Aqueous Organic Media Research Articles

Aggregation Behavior of CHR-bis(BODIPY) Bichromophores in THF-water Mixtures: Effect of Linking Positions and Aryl-spacer Substituents.

Aggregation-caused quenching effect (ACQ) greatly limits the practical use of many organic luminophores in biomedicine, optics and electronics. The comparative analysis of aggregation characteristics of CHR-bis(BODIPY) bichromophores 1-6 with R = H, Ph, MeOPh and various linking positions (α,α-; α,β-; β,β- and β',β'-) in THF-water mixtures with different water fractions or dye concentrations is first presented in this article. Both the linking style 1-4 and the arylation of the spacer with phenyl (Ph-) 5 or methoxyphenyl (MeOPh-) 6 substituents strongly affect the formation of luminophore aggregated forms in binary THF-water mixtures. The α,α-and β,β-isomers (1 and 3) form non-fluorescent H-type aggregates in THF-water mixtures with fw > 70%. The α,β-; β',β'-isomers (2, 4) and the MeOPh-substituted β,β-bichromophore 6 are characterized by predominant formation fluorescent aggregates. All bichromophores are characterized by the presence of residual amounts of non-aggregated forms in binary mixtures with maximum water content. The results are useful for controlling the aggregation behavior and spectral characteristics of CHR-bis(BODIPY) bichromophores in aqueous-organic media, which is important in the development of biomarkers and PDT agents.

Effect of Organic Solvents on the Activity, Stability and Secondary Structure of asclepain cI, Using FTIR and Molecular Dynamics Simulations.

The present study aims at understanding the effect of organic solvents on the specific proteolytic activity and operational stability of asclepain cI in aqueous-organic media, using correlations between geometrical and structural parameters of asclepain cI. These correlations were determined by molecular dynamics (MD) simulations and the secondary structure of the enzyme validated by Fourier-transform Infrared (FTIR) spectroscopy. Asclepain cI exhibited significantly higher catalytic potential in 29 of the 42 aqueous-organic media tested, composed by 0.1mM TRIS hydrochloride buffer pH 8 (TCB) and an organic solvent, than in buffer alone. Asclepain cI in water-organic miscible systems showed high FTIR spectral similarity with that obtained in TCB, while in immiscible systems the enzyme acquired different secondary structures than in buffer. Among the conditions studied, asclepain cI showed the highest catalytic potential in 50% v/v ethyl acetate in TCB. According to MD simulations, that medium elicited solvation and flexibility changes around the active center of asclepain cI and conducted to a new secondary structure with the active center preserved. These results provide valuable insights into the elucidation of the molecular mechanism of asclepain cI tolerance to organic solvents and pave the way for its future application for the synthesis of peptides in aqueous-organic media.

Organo NHC catalyzed aqueous synthesis of 4β-isoxazole-podophyllotoxins: in vitro anticancer, caspase activation, tubulin polymerization inhibition and molecular docking studies.

We present, for the first time, the organo-N-heterocyclic carbene (NHC) catalyzed 1,3-dipolar cycloaddition of 4β-O-propargyl podophyllotoxin (1) with in situ aromatic nitrile oxides to afford regioselective 4β-isoxazolepodophyllotoxin hybrids (6a-n) in benign aqueous-organic media. Preliminary anticancer activity results showed that compound 6e displayed superior activity against MCF-7, HeLa and MIA PaCa2 human cell lines compared with podophyllotoxin. Compounds 6j and 6n showed greater activity against the MCF-7 cell line than the positive control. Caspase activation studies revealed that compound 6e at 20 μg ml-1 concentration had greater caspase 3/7 activation in MCF-7 and MIAPaCa2 cells than podophyllotoxin. Furthermore, in vitro tubulin polymerization inhibition studies revealed that compound 6e showed comparable activity with podophyllotoxin. Finally, in silico molecular docking studies of compounds 6e, 6j, 6n and podophyllotoxin on α,β-tubulin (pdb id 1SA0) revealed that compound 6n showed excellent binding energies and inhibition constants compared with podophyllotoxin.

