Polar Solvents Research Articles

Disclosing the mechanism of uranium(VI) solvent extraction by polydentate ligands in a polar solvent: The role of ion pairs

Uranium is a key element in nuclear power. Developing new extraction systems for its purification and concentration is an important task for improving the nuclear fuel cycle. In this work solvent extraction and uranyl complexes with tri-dentate pyridine-based and tetra-dentate phenanthroline-based diphosphonates were studied in thorough detail, both in the organic phase and the solid state. A combination of experimental methods (loading isotherms and conductivity measurements), spectroscopic techniques (UV–vis, EXAFS, 31P NMR, and Raman spectroscopy) and theoretical calculations were used to disclose the mechanism of U(VI) solvent extraction. We demonstrated that with tetradentate phenanthroline-based ligands, tight ion pairs ([UO2LNO3]+[UO2(NO3)3]−) are formed. With tridentate ligands, U(VI) forms a mixture of complexes with different stoichiometries. Significant differences in the structure of complexes with tridentate ligands in the solid state compared to complexes in the organic solution were also shown.

Carbon dots with high brightness and stability towards efficient Cr(Ⅵ) and l-arginine sensors

To create fluorescent sensors for Cr (VI) and l-arginine detection, blue-emitting carbon dots (CDs, named as M-CDs) were prepared via a solvothermal synthesis by using m-phenylenediamine. The introduction of sulfuric acid changed the blue-emitting of CDs into green-emitting (named as S-CDs), in which the photoluminescence (PL) peak wavelengths of samples M-CDs and S-CDs were 450 and 540 nm, while their PL efficiencies were 21.7 and 84.2 % respectively. Sulfuric acid resulted in the average fluorescent lifetime of the CDs was prolonged into 8.19 from 4.65 ns. The photo and thermal stable tests demonstrated that theses CDs revealed excellent stability. Meanwhile, CDs flexible films with bright blue- and green-emitting were prepared utilizing the favorable solubility of CDs in polar solvents. Mono-dispersed CDs as luminescent materials demonstrated it promising prospects in luminescent devices field. Furthermore, M-CDs exhibited excellent selectivity towards Cr(Ⅵ) and l-arginine. The detected limit (0.86 μM for Cr(Ⅵ) and 0.43 μM for l-arginine) was determined by assessing the response of M-CDs to various concentrations of Cr(Ⅵ) ion and l-arginine solutions. These bright CDs revealed great potential for accurate detection of Cr(Ⅵ) and l-arginine.

Modified Microwave-assisted Solid-liquid Halex Reaction using Phosphonium Salt as Efficient and Robust Phase Transfer Catalyst

: A modified solid-liquid halex reaction was developed in the presence of a robust phase transfer catalyst under microwave conditions. A fast, mild, and practical microwave- assisted synthesis of 2,3-difluoro-5-chloropyridine 3 starting from 2,3,5- trichlorpyridine 1 and spray-dried KF in polar aprotic solvent was developed. The addition of Tetrakis (piperidino) phosphonium chloride as phase transfer catalyst A was studied under microwave irritation (450W) and increased the yield and significantly reduced the reaction time in contrast to the conventional heating procedure. The highest reaction rate was observed at 5 wt% phase transfer phosphonium salt catalyst to 2,3,5-trichloropyridine 1.

Green synthesis of lignin-based non-isocyanate polyurethanes as reusable, self-healable and removable adhesives

Lignin-based non-isocyanate polyurethanes (LNIPUs) represent a class of polymers synthesized from lignin—an abundant, renewable polymer found in the cell walls of plants—without the use of toxic isocyanates. This makes LNIPUs an eco-friendly alternative to traditional petroleum-based polyurethanes. Despite their advantages, the synthesis of LNIPUs often entails complex processes, the use of additional catalysts, and highly polar solvents, which largely restrict their accessibility and practical applications. In this study, we present an higly efficient, catalyst-free, and solvent-free methodology for synthesizing LNIPUs. A series of novel LNIPUs were successfully prepared through a one-pot, catalyst-free and solvent-free polymerization reaction involving aminated fractionated lignin (ALFE) and bis(6-membered cyclic carbonate) (6CC). We systematically investigated the properties of the resulting LNIPUs, with a particular focus on the adhesion performance. The incorporation of ALFE significantly enhanced the adhesive properties of the resultant LNIPUs on aluminum, wood, and plastic substrates, achieving a maximum bonding strength of 3.09 MPa on aluminum. Furthermore, LNIPUs exhibit exceptional functionalities, including reusability, self-healing capabilities, and removability, along with improved thermal stability and photothermal properties.

