxylate anion (COO−), and then the crystallization of PM block was promoted when more Ca2+ was added (nCaCl2/nCOO- reach to 5:1 and 13.5:1). Moreover, the conductivity measurement indicated that, when n (nCaCl2/nCOO−)=4, the coordination interaction between Ca2+ and COO− was saturated, namely CaCl2/PAA formed tetradentate complex, and this information concerning the coordination geometry was highly consistent with the simulative calculation.

All-Graphene Oxide Flexible Solid-State Supercapacitors with Enhanced Electrochemical Performance.

The rapid development of flexible and wearable electronics has led to an increase in the demand for flexible supercapacitors with enhanced electrochemical performance. Graphene oxide (GO) and reduced GO (rGO) exhibit several key properties required for supercapacitor components. Although solid-state rGO/GO/rGO supercapacitors with unique structures are promising, their moderate capacitance is inadequate for practical applications. Herein, we report a flexible solid-state rGO/GO/rGO supercapacitor comprising H2SO4-intercalated GO electrolyte/separator and pseudocapacitive rGO electrodes, which demonstrate excellent electrochemical performance. The resulting supercapacitor delivered an areal capacitance of 14.5 mF cm-2, which is among the highest values achieved for any rGO/GO/rGO supercapacitor. High ionic concentration and fast ion conduction in the H2SO4-intercalated GO electrolyte/separator and abundant CH defects, which serve as pseudocapacitive sites on the rGO electrode, were responsible for the high capacitance of this device. The rGO electrode, well separated by the H2SO4 molecular spacer, supplied highly efficient ion transport channels, leading to excellent rate capability. The highly packed rGO electrode and high specific capacitance resulted in a high volumetric energy density (1.24 mWh cm-3) observed in this supercapacitor. The structure, without a clear interface between GO and rGO, provides extremely low resistance and flexibility for devices. Our device operated in air (25 °C 40%) without the use of external electrolytes, conductive additives, and binders. Furthermore, we demonstrate a simple and versatile technique for supercapacitor fabrication by combining photoreduction and electrochemical treatment. These advantages are attractive for developing novel carbon-based energy devices with high device performance and low fabrication costs.

Acid-Functionalised Magnetic Ionic Liquid [AcMIm]FeCl4 as Catalyst for Oxidative Hydroxylation of Arylboronic Acids and Regioselective Friedel-Crafts Acylation.

An acid-functionalised, magnetic, room-temperature ionic liquid, 1-acyl-3-methylimidazolium tetrachloroferrate ([AcMIm]FeCl4 ), was synthesised and its optical, magnetic, and thermal properties were investigated. The magnetic moment (0.05402 emu in 2 T magnetic fields) showed strong paramagnetic behaviour, and thermogravimetric analysis indicated very good thermal stability with a decomposition temperature higher than 230 °C. Additionally, [AcMIm]FeCl4 efficiently catalysed the oxidative ipso-hydroxylation of arylboronic acids and regioselective Friedel-Crafts acylation without external organic solvent or additives, such as acids, base, and ligands. This functionalised ionic liquid, [AcMIm]FeCl4 , was recycled and reused at least six times without significant loss of its catalytic properties and stability.

Cobalt-Catalyzed Regioselective Ortho C(sp2)-H Bond Nitration of Aromatics through Proton-Coupled Electron Transfer Assistance.

A cobalt-catalyzed proton-coupled electron transfer (PCET) mediated regioselective ortho-specific nitration of aromatic C(sp2)-H bonds using chelation-assisted removable vicinal diamine directing groups was developed. The reaction proceeded under mild conditions in the presence of Co(OAc)2·4H2O as the catalyst with AgNO2 utilized as the nitro source as well as terminal oxidant in the presence of O2 as an external oxidant. No external base or additives were required for this process. Controlled experiments and mechanistic investigations with DFT calculations revealed that the reaction proceeds through a PCET promoted nitro functional group transfer pathway. Moreover, the produced compounds are valuable and pharmaceutically quite relevant.