Halogen bonding BODIPY-appended pillar[5]arene for the optical sensing of dicarboxylates and a chemical warfare agent simulant.

A pillar[5]arene host, functionalised with halogen bonding (XB) recognition sites and BODIPY fluorophores, demonstrates strong binding and optical sensing of environmentally relevant dicarboxylates and a chemical warfare agent simulant, in organic and competitive aqueous-organic media - enabled by the unprecedented combination of fluorophore-conjugated XB interactions with the hydrophobic pillar[5]arene host cavity.

Highly efficient one pot electrocatalytic method for transforming alcohols to nitriles

A one pot electrocatalytic method was developed for the oxidative transformation of alcohols into nitriles in a two-phase aqueous-organic medium: methylene chloride-aqueous sodium bicarbonate solution. Under the proposed conditions, the catalytic system 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl-pyridine base with the participation of ammonium iodide makes it possible to convert a wide range of alcohols into nitriles with good to excellent yields (81-99%) without the use of catalysts based on toxic metals, hazardous reagents and/or oxidizing agents. In the synthesis, ammonium iodide is simultaneously a source of nitrogen and iodine, and also functions as a component of the background electrolyte.

Exploring organo-bentonite adsorption properties for biphenyl removal from organic-aqueous media: kinetic study and industrial perspective

Biphenyl, a frequently encountered and resilient compound in wastewater, proves resistant to conventional treatment methods because of its enduring nature. It forms the structural basis for persistent organic pollutants such as PCBs. In this study, we explored the adsorption of biphenyl in an organo-aqueous medium using both natural (Bent) and organomodified (CTAB-Bent) bentonite clay. Our objective was to highlight its potential for biphenyl wastewater treatment. We analyzed the physicochemical and textural properties of these clays through FTIR, XRF, XRD, SEM, BET method, and Zeta potential measurements. Impressively, these materials exhibited remarkable biphenyl adsorption capacity under acidic conditions, with Bent achieving 60% removal and CTAB-Bent an impressive 91%. We investigated the adsorption kinetics using first-order and pseudo-second-order models and assessed isotherm data with the Langmuir, Freundlich, and Langmuir-Freundlich (sips) equations. The Langmuir model, at pH 3, proved optimal, with high accuracy (R²) and minimal error (RMSE) values (0.997 and 1.20, respectively). Clay nature significantly influenced pollutant uptake efficiency, confirming the efficacy of the selected bio-based clay. We propose a protocol adaptable for industrial-scale applications.

Evolution of Organic Solvent-Resistant DNA Polymerases.

The introduction of thermostable polymerases revolutionized the polymerase chain reaction (PCR) and biotechnology. However, many GC-rich genes cannot be PCR-amplified with high efficiency in water, irrespective of temperature. Although polar organic cosolvents can enhance nucleic acid polymerization and amplification by destabilizing duplex DNA and secondary structures, nature has not selected for the evolution of solvent-tolerant polymerase enzymes. Here, we used ultrahigh-throughput droplet-based selection and deep sequencing along with computational free-energy and binding affinity calculations to evolve Taq polymerase to generate enzymes that are both stable and highly active in the presence of organic cosolvents, resulting in up to 10% solvent resistance and over 100-fold increase in stability at 97.5 °C in the presence of 1,4-butanediol, as well as tolerance to up to 10 times higher concentrations of the potent cosolvents sulfolane and 2-pyrrolidone. Using these polymerases, we successfully amplified a broad spectrum of GC-rich templates containing regions with over 90% GC content, including templates recalcitrant to amplification with existing polymerases, even in the presence of cosolvents. We also demonstrated dramatically reduced GC bias in the amplification of genes with widely varying GC content in quantitative polymerase chain reaction (qPCR). By expanding the scope of solvent systems compatible with nucleic acid polymerization, these organic solvent-resistant polymerases enable a dramatic reduction of sequence bias not achievable through thermal resistance alone, with significant implications for a wide range of applications including sequencing and synthetic biology in mixed aqueous-organic media.