Side-Chain Engineering of Boron β-Dialdiminate Homopolymer for Solvent-Dependent Emission Properties.

Luminescent materials that respond to changes in microscopic chemical conditions are essential for visualizing and evaluating molecular environments. Boron complexes are often employed as robust scaffolds for constructing such responsive systems because of their inherent stimuli-responsive properties. However, in the case of nonresponsive luminophores, the absence of these intrinsic features limits their range of applications. In this study, environment-responsive luminescent homopolymers based on the boron β-dialdiminate complex are developed, which is intrinsically less responsive, by introducing optimized side chains. As a key finding, the triethylene glycol-decorated polymer exhibits more intense luminescence in chloroform but weaker luminescence in N,N-dimethylformamide. Structural analyses using NMR and size-exclusion chromatography suggest that this polymer forms larger aggregates in polar solvents because of the solvophobicity of its main chain, while the polar side chains assist in maintaining adequate dispersibility of these aggregates. Photophysical measurements indicate that interchromophore interactions within the aggregates should be responsible for the reduced luminescence in polar solvents. These findings suggest that side-chain engineering should be an effective strategy for creating stimuli-responsive polymers from otherwise nonresponsive luminophores.

Revealing the antioxidant properties of alkyl gallates: a novel approach through quantum chemical calculations and molecular docking.

This study investigates the antioxidant potential of alkyl gallates (C1-C10), focusing on the impact of alkyl chain length and solvent polarity on their antioxidant properties. Known for their biomedical relevance in mitigating oxidative stress, alkyl gallates' structure-activity relationships, particularly regarding chain length and environmental factors, still need to be explored. Key thermochemical parameters, including bond dissociation enthalpy (BDE), ionization potential (IP), proton affinity (PA), and electron transfer enthalpy (ETE), reveal that shorter alkyl chains (C1-C4) exhibit superior antioxidant activity. In contrast, longer chains (C5-C10) show reduced effectiveness due to steric hindrance and lower solubility in polar solvents. Molecular docking studies also demonstrated favorable binding interactions with vital biological targets, further reinforcing their antioxidant potential. Quantum chemical calculations were performed using Gaussian 16 with the B3LYP/6-311G(dp) basis set for geometry optimizations. Solvent effects were modeled using the integral equation formalism-polarized continuum model (IEF-PCM). Molecular docking studies were conducted using AutoDockTools 4.2, targeting Tyrosine Kinase Hck, Heme Oxygenase, and Human Serum Albumin to evaluate fundamental binding interactions. These computational methods provided insights into alkyl gallates' chemical reactivity and antioxidant efficiency, allowing for the rational design of more potent antioxidant compounds.

Cation-lone pair interaction in Alkali/alkaline earth metal ion-heavier borazine analogue complexes.

The present study is the first report on the formation of alkali/alkaline earth metal ion-heavier borazine analogue complexes via cation-lone pair interaction. Density functional calculations are performed in scrutinizing the complex formation between alkali (Li+, Na+, K+)/alkaline earth (Be2+, Mg2+, Ca2+) metal ions and heavier borazine analogues (HBA) viz. B3P3H6, Al3N3H6, Al3P3H6, Al3As3H6, and Ga3P3-H6. The complexes are found to be stable in gas phase with stabilization energies within the range 26.40 to 324.74 kcalmol-1. The stability can be attributed to the polarizing power of the involved metal ions. Presence of solvent phase exerted notable impact on the stability of the complexes; stability is reduced significantly with the increase in solvent polarity. The process of complexation is exothermic and spontaneous. QTAIM analysis indicated the presence of both ionic and covalent interaction between HBAs and metal ions. HOMO energy, Wiberg bond index, NCI-isosurface and RDG plot analysis revealed the major role of cation-lone pair interaction in the complexation process.

Aminocarbonyl Fluorophores with a Strong Emissive Inverted Solvatochromism.

Three aminocarbonyls were synthesized, and their emissive spectral behavior recorded at various solvent polarities showed marked inverted solvatofluorochromism. The emission energy inversion occurs at moderate solvent polarities and was found to be triggered by a change in the solute-solvent interaction responsible for the stabilization of the highly zwitterionic excited state of the dyes, from dipolarity to acidity.

