Aqueous Organic Media Research Articles

Probing the bilayer-monolayer switching of capping agents on Au nanorods and its interaction with guest molecules $$^{\S }$$ §

The anisotropic features of Au nanorods make them an attractive nanoscale precursor for the design of higher order nanostructured materials. However, the mode of interaction of various molecular systems on Au nanorods is not well-understood. In the present study, we have employed isothermal titration calorimetry and surface-enhanced Raman scattering for understanding various types of interactions of functional molecules on the surface of gold nanorods. The binding of thiol-bearing analyte molecules is effective with the surface of gold nanorods in acetonitrile-rich solvents and found to be weak in an aqueous medium. The effective interaction of thiol-bearing analyte molecules on nanorods is facilitated by the breakdown of cetyltrimethylammonium bromide bilayer to a monolayer in organic-rich solvent systems, thereby resulting in appreciable signals in isothermal titration calorimetry and surface-enhanced Raman spectra. The electrostatic interaction of analyte molecule is mainly driven by the charge reversal on the surface of Au nanorods on switching the solvent from aqueous to organic medium. Thus, based on isothermal titration calorimetry and surface-enhanced Raman scattering investigations, it is established that the microheterogeneous environment around the Au nanorods plays a crucial role in driving the interaction of analyte molecules. SYNOPSIS Cetyltrimethylammonium bromide on Au nanorod exists as a bilayer in water and as a monolayer in aqueous-organic medium, which in turn influences the surface charge and plays a crucial role in driving the substrate-analyte interactions.

Chemical sensor using metal-organic complex: Preparation, characterization and application for highly selective detection of cyanide ions in mixed aqueous-organic media

In this study, a novel metal-organic hybrid material (MO1) was designed and synthesized for the detection of CN− ions. The spectral analyses by FT-IR, 1H NMR, 13C NMR, CHN and TGA satisfactorily confirmed the structure of MO1. The sensor MO1 was applied as colorimetric probe for sensing of cyanide ions in aqueous solutions of dimethyl sulfoxide. MO1 with electron withdrawing group at organic ligand showed high selectivity for detection of cyanide over other interfering anions. Interaction of MO1 with cyanide provides obvious colorimetric change from red to violet, enabling easy detect with the naked eye. In addition, the sensing details were evaluated using UV–vis spectroscopy. Furthermore, the detection limit of chemosensor toward CN‾ ions was found to be 5.52 μM. Moreover, probe MO1 can be used for selective sensing of cyanide based on the obvious color changes in real samples.

THE ELECTRON DONATING PROPERTIES OF NITROGENCONTAINING ORGANIC BASES IN WATER-ETHANOL AND WATER-ACETONE SOLUTIONS

In this paper, the dissociation constants (pKa) of some nitrogen-containing organic bases (aniline, pyridine and octylamine) in water-ethanol and water-acetone media at various concentrations of organic solvent in the system has been determined by the potentiometric titration method. It was established that the value of pKa of nitrogen-containing organic bases in aqueous-organic media naturally decreases with increasing content of organic solvent in the system. It was shown that their nature (aliphatic, aromatic, heterocyclic) and the physicochemical properties of the medium are significantly influenced by the nature and degree of change in the electron donor ability of the nitrogen-containing organic bases studied. It was noted that for aniline in water-ethanol solutions in the transition from water to an organic solvent, the value of pKa does not change much (ΔpKa = 0,9), while for pyridine and octylamine these changes are significant, and the values of ΔpKa are 2,9 and 1,7, respectively, which can be explained by the specific solvation of the aniline amino group with ethanol. In the case of water-acetone solutions, the behavior of the nitrogen-containing organic bases was studied generally similar, and the values of ΔpKa are within the range of 1,7-2,6. It was established that the dependence of the values of pKa of nitrogen-containing organic bases on the inverse of the dielectric constant of water-ethanol and water-acetone solutions tends to be linear, consistent with Izmailov’s theory. Thus, we can conclude that the change in the ratio of the mixed solvent components and, as a result, in general, dielectric permeability of the medium does not lead to a significant change in the solvation characteristics of the nitrogencontaining organic bases studied.

