Aqueous Ethanol Medium Research Articles

PREPARATION AND PHOTOLUMINESCENT PROPERTIES OF COMPLEXES OF TERBIUM, EUROPIUM AND THEIR COPRECIPITATES WITH METHYL ETHER 2-HYDROXYBENZOIC ACID

The amorphous coordination compounds of terbium (III) and europium (III) with methyl ester of 2-hydroxybenzoic acid, as well as their mixtures (coprecipitate), in the composition of TbxEu(1-x)L2OH·H2O, are isolated in a solid state by the method of coprecipitation from a weakly basic aqueous-ethanolic medium. According to elemental analysis and pH potentiometric studies, neutralization of cations’ charges is carried out by two molecules of dissociating ligand and one hydroxyl group. The method of thermogravimetric analysis has established that the water molecule that is part of the complexes is coordinated. According to the IR spectroscopy, the coordination of the ligand is carried out with the help of the oxygen atoms of the dissociating hydroxyl and the carbonyl group of the ester fragment. The obtained compounds are not volatile and when the mass spectra are registered in the BBA mode, they are completely destroyed. The complex of terbium (x = 1) in solid state exhibits an effective sensitized luminescence of green color, which is due to the intramolecular transfer of excitation energy from the ligand to the Tb3+ ion. The europium containing complex (x =0), which is isomorphic to terbium one, when excited by UV light, practically does not radiate due to the discrepancy between the energies of the triplet level of the ligand and the emission level of the Eu3+ ion. Sensitized f-f luminescence of the Eu3+ of red color be realized in solid precipitates of the complex mixture (x <1) due to the intermolecular transfer of the excitation energy from the terbium complex (III) to the compound of europium (III) (columinescence). The intensity of the glow of europium (III) depends on the ratio of ion emitters and reaches the maximum value at the values of Tb: Eu = 7: 3. At the same time there is a corresponding decrease in the intensity of the glow of terbium (III).

Synthesis, structure, and formation mechanisms of D-mannose alkali-catalyzed thermodestruction products in aqueous-ethanolic media

Synthesis, structure, and formation mechanisms of D-mannose alkali-catalyzed thermodestruction products in aqueous-ethanolic media

Starch films loaded with donut-shaped starch-quercetin microparticles: Characterization and release kinetics

Starch films loaded with donut-shaped starch-quercetin microparticles were prepared from two different botanical origins. The quercetin release kinetics through the films were studied. The donut-shaped starch-quercetin microparticles were prepared by thermal aqueous-alcoholic treatment. The quercetin loading percentage and therefore the antioxidant activity were higher for the microparticles from legume than those of cereal origins. The starch-quercetin microparticles also showed higher thermal stability than the starch granules.The starch films were produced using the solution casting method. The films with more microparticles content showed higher thermal stability. In-vitro release studies of the quercetin through the films were performed in aqueous-ethanolic medium. The quercetin released reached the equilibrium in 1 to 4 days for the films of cereal starch and in more than a week for the films of legume origin. The release data were fitted to Peppas–Sahlin model that suggests the release kinetics were controlled mainly by fickian diffusion. The produced biofilms can be utilized mainly for active food packaging applications.

Heterogeneous Pd/POSS Nanocatalysts for C–C Cross‐Coupling Reactions

AbstractAn insoluble solid support of N−heterocyclic imidazolium‐functionalized cage‐like silsesquioxane (SQ); Bim‐SQ, was synthesized by nucleophilic substitution of octakis(3‐chloropropyl)octasilsesquioxane with an excess bis‐(imidazol‐1‐yl)methane and investigated as a new organic‐inorganic hybrid support. In the presence of Bim‐SQ, Pd(II) from [PdCl4]2− can be stabilized via both electrostatic interactions and imidazole‐N‐coordination, giving an amorphous material of Pd(II)@Bim‐SQ. Subsequent in situ reduction of Pd(II)@Bim‐SQ during Suzuki−Miyaura cross‐coupling reactions afforded monodispersed Pd nanoparticles (2.33 ± 1.50 nm) stablized on Bim‐SQ support, PdNp@Bim‐SQ with Pd loading up to 14% w/w. Catalytic studies revealed that the pre‐catalyst Pd(II)@Bim‐SQ was active heterogeneous catalyst for Suzuki−Miyaura cross‐coupling reactions, having the maximum TOFs of 5400 h−1 under mild conditions and in aqueous ethanol medium. Furthermore, PdNp@Bim‐SQ was also shown to be an efficient catalyst for Heck reactions. Simple catalyst recovery and reusability of PdNp@Bim‐SQ for at least 5 catalytic cycles without loss of activity were also demonstrated.