Complexes of polyvinylpyrrolidone and polyethylene glycol with palladium(II) ions: characterization and catalytic activity

In this work, we obtained complexes by mixing aqueous solution of palladium(II) chloride with polyvinylpyrrolidone and polyethylene glycol. The composition of the complex compounds was determined by potentiometric and conductometric titration. IR spectroscopy and scanning electron microscopy (SEM) confirmed the coordination of polymeric ligand to palladium and allowed evaluating the morphology and features of the complex surface. The catalytic activity of the synthesized compounds in the oxidation of octene-1 by inorganic oxidizers (NaBrO3, K2S2O8) in aqueous-organic media in dimethyl sulfoxide (DMSO) under mild conditions was calculated. The reaction product was octanone-2, obtained in good yield (62–98%). Quantitative analysis of octanone-2 was made by the gas-chromatographic method. Mass spectrometry confirms the formation of octanone-2. The complexes are able to participate in five consecutive catalytic cycles without significant loss of catalytic efficiency. Oxidation of octene-1 proceeds by the oxidation-reduction mechanism and consists of two key stages.

Thermodynamic functions of succinic acid in acetone–water binary mixtures based on computation of KI & KII constants

Succinic acid is commonly used in various chemical, pharmaceutical, environmental and industrial activities and its reactivity is principally determined by the pK(I & II) values. Therefore, the dissociation constants of succinic acid have been determined in this study on the basis of emf measurements in both different acetone mole fractions and temperature range. The pK(I or II) values of the studied acids in acetone aqueous media were found higher than those obtained in other organic aqueous media with the same conditions (temperature and mole fraction of solvent). Moreover, (KI/KII) in 40 wt% acetone–water mixture was identified to follow succinic acid < malic acid < malonic acid < maleic acid owing to the stabilization of intramolecular hydrogen bonding. The free energy of transfer (ΔG0I or II) for succinic acid was increased with the increasing of pKI or pKII values due to the decrease in relative permittivity (εr) via increment of the acetone fraction in the aqueous medium. The trend of ΔS°I value among the studied acids were found to follow maleic < malic < succinic < malonic. ΔS°II values were characterized lower than ΔS°I due to possible solvent interactions with the acid anion (L2-). Therefore, ΔH°II values of the second dissociation process were identified lower than ΔH°I to favor an exothermic reaction.

Impact of organic solvents on the catalytic performance of halohydrin dehalogenase

Biocatalytic transformations in organic synthesis often require the use of organic solvents to improve substrate solubility and promote the product formation. Halohydrin dehalogenases (HHDHs) are enzymes that catalyze the formation and conversion of epoxides, important synthetic class of compounds that are often sparingly soluble in water and prone to hydrolysis. In this study, the activity, stability, and enantioselectivity of HHDH from Agrobacterium radiobacter AD1 (HheC) in form of cell-free extract were evaluated in various aqueous-organic media. A correlation was discovered between the enzyme activity in the ring-closure reaction and logP of the solvent. Knowledge of such a relationship makes biocatalysis with organic solvents more predictable, which may reduce the need to experiment with a variety of solvents in the future. The results revealed a high enzyme compatibility with hydrophobic solvents (e.g., n-heptane) in terms of activity and stability. Regarding the HHDH applicability in an organic medium, inhibitions by a number of solvents (e.g., THF, toluene, chloroform) proved to be a more challenging problem than the protein stability, especially in the ring-opening reaction, thus suggesting which solvents should be avoided. In addition, solvent tolerance of the thermostable variant ISM-4 was also evaluated, revealing increased stability and to a lesser extent enantioselectivity compared to the wild-type. This is the first time such a systematic analysis has been reported, giving insight into the behavior of HHDHs in nonconventional media and opening new opportunities for the future biocatalytic applications. KEY POINTS: • HheC performs better in the presence of hydrophobic than hydrophilic solvents. • Enzyme activity in the PNSHH ring-closure reaction is a function of the logP. • Thermostability of ISM-4 variant is accompanied by superior solvent tolerance.