Synthesis and Aggregation of Cationic Zinc and Magnesium Phthalocyanines Containing 4-(3,5-Dimethyl-1H-pyrazol-1-yl)phenoxy Groups

Tetracationic metal phthalocyanines were synthesized by the quaternization of the Cs-regioisomers of tetrasubstituted zinc and magnesium phthalocyanines containing 3,5-dimethylpyrazole fragments. The individuality of the synthesized compounds was confirmed by HPLC‒mass spectrometry. The aggregation of the cationic metal phthalocyanines in water and aqueous-organic media, as well as in the presence of Triton X- 100 was studied. The dependence of the dimerization constant on the polarity of mixed solvents was determined.

Luminescence kinetics of CdSe-based quantum dots in toluene

Luminescence kinetics of quantum dots (CdSe-CdS core-shell nanoparticles) in toluene were studied. Quantum dots were obtained through colloidal synthesis method in aqueous-organic media with the average size estimated as 2 nm and 2.9 nm from the position of the exciton absorption peak. A biexponential luminescence decays with time constants of a few and tens of picoseconds were observed via up-conversion technique

Expanding Application of Immobilized Candida Antarctica Lipase B: A Green Enzyme Catalyst for Knoevenagel Condensation Reaction

We propose a green synthesis of benzopyran compound based on immobilized lipase. Firstly, by using a combined electrospun membrane and biocompatible chitosan, we show that the chitosan-functionalized electrospun PMA-co-PAA fibrous membrane can provide effective anchoring sites for immobilization of the Candida antarctica lipase B (CALB), and a maximum loading amount of CALB (152 mg/g) can be achieved. Then, the resulting membrane displays enhanced stability in catalyzing Knoevenagel condensation reaction of salicylaldehyde with active methylene compound in mixed aqueousorganic media. The catalytic activity and stability of the CALB on chitosan-modified fiber is better than its non-immobilized counterpart. Furthermore, this immobilize CALB catalyst still retained about 45 % of the initial activity after 5 cycles, which potentially had implications for the design of “green” enzyme catalyst for sustainable organic synthesis.

INTERPOLYELECTROLYTE COMPLEXATION OF SULFONATE-CONTAINING AROMATIC POLY- AND COPOLYAMIDES IN ORGANIC AND AQUEOUS-ORGANIC MEDIA

Complex formation of sulfonate-containing aromatic poly- and copolyamides with copolymers of acrylonitrile with N,N-dimethyl-N,N-diallylammonium chloride and N,N-diethylaminoethyl methacrylate was studied in organic and aqueous-organic media. The values of conversion degree for interpolymer reactions were determined. At optimal conditions in the presence of poly-4,4'-(2-sodium sulfonate)diphenylaminoisophthalamide and poly-4,4'-(2-sodium sulfonate)diphenylaminoterephthalamide the degree of conversion was equal to ~0.80 and 0.78, respectively. The reduction of number of sulfonate containing units in the polymer chain to 10% leads to its decrease to ~0.18. It was shown that the nature and composition of the solvent affects the kinetics of interpolymer reactions due to the different ratio of reaggregation during the interacting of function groups in water medium with considerable force of hydrophobic interactions and in organic solvent where these forces dramatically reduce. The phase state and the composition of formed interpolyelectrolyte complexes depends on charge density along macromolecule chain of copolyamide and on the composition of the solvent used. The reduction of the number of sulfonate containing units in the macromolecule leads to polycation component increase in the complex. The formation of stoichiometric interpoly-electrolyte complexes takes place in the solvent with the same composition as that when the most significant unfolding of the polyanion chain was observed. The phase separation during the complex formation by the interpolymer reaction with copolyamide containing 5% of units with sulfonate groups or copolymer of acrylonitrile with N,N-diethylaminoethyl methacrylate is not observed.