Design and synthesis of a new class of 2,4-thiazolidinedione based macrocycles suitable for Fe3+sensing

Three 2,4-thiazolidinedione based macrocycles, which are very good Fe3+sensors in aqueous-ethanol medium, have been synthesized. X-ray crystallography, DFT calculations and MEP analysis have been used for their structural confirmation and for understanding their behavior towards Fe3+.

Effect of electrolytes on the solubility and solution thermodynamics of 1-amino-4-hydroxy-9,10-anthraquinone, an analogue of anthracycline anticancer drugs, in aqueous ethanol media using theoretical and UV–Vis spectroscopic study

The solubility of 1-amino-4-hydroxy-9,10-anthraquinone (AHAQ) in binary solvents (ethanol water mixtures) was determined at 298.15K under atmospheric pressure using a thermostatted reactor and analytical ‘UV–Vis spectroscopic method’. The structure of the molecule was optimized using theoretical studies to compute molecular dimension and the dipole moment which are essential in determining different thermodynamic parameters of solvation. The effects of binary solvents compositions and presence of electrolytes such as NaCl and KCl on the solubility were analyzed. Using the measured solubilities, the thermodynamic properties of dissolution of AHAQ such as Gibbs free energies of solutions, Gibbs free energetics due to cavity forming and dipole-dipole interactions, transfer enthalpy of dissolution, and chemical transfer energetics were calculated.

Extraction of Natural Surfactant Saponin from Soapnut (Sapindus mukorossi) and its Utilization in the Remediation of Hexavalent Chromium from Contaminated Water

AbstractIn this study optimization of extraction conditions for saponin from soapnut (Sapindus mukorossi) has been investigated. This investigation showed that a better extraction of saponin can be achieved with increasing the dielectric constant of solvent employed. The best yield was attained in a 50% v/v aqueous ethanol medium. Another objective of the present study is to assess the thermodynamics of the uptake-reduction of hexavalent chromium in contaminated water samples using saponin. Pyrene has been employed to determine the critical micellar concentration (CMC) (in the UV-vis method of determination) of saponin as a spectroscopic probe. Thus, the effectiveness of the bio-surfactant as a self-motivated adsorbent for hexavalent chromium is investigated. Several physico-chemical parameters like contact time, sorbate concentration, pH and temperature have been determined. The findings of the investigation invoked a very efficient uptake of 213.48 mg g−1 of hexavalent chromium from the contaminated water sample at a lower value of pH 2 and temperature 35°C. It is observed that the method followed a pseudo-first order kinetics, where the evaluated ΔG0 has supported the sorption as a feasible and spontaneous process. The HR-MS, FTIR, steady state Fluorescence spectroscopy, HR-TEM and UV-Vis spectroscopy have been employed for the current scientific studies.

A new biphenylcarbonitrile based fluorescent sensor for Zn2+ ions and application in living cells

A new and efficient fluorescent sensor 4′-hydroxy-3′-[(4-antipyrineimino)methyl]-4-biphenylcarboni- trile(L) was prepared for the selective detection of Zn2+ in aqueous ethanol medium. When excited at 419 nm, the fluorescent intensity of sensor L at 507 nm was remarkably increased more than 54-fold after adding Zn2+ ions. The strong green emission of the solution can be easily identified by naked eye under UV light. Thus, sensor L behaves as a naked eye fluorescent “turn on” detector for Zn2+ ions. The fluorescence enhancement might be attributed to the inhibition of excited state intramolecular proton transfer(ESIPT) and C=N isomerization as well as the chelation enhanced fluorescence(CHEF) effect. The complex solution of sensor L with Zn2+ ions exhibited reversibility with ethylene diamine tetraacetic acid(EDTA) and the probe could be recycled for further use. Notably, sensor L could clearly distinguish Zn2+ from Cd2+. The interaction of sensor L with zinc ions was investigated by means of FTIR, 1H NMR and HRMS spectroscopy. Furthermore, sensor L has been applied for cell imaging studies.

ИЗУЧЕНИЕ ДИАЛИЗУЕМЫХ МЕЛАНОИДИНОВЫХ ФРАКЦИЙ ВОДНО-ЭТАНОЛЬНЫХ СИСТЕМ D-ЛАКТОЗА – АРИЛАМИН

Dialyzable fractions of brown polymers synthesized in amino-carbonyl interaction of D-lactose with p-toluidine under condition of acid catalysis in aqueous-ethanolic media was studied by UV-Vis spectrophotometry. To study of the fraction’s compositions and their dialysis dynamics two parallel series spectra of dialysates were measured. It is obtained that non-nitrogenous derivatives in dialyzable fractions are presented as weakly colored products with furan structural fragments, the main nitrogenous component is p-toluidine eliminated by the Amadori rearrangement product’s degradation.

An Efficient Synthesis of Spiro[indoline-3,9'-xanthene]trione Derivatives Catalyzed by Magnesium Perchlorate.