Nile Red Fluorescence: Where's the Twist?

Nile Red is a fluorescent dye used extensively in bioimaging due to its strong solvatochromism. The photophysics underpinning Nile Red's fluorescence has been disputed for decades, with some studies claiming that the dye fluoresces from two excited states and/or that the main emissive state is twisted and intramolecular charge-transfer (ICT) in character as opposed to planar ICT (PICT). To resolve these long-standing questions, a combined experimental and theoretical study was used to unravel the mechanism of Nile Red's fluorescence. Time-resolved fluorescence measurements indicated that Nile Red emission occurs from a single excited state. Theoretical calculations revealed no evidence for a low-lying TICT state, with the S1 minimum corresponding to a PICT state. Ultrafast pump-probe spectroscopic data contained no signatures associated with an additional excited state involved in the fluorescence decay of Nile Red. Collectively, these data in polar and nonpolar solvents refute dual fluorescence in Nile Red and definitively demonstrate that emission occurs from a PICT state.

Understanding the relationship between preferential interactions of peptides in water-acetonitrile mixtures with protein-solvent contact surface area.

The influence of polar, water-miscible organic solvents (POS) on protein structure, stability, and functional activity is a subject of significant interest and complexity. This study examines the effects of acetonitrile (ACN), a semipolar, aprotic solvent, on the solvation properties of blocked Ace-Gly-X-Gly-Nme tripeptides (where Ace and Nme stands for acetyl and N-methyl amide groups respectively and X is any amino acid) through extensive molecular dynamics simulations. Individual simulations were conducted for each peptide, encompassing five different ACN concentrations within the range of χACN = 0.1-0.9. The preferential solvation parameter (Γ) calculated using the Kirkwood-Buff integral method was used for the assessment of peptide interactions with water/ACN. Additionally, weighted Voronoi tessellation was applied to obtain a three-way data set containing four time-averaged contact surface area types between peptide atoms and water/ACN atoms. A mathematical technique known as N-way Partial Least Squares (NPLS) was utilized to anticipate the preferential interactions between peptides and water/ACN from the contact surface areas. Furthermore, the temperature dependency of peptide-solvent interactions was investigated using a subset of 10 amino acids representing a range of hydrophobicities. MD simulations were conducted at five temperatures, spanning from 283 to 343K, with subsequent analysis of data focusing on both preferential solvation and peptide-solvent contact surface areas. The results demonstrate the efficacy of utilizing contact surface areas between the peptide and solvent constituents for successfully predicting preferential interactions in water/ACN mixtures across various ACN concentrations and temperatures.

Donor–Acceptor Type Solvatochromic Flavonoid Materials Fluorphores for Polarity Sensing and Real‐Time Temperature Monitoring

AbstractElectron donor–acceptor (D–A) molecules are emerging tools for designing sensitive luminogens, attracting significant research attention. However, due to poor quantum yields under certain conditions, current D–A fluorophores often suffer from fluorescence quenching in practical applications. Developing new D–A dyes and functional composites is crucial for expanding their applications. Here, a novel donor–acceptor type flavonoid dye molecule, namely “AFL”, exhibiting both polarity‐dependent fluorescence emission wavelength shift and viscosity‐dependent intensity change, for polarity measurement and temperature sensing is designed and synthesized. Because the intramolecular charge transfer (ICT) can be enhanced by a decrease of excited state energy caused in high‐polarity organic solvents, AFL undergoes fluorescence emission wavelength shift that shows fluorescence color response to solvents of different polarities and hence differentiates between them. Moreover, the actual temperature can be monitored by the as‐designed AFL@tetradecanoic acid (AFL@TA) sensor. By combining with TA, viscosity sensitively changes upon the temperature change of insoluble composites, thus realizing the fluorescence intensity response to temperature. Remarkable recyclable performance and satisfactory mechanical properties are integrated. This study provides a promising approach to developing a new D–A fluorescent probe and furnishes perspectives on the potential of such D–A type flavonoid material in stimuli‐responsive systems with a focus on visualization sensing technology.

Interfacially Cross-Linked Polydopamine/Polybenzimidazole Composite Membranes for Organic Solvent Nanofiltration.