Oxidative Destruction of Organic Pollutants on the Polypropylene Fiber Modified by Nanodispersed Iron

This study aims to solve the problem of deep destruction of organic pollutants in industrial effluents by creating new composite materials with prescribed functional properties. This paper researches the possibility of using composites based on a polypropylene fiber under conditions of photocatalytic degradation of organic pollutants in aqueous and aqueous-organic media. Dye that are water soluble (eosin, brilliant green, rhodamine C) and fat-soluble (blue, yellow and red) have been chosen as organic contaminants. Composites based on the polypropylene fiber have been obtained by introducing nanodispersed iron onto the surface of the initial polymer, using ion implantation and super high frequency irradiation methods. The obtained composites are characterized, and their photocatalytic activity is studied with respect to the pollutants under study in the conditions of the Fenton-like system and visible radiation. The results show that the obtained composite materials are effective catalysts for oxidative photodestruction of organic dyes in aqueous and aqueous-organic media, and their decolorization degree reaches 80–100%.

Chromogenic and fluorogenic detection of selected anions by bis-terpyridine Fe(II) complex through displacement approach

Abstract This paper deals with synthesis, characterization and anion recognition properties of a homoleptic bis-terpyridine Fe(II) complex covalently coupled with diarylethene unit. The recognition event was examined in both organic as well as mixed aqueous–organic medium through different optical channels and spectroscopic techniques by taking advantage of metal–ligand interaction in the complex. The complex acts as sensor for \(\hbox {F}^{-}\), \(\hbox {OAc}^{-}\) and \(\hbox {CN}^{-}\) among the other studied anions (\(\hbox {F}^{-}\), \(\hbox {Cl}^{-}\), \(\hbox {Br}^{-}\), \(\hbox {I}^{-}\), \(\hbox {CN}^{-}\), \(\hbox {OAc}^{-}\), \(\hbox {H}_{2}\hbox {PO}_{4}^{-}\), \(\hbox {SCN}^{-}\), \(\hbox {BF}_{4}^{-}\) and \(\hbox {ClO}_{4}^{-})\) without selectivity. In contrast to acetonitrile, the complex acts as highly selective chromogenic and fluorogenic sensor for only \(\hbox {CN}^{-}\) in water. Detection limit of the metalloreceptor towards \(\hbox {CN}^{-}\) was determined from the absorption and emission titration data and the observed values lie in the order of \(10^{-9}\) M in acetonitrile and \(10^{-8}\) M in mixed aqueous–organic media.Graphical AbstractSYNOPSIS Anion sensing property of a bis-terpyridine Fe(II) complex was thoroughly investigated in both acetonitrile and water–acetonitrile (100:1, v/v) media through different optical channels and spectroscopic techniques. Interestingly, the complex acts as chromogenic and fluorogenic receptor for cyanide in predominantly aqueous medium with very low detection limit.

Nitro-imidazoles in ferrocenyl alkylation reaction. Synthesis, enantiomeric resolution and in vitro and in vivo bioeffects

Ferrocenylalkyl nitro-imidazoles (4a-h, 5a-h) were prepared via the regiospecific reaction of the α-(hydroxy)alkyl ferrocenes, FcCHR (OH) (1a–h; Fc = ferrocenyl; R = H, Me, Et, Pr, i-Pr, Ph, ortho-Cl-Ph, ortho-I-Ph), with nitro-imidazoles in aqueous organic medium (H2O-CH2Cl2) at room temperature in the presence of HBF4, within several minutes in good yields. X-ray structural data for racemic (R,S)-1-N-(benzyl ferrocenyl)-2-methyl-4-nitroimidazole (5f) were determined. The resulting enantiomers were resolved into enantiomers by analytical HPLC on modified amylose or cellulose chiral stationary phases. The viabilities of 4b, 4d, 5b, 5cin vitro, and in experiments in vivo antitumor effects of 1-N-ferrocenylethyl-4-nitroimidazole (4b) against murine solid tumor system Ca755 carcinoma were evaluated.

Ground- and Excited-State Acidity of Analogs of Red Wine Pyranoanthocyanins.