Solvothermal Synthesis of Calcium Hydroxyapatite via Hydrolysis of Alpha-Tricalcium Phosphate in the Presence of Different Organic Additives

In this study, the effects of sodium lauryl sulfate and various amino acids (DL-aspartic acid, dodecanedioic acid, and suberic acid) on the formation of calcium-deficient hydroxyapatite via hydrolysis of α-tricalcium phosphate (α-TCP) were investigated; moreover, a combined effect of these additives and ethylene glycol as a synthesis medium was also estimated. The hydrolysis reaction was performed in solutions containing different concentrations of additives in aqueous and mixed aqueous–organic media under solvothermal conditions. It was demonstrated that the nature and the concentration of organic additives influence the phase purity and morphology of the final product. Higher concentrations of sodium lauryl sulfate and dodecanedioic acid induced the formation of impurities in addition to hydroxyapatite, while aspartic and suberic acid did not affect the phase purity. The morphology of the samples varied from plate- to rod-like depending on the concentrations of specific organic additive.

Intracellular Zn(II) induced turn-on fluorescence of an L-phenylalanine-derived pseudopeptide.

A C2 symmetric L-phenylalanine-derived pseudopeptide has been synthesized for selective and sensitive recognition of Zn(II) ions in aqueous-organic media. The pseudopeptidic probes exhibit intracellular Zn(II) ion-sensing capabilities as demonstrated via live-cell fluorescence studies on RAW264.7 cells. Hence, we present a bioinspired pseudopeptide for potential biological applications involving intracellular Zn(II) ion detection.

A molecular chemodosimeter to probe "closed shell" ions in kidney cells.

Two quinidine-functionalized coumarin molecular probes have been synthesized and have been found to bind metal cations (Cd2+, Co2+, Cu2+, Fe2+, Hg2+, Ni2+, and Zn2+) with high affinity in organic-aqueous media (DMSO-HEPES). The chemodosimeters coordinate with the Zn2+ ions in a two-to-one ratio (molecular probe : Zn2+) with a log β of 10.0 M-2. Upon the addition of the closed-shell metal ions studied, a fluorescence turn-on via an excimer formation is seen at 542 nm due to the quinaldine moiety adopting a syn arrangement when coordinated to the metal Zn2+ ions. Confocal microscopy monitored free Zn2+ ions in the Human Embryonic Kidney cell line HEK293 by coordinating with the chemodosimter.

Synthesis and high sensitivity Al3+ recognition of fluorescent probe molecule based on pincer bis‐N‐heterocyclic carbene

Two bis-(Nitrogen-Heterocyclic Carbene, NHC) derivatives, 1, 3-bis[1-(quinolin-8-yl)-imidazolium-3-yl)]-benzene bis-hexafluorophosphate (2a), 2, 5-bis[1-(quinolin-8-yl)-imidazolium-3-yl)]-pyridine bis-hexafluorophosphate (2b), were synthesized, and characterized by 1H NMR and 13C NMR spectra and X-ray single crystal diffraction. The bis-NHC 2a was demonstrated as an excellent fluorescence chemo-sensor molecule for selectively recognition of Al3+ ion in aqueous-organic media. Its pyridine analogue molecule 2b haven't selectivity recognition character to metal ions with the fluorescence enhancement for most metal ions. A 1:1 binding ratio and strong supramolecular interaction between Al3+ ion and the carbonic hydrogen and quinoline nitrogen were suggested by Job's plot analysis and 1HNMR spectroscopy titrations of Al3+ ion and 2a. The detection limit for Al3+ ion was calculated to be 0.32 µM. The practical application in tap water samples has been evaluated, which reveals the potential applications of bis-NHC 2a in complicated environments.

Anti-Hofmeister Anion Selectivity via a Mechanical Bond Effect in Neutral Halogen-Bonding [2]Rotaxanes.