Interfacial cross-linking was used to prepare composite organic solvent nanofiltration (OSN) membranes comprising a polydopamine (PDA) active layer formed on a polybenzimidazole (PBI) substrate. Dibromo-p-xylene (DBX) was employed as a cross-linking agent to make the composite membranes chemically stable against harsh polar aprotic solvents. The interfacial cross-linking of PDA/PBI allowed for finely tuning the molecular weight cutoff (MWCO) of the membrane, resulting in a membrane with precise molecular separation capabilities for OSN. The morphology and surface properties of the membranes were characterized, and a membrane with a MWCO of 286 Da was investigated for OSN of a series of solvents. The membrane permeance was in the order of acetonitrile (MeCN) > methanol (MeOH) > acetone > toluene > dimethylformamide (DMF) > heptane > ethanol (EtOH) > isopropanol (IPA) > tetrahydrofuran (THF). The membranes displayed a sharp pore size distribution, yielding a rejection rate of over 99% for Rose Bengal (RB, MW 1020 g/mol) and Remazol brilliant blue (RBB, MW 626.5 g/mol) from DMF and EtOH solutions. When it came to methyl orange (MO, MW 327.3 g/mol) that had a molecular weight closer to the MWCO of the membrane, the membrane still displayed a high rejection rate of 95% and 99% in nanofiltrating solvents DMF and EtOH, respectively. In addition, it was demonstrated that the membrane was able to effectively fractionate mixed solutes having molecular weights appropriate for the MWCO rating of the membrane during OSN.

Polarity Gradient Solvent Confinement Membrane Cartridge to Broaden Metabolite Coverage of Plasma Untargeted Analysis.

Various polarity chemicals exist in complex samples, such as plasma; nontargeted comprehensive analysis naturally requires multiple polar-extracted solvents; consequently, the polarity of the solvent plays a crucial role in the extraction efficiency of analytes from complex samples. In the present study, based on the diffusion behavior and nanoconfinement effect of solvents in the nanoconfined space, the polarity gradient solvent confinement liquid-phase nanoextraction (PGSC-NLPNE) protocol aimed to perform a one-step nontargeted analysis of a wide range of metabolites in plasma was established. The continuously wide range of extracted solvent polarities on carbon nanofibers/carbon fiber (CNFs/CF) membranes was achieved using a mixture of hexane, dichloromethane, methanol, and water as nanoconfined solvents. The polarities (Log P) of gradient solvents ranged from -1.38 to 3.94. Correlational analyses indicated that metabolites with Log P values ranging from -1.90 to 3.84 were closely related according to similarity-intermiscibility theory. Coupled with a homemade modified guard column device, CNFs/CF membrane cartridge (CCMC), a PGSC-NLPNE-UHPLC-MS online protocol was established and applied in plasma untargeted analysis. By comparing metabolome coverage, reproducibility, and extraction recovery with protein precipitation and two-step liquid-liquid extraction commonly used in untargeted analysis, the PGSC-NLPNE-CCMC protocol demonstrated higher reproducibility and recovery. This protocol has shown great potential for ultrafast analysis of plasma untargeted metabolomics with broader metabolome coverage. It could be a potential tool to rapidly screen out valuable biomarkers related to diseases in the clinic.

Proximity Effects and Aggregation of Hamilton-Receptor Barbiturate Host-Guest Complexes Probed by Cross-Metathesis and ESI MS Analysis.

The molecular environment around supramolecular bonding systems significantly affects their stability and the assembly of host-guest complexes, most prominent for hydrogen bonds (H-bonds). Hamilton receptor-barbiturate host-guest complexes are well-known in solution, typically forming a 1:1 molar ratio complex. However, within a polymer matrix, these complexes can form higher-order assemblies, deviating from the standard 1:1 complex, which are challenging to characterize and often require lab-intensive methods. In this study, a novel Hamilton receptor (H) was equipped with cyclopentene moieties and used as a host to form host-guest complexes (H-B) with allobarbital (B), followed by covalent crosslinking. UV-Vis spectroscopy titration experiments in different solvents and at various temperatures revealed that polar solvents containing additional H-bonding sites significantly reduce the formation of the 1:1 H-B complex, as indicated by a reduced association constant. Higher-order aggregates (HH-dimer, HHH-trimer) were subsequently detected via an alkene cross-metathesis (CM) reaction to fix the assemblies covalently, followed by analysis via electrospray ionization mass spectrometry (ESI MS). This two-step method, firstly via CM fixation followed by ESI MS, was extended to study the H-B model complex within a polyisobutylene (PIB) matrix, presenting a direct method to analyze the complex host-guest assembly in solvent-free (polymer) environments.