Pyranoflavylium cations are synthetic analogs containing the same basic chromophore as the pyranoanthocyanins that form in red wine during maturation and are responsible for its final color. Determination of the ground- and excited-state acidities for a series of eight substituted hydroxy pyranoflavylium cations shows that they are weak acids in the ground state (pKa ranging from 3.4 to 4.4 in aqueous buffer solution), but substantially more acidic in the first excited singlet state (pKa * ranging from ca. 0.2 to 0.7 in 30% methanol-water). Unlike the ground-state acidities, which show no obvious trend with electronic effects of the substituents, the excited-state pKa * values correlate well with Hammett sigma parameters for the substituents on the pyranoflavylium chromophore. This difference in the transmission of electronic effects between ground and excited state is reflected in the localization of the HOMO of the cation and conjugate base in distinct regions of the chromophore as compared to delocalization of the LUMO over the entire molecule. The current results provide further support for the conclusion that excited-state proton transfer is the dominant deactivation pathway for the pyranoflavylium cation excited singlet state in aqueous or aqueous-organic media and presumably for pyranoanthocyanins as well.

Ionic liquid-assisted synthesis of Pt nano thin films at toluene–water interface: Enhanced CO tolerance in methanol fuel cells and adsorptive removal of p-nitrophenol from water

In this investigation, we report a one-pot method for the synthesis of Pt/ionic liquid nano thin films at organic-aqueous media at room temperature without using any harsh conditions. Synthesized Pt/ionic liquid thin films were characterized with common analytical techniques. Transmission electron microscope images confirmed the formation of spherical particles having a size distribution in the range of 4–12 nm. Ionic liquids have a key role in the control of better size distribution and prevent from agglomeration of nanostructures by preparing a shell around particles. These catalysts were applied for the reduction of toxic p-nitrophenol into non-toxic p-aminophenol and exhibited good catalytic activity. Also, they exhibit excellent CO tolerance in methanol oxidation process of fuel cells. This method provides a novel, rapid, low cost and economical alternative for the reduction of toxic organic pollutants in water and also to prepare high quality catalysts with low metal loading for methanol fuel cells. Pt/1-aminoethyl-3-methylimidazolium bromide exhibits better CO tolerance than Pt/1-methyl-3-octylimidazolium chloride and Pt/1-methyl-3-octylimidazolium tetrafluoroborate thin films.

Fast quantification of short chain fatty acids and ketone bodies by liquid chromatography-tandem mass spectrometry after facile derivatization coupled with liquid-liquid extraction

Short chain fatty acids (SCFA) and ketone bodies recently emerged as important physiological relevant metabolites because of their association with microbiota, immunology, obesity and other metabolic states. They were commonly analyzed by GC–MS with long run time and laborious sample preparation. In this study we developed a novel LC-MS/MS method using fast derivatization coupled with liquid-liquid extraction to detect SCFA and ketone bodies in plasma and feces. Several different derivatization reagents were evaluated to compare the efficiency, the sensitivity and chromatographic separation of structural isomers. O‑benzylhydroxylamine was selected for its superior overall performance in reaction time and isomeric separation that allowed the measurement of each SCFAs and ketone bodies free from interferences. The derivatization procedure is facile and reproducible in aqueous-organic medium, which abolished the evaporation procedure hampering the analysis of volatile short chain acids. Enhancement in sensitivity remarkably improved the detection limit of SCFA and ketone bodies to sub-fmol level. This novel method was applied to quantify these metabolites in fecal and plasma samples from lean and DIO mouse.

Investigation of Chemical Stability of Dihalogenated Organotelluranes in Organic-Aqueous Media: The Protagonism of Water.