Physico-chemical and dielectric relaxation studies of ionic surfactants in Time Domain Reflectometry (TDR)

The properties of aqueous surfactant solutions with external additives are extensively useful in surfactant-based systems. To study the dielectric relaxation studies of aqueous ionic surfactants (SDS, CTAB, DPC) and aqueous butanol, benzyl alcohol, aniline and tributylamine were carried out for different concentrations at 303k. Dielectric relaxation spectroscopy (DRS) is valuable for understanding the dynamic process mainly in micellar systems. Time domain dielectric data were obtained through HP54750A oscilloscope and TDR plug-in-module. The relaxation times were determined through the well-known Cole-Cole method. The superposition of two relaxation times gives the dielectric relaxation time obtained from the hydrated water molecule with rotations around the micelle, ions and another hydrophobic inner side of the micelle. Viscosity measurements were used to correlate the dielectric data. The Kirkwood correlation factor (g f ), effective Kirkwood correlation factor (g eff ), Bruggeman Factor (f B ), excess inverse relaxation time (1/τ) E , excess dielectric constant (e E ) and free energy of activation (ΔF t ) were also calculated. The effects of dielectric relaxation and viscous flow were interpreted and discussed.

Ullmann coupling of aryl chlorides in water catalyzed by palladium nanoparticles supported on amine-grafted porous aromatic polymer

A chemically stable porous carbonyl-incorporated aromatic polymer (CBAP-1(EDA)) was post-synthetically functionalized with ethylenediamine, and used as a solid support to immobilize the Pd nanoparticles (Pd@CBAP-1(EDA)) with particle size of 2–4nm using conventional chemical reduction. The synthesized Pd@CBAP-1(EDA) was characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM), thermogravimetric analysis (TGA), N2 adsorption-desorption isotherms, and inductively coupled plasma – optical emission spectrometry (ICP-OES). The obtained material was tested as a solid catalyst for the environmentally-benign Ullmann self-coupling of aryl chlorides in water medium, showing excellent catalytic performance for a series of aryl chlorides without the addition of any external additives. The catalyst was easily recovered by simple filtration and could be reused six times without loss of its initial activity. The high catalyst stability was confirmed by hot filtration and ICP analysis.

Rhenium‐Catalyzed Construction of Polycyclic Hydrocarbon Frameworks by a Unique Cyclization of 1,n‐Diynes Initiated by 1,1‐Difunctionalization with Carbon Nucleophiles

AbstractA regioselective cyclization of 1,n‐diynes under rhenium catalysis was developed on the basis of a rare type of 1,1‐difunctionalization of terminal alkynes with carbon nucleophiles, followed by sequential addition reactions of the resulting alkenylrhenium species. The reaction provides an efficient approach to the synthesis of complex cyclopentane‐fused bi‐ and tricycles and spirocycles, which are useful building blocks for the construction of essential frameworks of biologically active compounds as well as functional materials, from simple starting materials by the formation of up to six new carbon–carbon bonds in a single step. The reaction proceeds under neutral conditions and does not require external ligands or additives. The key to this reactivity is the unique activation mode of the rhenium carbonyl complex, which prefers to interact with heteroatoms in polar carbon–heteroatom bonds as well as nonpolar carbon–carbon unsaturated π bonds.

Rhenium‐Catalyzed Construction of Polycyclic Hydrocarbon Frameworks by a Unique Cyclization of 1,n‐Diynes Initiated by 1,1‐Difunctionalization with Carbon Nucleophiles

A regioselective cyclization of 1,n-diynes under rhenium catalysis was developed on the basis of a rare type of 1,1-difunctionalization of terminal alkynes with carbon nucleophiles, followed by sequential addition reactions of the resulting alkenylrhenium species. The reaction provides an efficient approach to the synthesis of complex cyclopentane-fused bi- and tricycles and spirocycles, which are useful building blocks for the construction of essential frameworks of biologically active compounds as well as functional materials, from simple starting materials by the formation of up to six new carbon-carbon bonds in a single step. The reaction proceeds under neutral conditions and does not require external ligands or additives. The key to this reactivity is the unique activation mode of the rhenium carbonyl complex, which prefers to interact with heteroatoms in polar carbon-heteroatom bonds as well as nonpolar carbon-carbon unsaturated π bonds.