Exceptionally strong halogen bonding (XB) donor-chloride interactions are exploited for the chloride anion template synthesis of neutral XB [2]rotaxane host systems which contain perfluoroaryl-functionalised axle components, including a remarkably potent novel 4,6-dinitro-1,3-bis-iodotriazole motif. Halide anion recognition properties in aqueous-organic media, determined via extensive 1 H NMR halide anion titration experiments, reveal the rotaxane host systems exhibit dramatically enhanced affinities for hydrophilic Cl- and Br- , but conversely diminished affinities for hydrophobic I- , relative to their non-interlocked axle counterparts. Crucially, this mechanical bond effect induces a binding selectivity which directly opposes Hofmeister bias. Free-energy analysis of this mechanical bond enhancement demonstrates anion recognition by neutral XB interlocked host systems as a rare and general strategy to engineer anti-Hofmeister bias anion selectivity in synthetic receptor design.

Peculiarities of γ-Al2O3 Crystallization on the Surface of h-BN Particles.

The main goal of the present work was to synthesize a composite consisting of h-BN particles coated with a γ-Al2O3 nanolayer. A method was proposed for applying nanocrystalline γ-Al2O3 to h-BN particles using a sol-gel technique, which ensures the chemical homogeneity of the composite at the nano level. It has been determined that during crystallization on the h-BN surface, the proportion of spinel in alumina decreases from 40 wt.% in pure γ-Al2O3 to 30 wt.% as a result of the involvement of the B3+ ions from the surface nitride monolayers into the transition complex. For comparison, nano-alumina was synthesized from the same sol under the same conditions as the composite. The characterization of the obtained nanostructured powders was carried out using TEM and XRD. A mechanism is proposed for the formation of a nanostructured γ-Al2O3@h-BN composite during the interaction of Al-containing sol and h-BN suspension in aqueous organic media. The resulting composite is a promising model of powdered raw materials for the development of fine-grained ceramic materials for a wide range of applications.

Stability of Terpenoid-Derived Secondary Ozonides in Aqueous Organic Media

1,2,4-Trioxolanes, known as secondary ozonides (SOZs), are key products of ozonolysis of biogenic terpenoids. Functionalized terpenoid-derived SOZs are readily taken up into atmospheric aerosols; however, their condensed-phase fates remain unknown. Here, we report the results of a time-dependent mass spectrometric investigation into the liquid-phase fates of C10 and C13 SOZs synthesized by ozonolysis of a C10 monoterpene alcohol (α-terpineol) in water:acetone (1:1 = vol:vol) mixtures. Isomerization of Criegee intermediates and bimolecular reaction of Criegee intermediates with acetone produced C10 and C13 SOZs, respectively, which were detected as their Na+-adducts by positive-ion electrospray mass spectrometry. Use of CD3COCD3, D2O, and H218O solvents enabled identification of three types of C13 SOZs (aldehyde, ketone, and lactol) and other products. These SOZs were surprisingly stable in water:acetone (1:1) mixtures at T = 298 K, with some persisting for at least a week. Theoretical calculations supported the high stability of the lactol-type C13 SOZ formed from the aldehyde-type C13 SOZ via intramolecular rearrangement. The present results suggest that terpenoid-derived SOZs can persist in atmospheric condensed phases, potentially until they are delivered to the epithelial lining fluid of the pulmonary alveoli via inhaled particulate matter, where they may exert hitherto unrecognized adverse health effects.