The biological activity of tellurium compounds is closely related to the tellurium oxidation state or some of their structural features. Hypervalent dihalogenated organotelluranes 1-[butyl(dichloro)-λ4-tellanyl]-2-(methoxymethyl)benzene (1a) and 1-[butyl(dibromide)-λ4-tellanyl]-2-(methoxymethyl)benzene (1b) have been described as inhibitors of proteases (cysteine and threonine) and tyrosine phosphatases. However, poor attention has been given to their physicochemical properties. Here, a detailed investigation of the stability in water of these organotelluranes is reported using 125Te NMR analysis. Dihalogenated organotelluranes 1a and 1b were both stable in DMSO- d6 (from 25 to 75 °C), demonstrating their thermal stability. However, the addition of a phosphate buffer solution (pH 2-8) to 1a or 1b resulted in an immediate conversion to a new Te species, assumed to be the corresponding telluroxide. Similar behavior was observed in pure water, demonstrating the low chemical stability of these dihalogenated species in the presence of water. These results allow concluding that previous biological activity reported for dihalogenated organotelluranes 1a and 1b could be attributed to the corresponding derivatives from the reaction with water. In the same way as for AS-101, we demonstrated that organotelluranes 1a and 1b are not stable in aqueous solution. It suggests a proactive role of these organotelluranes in previously reported biological activity.

Chromatomass-spectrometric identification of electrochemical transformation products of kresoxim-methyl in solutions

The products of electrochemical transformations of organic compounds are similar in many aspects to the products of their chemical reactions. The information on the nature and the formation mechanisms of such products is important for pesticides because this allows characterizing the mechanisms of their decomposition in the soil, aquatic environments and plants. A set of electrochemical processes involving such pesticide of the strobilurin class as kresoxim-methyl [methyl ( E )-2- methoxyimino-2-(2-( o -tolyloxymethyl)­phenyl)acetate] in its solution in aqueous organic medium [mixture of an aqueous solution of ammonium formate (pH 7.4) and acetonitrile (3: 1 v/v)] with the concentration of 100 mg/mL, and the results of chromatomass-spectrometric identification (HPLC-ESI-MS-MS) of the formed products were considered. It has been revealed that hydrolysis products predominate in the mixture of the kresoxim-methyl electrolysis products, including corresponding carboxylic acid and such demethylation products as oximes. Kresoxim-methyl oxidation products, such as the corresponding hydroxamic acid, have been detected in small amounts only. At the same time, the reduction products – amines, most likely formed from oximes, – have been identified. Keeping in mind the restricted information content of the HPLC-ESI-MS-MS method for establishing the structure of the previously uncharacterized analytes, the method of comparing the relative intensities of the peaks of reaction mixture constituents detected in the positive and negative ionization modes was used in identification of the products of electrochemical transformations. The signals of the protonated amines predominate in the first case, while in the second case the compounds containing carboxyl groups ionized at pH 7.4 are detected. Keywords: Pesticides, kresoxim-methyl, electrochemical processes, hydrolysis, oxidation and reduction, identification of products DOI: http://dx.doi.org/10.15826/analitika.2018.22.3.009 (Russian) Tatiana I. Pushkareva, Sergey S. Ermakov, Igor G. Zenkevich, St. Petersburg State University, Universitetskii prosp., 26, St. Petersburg, 198504, Russian Federation

Biosorbents based on esterified starch carrying immobilized oil-degrading microorganisms

The complex sorbents based on hydrophobized starch, which contain oil-degrading microorganisms, have been proposed for effective sorption and utilization of petroleum-related pollutants. The sorbents were made on the base of benzoic, lauric and stearic acid esters of starch with degrees of substitution of 0.4–1.1. The esterification of starch was carried out by the reaction with acyl chlorides of the corresponding acids in an aqueous-organic medium. The structure of the esters was studied by SEM, IR and NMR spectroscopy. As a result of porous hydrophobic structure, these sorbents are capable of binding and retention of petroleum products on the water surface, and keeping the flotation for at least 30days after the petroleum products sorption. The test of biodegradability of the obtained samples revealed that the modified starches can be degraded by microscopic fungi, therefore they do not cause secondary pollution. The cultures of yeast Rhodotorula glutinis VKM Y-2993D and bacteria Pseudomonas libanensis VKM B-3041D immobilized on the sorbent facilitate the rapid utilization of accumulated petroleum products.