Habit modification of tamoxifen crystals using antisolvent crystallizations

The crystal habit of tamoxifen was modified using antisolvent crystallization techniques. Tamoxifen was crystallized from organic solvents using two different antisolvents (water and carbon dioxide). The habit of the precipitated crystals was modified by changing the process conditions, such as the solution and antisolvent mixing rate, the organic solvent, the presence of ultrasonic waves, and the addition of external additives. Particle size, crystal habit, particle aspect ratio and powder XRD patterns of the precipitated tamoxifen crystals were measured. With water as the antisolvent, the particle size of tamoxifen was significantly reduced compared to that of the raw material. When the antisolvent was carbon dioxide, the particle size was an order of magnitude greater than that of the raw material. The average aspect ratio of the tamoxifen crystals ranged from 1.8 to 16.2. The presence of ultrasonic waves caused a significant reduction in the aspect ratio, as well as the particle size. Furthermore, the addition of external additives was found to influence the crystal habit of tamoxifen.

Assessment of Pulmonary Toxicity Induced by Inhaled Toner with External Additives.

We investigated the harmful effects of exposure to a toner with external additives by a long-term inhalation study using rats, examining pulmonary inflammation, oxidative stress, and histopathological changes in the lung. Wistar rats were exposed to a well-dispersed toner (mean of MMAD: 2.1 μm) at three mass concentrations of 1, 4, and 16 mg/m3 for 22.5 months, and the rats were sacrificed after 6 months, 12 months, and 22.5 months of exposure. The low and medium concentrations did not induce statistically significant pulmonary inflammation, but the high concentration did, and, in addition, a histopathological examination showed fibrosis in the lung. Although lung tumor was observed in one sample of high exposure for 22.5 months, the cause was not statistically significant. On the other hand, a persistent increase in 8-OHdG was observed in the high exposure group, indicating that DNA damage by oxidative stress with persistent inflammation leads to the formation of tumorigenesis. The results of our studies show that toners with external additives lead to pulmonary inflammation, oxidative stress, and fibrosis only at lung burdens beyond overload. These data suggest that toners with external additives may have low toxicity in the lung.

Unprecedented selective homogeneous cobalt-catalysed reductive alkoxylation of cyclic imides under mild conditions.

The first general and efficient non-noble metal-catalysed reductive C2-alkoxylation of cyclic imides (phthalimides and succinimides) is presented. Crucial for the success is the use of [Co(BF4)2·6H2O/triphos (L1)] combination and no external additives are required. Using the optimal cobalt-system, the hydrogenation of the aromatic ring of the parent phthalimide is avoided and only one of the carbonyl groups is selectively functionalized. The resulting products, N- and aryl-ring substituted 3-alkoxy-2,3-dihydro-1H-isoindolin-1-one and N-substituted 3-alkoxy-pyrrolidin-2-one derivatives, are prepared under mild conditions in good to excellent isolated yields. Intramolecular reductive couplings can also be performed affording tricyclic compounds in a one-step process. The present protocol opens the way to the development of new base-metal processes for the straightforward synthesis of functionalized N-heterocyclic compounds of pharmaceutical and biological interest.

Seed-induced Hydrothermal Synthesis of Tobermorite from Municipal Solid Waste Incinerator Fly Ash

Resource recovery of municipal solid waste (MSW) incinerator fly ash is widely concerned. Tobermorite, an important but rare naturally mineral, could not be directly hydrothermal synthesized from it owing to its high content of Ca but low concentration of Si and Al. The selected external silicon-aluminum additives including coal fly ash (CFA), bentonite, kaolin and diatomite were solely or combined added. With the addition of 30% mass composite additive in which the ratio of quality for CFA and diatomite is 1:1, tobermorite could be synthesized most effectively in 48h at 150°C, mainly attributing to the proper element proportion adjusted by additives. Tobermorite seed added could not only promote the large formation of tobermorite, but also inhibit the production of hibschite and kaotoite. Since Ca/(Si + Al) = 1.20 and Al/(Si + Al) = 0.20, addition of 30% mass of composite additive and 3% mass of tobermorite seed would be the recommended technological parameter.

Photosensitised regioselective [2+2]-cycloaddition of cinnamates and related alkenes.

An efficient method for the synthesis of substituted cyclobutanes from cinnamates, chalcones, and styrenes has been developed utilizing a visible-light triplet sensitisation mode. This reaction provides a diverse range of substituted cyclobutanes in high yields under mild conditions without the need of external additives. Good regioselectivity is obtained due to strong π-π-stacking of arene moieties, whereas diastereoselectivity relies on the electronic effects or ortho-substitution of the arene substrate. The utility of this transformation is demonstrated by the formal synthesis of the lignane natural product (±)-Tanegool.