Polymer-metal complex based on copper(II) acetate and polyvinyl alcohol: thermodynamic and catalytic properties

In this work we obtained a polymer-metal complex by mixing aqueous solution of copper(II) acetate with PVA at a certain ratio, pH of the solution and temperature. The composition of the complex compound was determined by potentiometric and conductometric titration. The possibility of a complex formation was proved by calculating thermodynamic characteristics. The stability constant of the polymer-metal complex was calculated on the basis of the modified Bjerrum’s method. The metal-polymer complex was synthesized in the ratio 1:2. IR spectroscopy and scanning electron microscopy (SEM) confirmed the coordination of polymeric PVA ligand to copper and allowed evaluating the morphology and features of the complex surface. The catalytic activity of the synthesized compound was evaluated in the oxidation reaction of elemental phosphorus (P4) by oxygen in aqueous-organic media under mild conditions. Quantitative analysis of phosphoric acid was made by photocolorimetric method. We found that the oxidation process of P4 in the presence of the complex Cu(PVA)2(OAc)2 in aqueous-organic media is characterized with the maximum absorption rate, in comparison with Cu(OAc)2·H2O oxidation process with P4, and yields up to 97% of the products. The process of oxidation of yellow phosphorus by oxygen in the presence of the copper(II)-PVA complex proceeds through key reactions of two-electron reduction of the catalyst P4 with the formation of intermediate phosphorus-containing products P3+ and the stages of catalyst regeneration by oxygen. Twenty-electron oxidation of P4 to the phosphorus-containing P5+ products involves 10 two-electron redox reactions and a number of complexation or hydrolysis stages.

Design and synthesis of a novel azo-Schiff base ligand: Its application as a colorimetric chemosensor for selective detection of Ni2+ and CN– in aqueous-organic media, computational studies, antimicrobial properties, and molecular logic circuits

In this study, an azo-Schiff base ligand was synthesized and then investigated using different analyses. The synthesized ligand as a colorimetric chemosensor was able to detect CN– and Ni2+ based upon the color changes from colorless to yellow. The limit of detection (LOD) for CN– and Ni2+ was determined at 2.19 × 10-6 M and 7.14 × 10-7 M, respectively. By DFT method, the boundary orbitals and energy gaps between them were determined. Using the TD-DFT method, the electronic transitions in the DMSO solvent were then simulated, which agreed with the experimental findings. This ligand revealed antibacterial activity against Staphylococcus aureus bacteria. Practically, this chemosensor functioned as a colorimetric test strip for Ni2+. Furthermore, chemosensor L was applied to detect CN– in apple seeds. By applying CN− (input 1) and Ni2+ (input 2) as chemical inputs and the absorption intensity signal as outputs at particular wavelengths of the chemosensor L, various logic functions such as (AND, OR, XNOR, NOR, INHIBT, IMPLICATION and XOR) were constructed. The chemosensor L could function as a half-subtractror by utilizing optical inputs. The complementary OR/NOR, IMP/INH and XOR/XNOR circuits were elaborated by employing two inputs.

Proton-Catalyzed Decomposition of Multifunctionalized Organic Hydroperoxides Derived from the Reactions of Criegee Intermediates with Ethylene Glycol in Aqueous Organic Media

Organic hydroperoxides (ROOHs) are ubiquitous, reactive oxygen species that play central roles in atmospheric, environmental, and biological chemistry. Because atmospheric ROOHs possess not only −OOH but in most cases other functionalities such as −C(═O) and −OH, they are expected to reside in condensed phases such as aerosols, fog and cloud droplets, and wet films of leaves and soils. Here, we report a study of the kinetics of the liquid-phase decomposition of multifunctionalized C12 α-alkoxyalkyl hydroperoxides (α-AHs) that possessed an ether, a carbonyl, a hydroperoxide, and two hydroxy groups. We derived the rate coefficients (k) from single exponential decays of the α-AH signal in water/ethylene glycol solutions acidified by acids found in the atmosphere. Our discovery that the k of the decomposition of the α-AHs increased exponentially from pH 5.1 to 3.9 but independently of the properties of the acid provided firm evidence that the decomposition was catalyzed by H+. The temperature dependence of k and an Arrhenius plot yielded an activation energy (Ea) of 15.0 ± 0.3 kcal mol–1 for the decomposition of C12 α-AHs in solution. The proposed H+-catalyzed decomposition of ROOHs may be a general process that provides H2O2 and multifunctionalized compounds to atmospheric condensed phases that are acidic in nature.