A simple and efficient method for the synthesis of spiro[indoline-3,9′-xanthene]trione derivatives by means of condensation between isatins and 1,3-cyclohexanedione in the presence of a catalytic amount of magnesium perchlorate at 80 °C in 50% aqueous ethanol medium has been described. Notably, the present method offers desirable advantages of good yields, simplicity of workup procedure, easy purification, and reduced reaction times.

TiO2[sbnd]ZnO photocatalysts synthesized by sol–gel auto-ignition technique for hydrogen production

The present work investigates Zn doped TiO2 (1.0, 5.0, 10.0, 12.0 and 30.0 wt.% Zn) photo-catalysts; prepared by sol–gel auto-ignition method, which were systematically investigated to configure their structural, surface, optical and morphological properties via using X-ray diffractometer (XRD), Scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared spectrometer (FTIR), and UV–Vis spectrophotometer. The photocatalytic H2 evolution using the TiO2ZnO suspensions was evaluated in a 25 vol.% aqueous ethanol medium using UV illumination (Hg lamp λ = 254 nm, 2.2 mW/cm2). The Zn+2 concentrations utilized to prepare TiO2ZnO nanocomposites were found to have significant effects on specific surface areas, energy band gaps (Eg), efficient separation of charged pairs and thus affected the photocatalytic performances. The photocatalytic activity of the TiO2–10 wt.% ZnO composite has reached an optimal H2 production of 1048 μmol h−1 exceeding those of the pure TiO2 (151 μmol h−1) and TiO2 P25 (595 μmol h−1) photocatalysts.

Simple and efficient approach for synthesis of hydrazones from carbonyl compounds and hydrazides catalyzed by meglumine

ABSTRACTA simple, environmentally benign protocol for synthesis of hydrazones from carbonyl compounds and hydrazides has been developed in the presence of meglumine in aqueous-ethanol media at room temperature. The salient features of the present protocol are mild reaction conditions, short reaction time, high yields, operational simplicity, metal-free, applicability toward large-scale synthesis, and biodegradable and inexpensive catalyst.

A Novel Method for the Synthesis of Newfangled Asymmetric Schiff Bases from α‐amino Acids under Ultrasonic Conditions and in Aqueous Medium

Chiral Schiff bases were obtained at high yields via a novel technique. Aryl aldehydes and chiral α‐amino acids were treated (1) in the presence of H3PO4 in ethanol at 80°C for 24 h, and (2) in the presence of K2CO3 under ultrasonic conditions in an aqueous ethanol medium within 5 min with yields reaching up to 96%. The results showed that the presented methodology under ultrasonic conditions was effective, practical, and eco‐friendly compared to that using an acidic medium. The corresponding asymmetric Schiff bases were synthesized for the first time, and were characterized by 1H and 13C nuclear magnetic resonance and infrared spectroscopy and high‐resolution mass spectrometry.

Molecular mobility of nanocellulose hydrogels

The molecular mobility of nanocellulose hydrogels isolated from microcrystalline cellulose is evaluated using the spin probe method, from the correlation time τ (s) and rotational frequency ν = 1/τ(s–1) of stable nitroxyl radicals introduced into the medium under study. In an aqueous gel medium, the EPR spectrum of the probe features an anisotropic triplet of frozen particles over a temperature range of 77 to 265 K. In an aqueous–ethanolic gel solution, the temperature of onset of rotation of the radical is 85 K lower. The rotational correlation time is determined from the parameters of the EPR spectrum recorded in the temperature range of 180–290 K. The resulting Arrhenius temperature dependence logν = f(1/T) is used to evaluate the activation energy of rotation E of the radical and the preexponential factor ν0(s–1), the frequency of rotational vibrations of the particle around the equilibrium position. For the aqueous medium, E = 11.2 kcal/mol; in the presence of ethanol, E = 5.2 kcal/mol; the preexponential factors for the aqueous and aqueous–ethanolic media are ν0 = 7 × 1018 and 6 × 1014 s–1, respectively. The parameters E and ν0 measured in the pure solvents and in the samples containing nanocellulose differ little, which is indicative of a high hydrophobicity of the probe molecule (and hydrogel particles) and of their weak interaction with the environment. The high value (~1018 s–1) of the preexponential factor is explained in terms of the compensation effect of water.

A new entry to synthesis of neocryptolepine related skeletons. An unexpected behavior of 3-acety-2-ethoxyindole and isatins

An unexpected and intriguing reaction to the direct construction of indolo[2,3-b]quinoline ring system of neocryptolepine analogues was discovered through simple heating of 3-acetyl-2-ethoxyindole with isatins in 10% aqueous ethanol media with the presence of KOH as the base. The process is very clean and avoids the use of toxic organic solvent, thereby enhancing the greenness of the transformation. Moreover, the newly-synthesized compounds bearing a pendant carboxyl group at the C-11 position of indolo[2,3-b]quinoline skeleton could be potentially applied as useful synthetic building blocks for more complex indolo[2,3-b]quinoline alkaloid derivatives.