A DFT study unveils the secret of how H2 is activated in the N-formylation of amines with CO2 and H2 catalyzed by Ru(ii) pincer complexes in the absence of exogenous additives.

We herein report a new H2 activation mechanism to elucidate the N-formylation of amines with CO2 and H2, catalyzed by Ru(ii) pincer complexes in the absence of exogenous additives. Furthermore, we show that the mechanism could be applied to other types of Ru(ii) pincer complexes and computed iron analogs.

Concentration dependent morphological transition of nanostructured self-assembly towards hydrogelation seeding from micellar aggregates through stereochemically optimized H-bonding network of amino acid derived cationic amphiphiles

The present work describes the concentration dependent gradual transition of hierarchical-morphology of anisotropic self-assembly towards hydrogel network seeding from micellarization that is primarily effected by supramolecular H-bonded interaction of optimal structural orientation of amide segment embedded in an amino-acid based cationic amphiphile: [Me3N+(CH2)3-(L)Xaa-C(O)C15H31 I− where (L)Xaa=L-Val (I) and L-Pro (II)] in absence of any external stimuli. Surfactants (I and II) show micellar property evidenced from tensiometric, conductometric and fluorescence anisotropy studies. Unlike II, I shows considerable change in their aggregate phase from giant micellar to worm like micellar behavior characterized from “Cole-Cole” plot for Maxwell-fluids which on higher concentration (∼3.5mM) leads to hydrogel as observed in rheological studies [G’ (storage modulus) >G” (loss modulus)] and presence of fibrous nano-structure in FESEM studies. The red shifted cotton band going from low to higher concentration for either of the amphiphiles suggests a conformational twist among the amide bonds rendering better packing arrangement. Both IR and CD studies signifies that the self-assembly of (I) is more like β-sheet type compared to (II) and can be rationalized based on their β-sheet stabilizing propensities whereas presence of Proline (a β-sheet breaker) with constrained cyclic pyrrolidine architecture, hinders the extended intermolecular H-bonding interaction.Such finer control over amphiphiles’ architecture leading to an extensive hierarchical transition in self-assembly from micelles to worm like micelles and finally to hydrogel solely through optimized H-bonding network in absence of any external additives is unequivocally evidenced through tailor made synthesis and physicochemical characterization.

Gold-Nanoparticle-Catalyzed Silaboration of Oxetanes and Unactivated Epoxides

Supported gold nanoparticles catalyze the unprecedented insertion of a silylborane into the C–O bond of oxetanes and unactivated epoxides, forming γ- or β-silyloxy boronates in good to excellent yields. In the silaboration process the boron moiety is acting as a nucleophile and the silyl as an electrophile. No external additives or ligands are required, while the catalytic system is recyclable and reusable.

Iridium(III)‐Catalyzed Regioselective Carbenoid Insertion C–H Alkylation by α‐Diazotized Meldrum's Acid

A practical and straightforward protocol for IrIII‐catalyzed regioselective carbenoid insertion C–H alkylation mediated by α‐diazotized Meldrum's acid was developed. The assistance of external additives and oxidants was not needed, and the developed IrIII catalysis proceeds in a highly efficient manner (e.g., mild reaction conditions, short reaction times and excellent regioselectivity) and demonstrates good compatibility with several privileged substrates, such as valuable N‐(2‐pyrimidyl)indoles, phenylpyridines, and the marketed drug edaravone and its analogues, and thus provides a good complement to previous methods for the rapid construction of the corresponding alkylated products.

Catalyst free, three-component approach for unsymmetrical triarylmethanes (TRAMs)

An efficient catalyst free, three-component, cascade approach has been designed and developed for the rapid assembly of unsymmetrical triarylmethane framework. The strategy employed aromatic aldehydes, Grignard reagents, and neutral aromatics as reaction partners, under simple thermal conditions. This process affords very broad scope for all three partners as it is performed in the absence of any external additives.

Palladium complexes catalyzed regioselective arylation of 2-oxindole via in situ C(sp2)−OH activation mediated by PyBroP

Pd(II) complexes appended with ONO pincer type ligand were synthesized, structurally characterized and successfully applied as catalysts for regieoselective C−2 arylation of 2-oxindole via in situ C (sp2)−OH activation in aqueous-organic media under an open atmosphere at room-temperature. This catalyst was reused up to four cycles. Favourably, the present protocol doesn't require the addition of any external oxidant, additives or phase transfer agents.