Reactions of Criegee Intermediates with Alcohols at Air-Aqueous Interfaces.

The fate of Criegee intermediates (CIs) from the gas-phase ozonolysis of unsaturated organic compounds in the troposphere is largely controlled by their reactions with water vapor. We recently found that against all expectations carboxylic acids compete at millimolar concentrations with water for CIs at the air-liquid interface of aqueous organic media. This outcome is consistent with both the low water concentration in the outermost interfacial layers and the enrichment of the competing acids therein. Here we show, via online electrospray mass spectrometric detection, that CIs generated in situ in the fast ozonolysis of sesquiterpenes (C15H24) on the surface of water:acetonitrile microjets react with n ≥ 4 linear alcohols CnH2n+1OH to produce high molecular weight C15+n ethers in one step. The OH group of 1-octanol proved to be ∼25 times less reactive than that of n-octanoic toward CIs at the same bulk molar concentration, revealing that the reactivity of hydroxylic species depends on both acidities and interfacial affinities. CI interfacial reactions with surface-active hydroxylic species, by bypassing water, represent shortcuts to molecular complexity in atmospheric aerosols.

Anion- and Solvent-Induced Rotary Dynamics and Sensing in a Perylene Diimide [3]Catenane.

A novel dynamic [3]catenane consisting of a large four-station central macrocycle which incorporates a bay tetrachloro-functionalized perylene diimide (PDI) unit and two triazolium anion-binding motifs, mechanically bonded with two smaller isophthalamide-containing macrocycles, is constructed using an anion template synthetic methodology. Proton NMR, electronic absorption, and fluorescence emission spectroscopies together with molecular dynamics simulations are used to investigate the anion recognition- and solvent-dependent dynamic properties of the higher-order mechanically interlocked molecule. Importantly, unprecedented solvent-dependent and anion-binding-induced circumrotatory motion in a hetero[3]catenane system is demonstrated where the exotic dual rotary switching behavior provides a unique and sophisticated mechanism for optical anion sensing in competitive protic organic and aqueous-organic media.

Improved synthesis of isomaltooligosaccharides using immobilized α-glucosidase in organic-aqueous media.

α-Glucosidase was immobilized onto an epoxy-activated resin (Eupergit C) to catalyze maltose into isomaltooligosaccharides (IMO), and then the effects of organic-aqueous media on the enzymatic properties of immobilized α-glucosidase were examined. An immobilization efficiency of 79.61% was obtained under the condition of pH 6.0, ionic strength of 2.0M, and 30mg of protein/g of resin. The butyl acetate-aqueous biphasic system was found to significantly improve the catalytic activity of the immobilized enzyme and the yield of IMO. The highest yield of IMO (50.83%, w/w) was obtained at pH 4.5 and 55°C in a butyl acetate/buffer system (25:75, v/v). In addition, the immobilized enzyme particles were distributed into the organic phase after the completion of transglycosylation, which facilitates the separation and recycling use of the immobilized enzyme. Immobilized α-glucosidase retains a robust reusability in this continuous operation model. The present findings are of potential in improving the IMO manufacturing process.

Broad range ON/OFF pH sensors based on pKa tunable fluorescent BODIPYs

A set of highly fluorescent, pH-responsive boron dipyrromethene dyes covering the pH range of 5–12 is presented for broad range pH measurements in mixed aqueous-organic media and polymer matrices. Readout in the intensity domain with low cost and miniaturized instrumentation utilizes reversible protonation induced switching ON of their initially completely quenched fluorescence mediated by photoinduced electron transfer. All dyes, rationally designed to reveal closely matching absorption and emission properties, are accessible via facile two-step reactions in overall yields of up to 20%. By modifying the substitution pattern of the meso-aryl substituent, the pKa values could be fine-tuned from 6 to 11. Integration of these molecules into polymeric films by a simple mixing procedure yielded reversible and longterm stable pH sensors for naked eye detection.