A highly selective and sensitive “Turn-On” fluorescence chemosensor for the Cu 2+ ion in aqueous ethanolic medium and its application in live cell imaging

Abstract A new rhodamine 6G derived chemosensor L has been synthesized that selectively detects the presence of Cu 2+ ion over a host of other biologically important and environmentally relevant metal ions in aqueous alcoholic medium under physiological pH (ethanol: water, 1:1, v/v, pH 7.2). The significant enhancement of fluorescence intensity of L is caused by Cu 2+ ion induced cleavage of spirolactum bond in the rhodamine moiety. This mechanism is well supported by the crystal structure of the L-Cu 2+ complex that depicts two ligand units are bonded to two Cu 2+ ions. Color of the solution changes from light orange to dark pink upon metal binding which allows naked eye detection ion as well. Confocal microscopic experiments validate that the dye is potentially useful for the selective detection of Cu 2+ ion in living cells. Therefore the dye is an excellent fluorogenic and chromogenic chemosensor for the Cu 2+ ion in aqueous ethanolic medium and the living cell as well.

Stability of curcumin in different solvent and solution media: UV–visible and steady-state fluorescence spectral study

In aqueous solution, curcumin is photodegradable (light sensitive), it is also self-degradable in the dark. In basic medium, the second process is enhanced. The dark process has been studied in water and also in a number of protic and aprotic solvents, and aqueous solutions of ionic liquids, pluronics, reverse micelles and salt. The kinetics of the process followed the first order rate law; a comparative as well as individual assessment of which has been made. The kinetics of curcumin self-degradation has been found to be fairly dependent on salt (NaCl) concentration. Curcumin molecules in solution may remain in the enol or keto–enol form. From the visible spectral analysis, an estimate of the proportions of these forms in aqueous ethanol medium has been made. The temperature effect on the visible and fluorescence spectra of curcumin has been also studied. The steady state fluorescence anisotropy of the photoactive curcumin has been evaluated in different solvent and solution media. The reversibility of the steady state fluorescence anisotropy of curcumin on heating and cooling conditions has been examined. The results herein presented are new and ought to be useful as the study of physicochemistry of curcumin has been gaining importance in the light of its biological importance.

Oxidoperoxidomolybdenum(VI) complexes involving 4-formyl-3-methyl-1-phenyl-2-pyrazoline-5-one and some β-diketoenolates

Five new oxidoperoxidomolybdenum(VI) complexes of the general composition [MoO(O2)(fmphp)(L)], where fmphpH = 4-formyl-3-methyl-1-phenyl-2-pyrazoline-5-one and LH = acetylacetone, methyl acetoacetate, benzoylacetone, acetoacetanilide or o-acetotoluidide, have been synthesized by the interaction of [MoO(O2)]2+ (obtained in situ during the interaction of MoO3 and 30 % H2O2 on continuous stirring at 50 °C for 24 h) and the said ligands in aqueous-ethanol medium. The complexes were characterized by physicochemical analyses involving magnetic measurements, infrared, electronic, mass spectral and thermal studies. Besides applying experimental spectroscopic techniques, theoretical data calculated using density functional theory (DFT) by B3LYP/LANL2DZ have also been used for structural determination. In addition to an optimized geometry with no imaginary frequency, the computed spectral data have been found in an excellent agreement with the experimental results. Thermo-gravimetric (TG) curve was used to arrive at the insights of thermal stability of one of the synthesized complexes. From overall studies, suitable heptacoordinate pseudo-pentagonal bipyramidal geometry has been found for the title compounds.

A chemosensor for Al3+ ions in aqueous ethanol media: photophysical and live cell imaging studies

A new rhodamine based highly sensitive “Turn-ON” fluorescent chemosensor L for the selective detection of Al3+ ion over other biologically competing metal ions in aqueous ethanol media.

Synthesis and Characterization of Fe3O4@SiO2 NPs as an Effective Catalyst for the Synthesis of Tetrahydrobenzo[a]xanthen-11-ones.

In this research, the significant application of Fe(3)O(4)@SiO(2) core-shell nanoparticles as an efficient, green, robust, cost-effective and recoverable nanocatalyst for multi-component reaction of aldehydes, 2-naphthol and dimedone has been developed in aqueous ethanol media under reflux conditions. This procedure also avoids hazardous reagents/solvents, and thus can be an eco-friendly alternative to the existing methods. Simple procedure, environmentally benign, excellent yields, short reaction times, simple purification and facile catalyst separation are advantages of this protocol. Characterization and structural elucidation of the products have been done on the basis of chemical, analytical and spectral analysis and also the heterogeneous nanoparticles were fully characterized by FT-IR, XRD, EDX, VSM and SEM analysis.