Static-spun mesoporous silica-coated CsPbBr3 blue fibres: synthesis and fluorescence properties.

Due to their excellent properties, blue CsPbBr3 quantum dots show great promise for full-colour display and lighting applications. This study used acetonitrile, a polar solvent, to post-treat CsPbBr3 quantum dots, resulting in a blue shift to 453nm. To enhance stability, these quantum dots were encapsulated within the pore structure of mesoporous silica. A flexible luminescent fiber material was prepared using poly (lactic acid) (PLA) as the substrate, demonstrating improved hydrophobicity and stable optical properties. The material exhibited a contact angle of 99.7° and maintained 82.2% of its fluorescence intensity after 30days at room temperature. These findings highlight its significant potential for optical applications.

Functions of a Complex Variable with a Large Parameter and Construction of Regions

The paper describes an experimental setup for studying the solubility of substances in SCF media and the implementation of a supercritical fluid extraction process using a pure and modified polar solvent additive. The advantages and disadvantages of this installation are analyzed, ways of improving it are indicated, leading to achieving a more accurate GFR flow rate, maintaining the necessary constant pressure in the first extract collector for fractionation of a certain component of the mixture and eliminating multiple regulation of the GFR flow rate.

Parameter Dependency of Electrochemical Reduction of CO2 in Acetonitrile - A Data Driven Approach.

The electrochemical CO2 reduction reaction (CO2RR) is a promising technology for the utilization of captured CO2. Though systems using aqueous electrolytes is the state-of-the-art, CO2RR in aprotic solvents are a promising alternative that can avoid the parallel hydrogen evolution reaction (HER). While system parameters, such as electrolyte composition, electrode material, and applied potential are known to influence the reaction mechanism, there is a lack of intuitive understanding as to how. We show that by using multivariate data analysis on a large dataset collected from the literature, namely random forest modelling, the most important system parameters can be isolated for each possible product. We find that water content, current density, and applied potential are powerful determinants in the reaction pathway, and therefore in the Faradaic efficiency of CO2RR products.

Correction: X-ray structures, thermal stabilities and kinetics of guest desolvation of complexes of three fluorenone-derived host compounds with the polar aprotic guest solvent, tetramethylurea

Correction: X-ray structures, thermal stabilities and kinetics of guest desolvation of complexes of three fluorenone-derived host compounds with the polar aprotic guest solvent, tetramethylurea

A Versatile Method for Preparation of BrCOFs Aerogels and Efficient Functionalization via Suzuki-Miyaura Reaction.

Covalent organic frameworks (COFs) aerogels solve the restrictions on processability and application caused by the insolubility and non-fusibility of powders while avoiding the inaccessibility of pore structures by dense stacking. At the current start-up stage where COFs aerogels are scarce and difficult to synthesize, design of generalized synthetic methods play an indispensable role in guiding and developing COFs aerogels. Moreover, evolving the functionality of COF aerogels is equal vital, which achieves higher performance and broader practical applications. In this work, for the first time, processable BrCOFs aerogels have been synthesized without vacuum by seven kind polar solvents, which realizes general preparation of BrCOFs aerogels. It is extremely friendly to the inapplicability for some scenarios. Furthermore, by Suzuki-Miyaura cross-coupling reaction, BrCOFs aerogels are endows with cyano groups (-CN), trifluoromethyl (-CF3) and methyl sulfonyl (-SO2-CH3) efficiently. As a proof-of-concept, BrCOFs-SO2-CH3 aerogels served as a quasi-solid electrolyte for lithium-metal batteries (LMBs), which effectively enhance the performance of batteries.

Synthesis and Structure Identification of 1-[4-(4-pentylcyclohexyl)-phenyl]-3-(quinolin-8-ylamino)prop-2-en-1-one Molecules in Solvents of Different Polarities

Synthesis and Structure Identification of 1-[4-(4-pentylcyclohexyl)-phenyl]-3-(quinolin-8-ylamino)prop-2-en-1-one Molecules in Solvents of Different Polarities