Search Results (509)

The sustainable recovery of valuable metals such as Cu and Co from ores is a pressing need considering environmental and economic challenges. Therefore, this study evaluates the effectiveness of deep eutectic solvents (DESs) as alternative leaching agents for Cu and Co extraction. Four DESs were prepared using choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and oxalic acid (OA), ethylene glycol (EG), urea (U) and thiourea (TU) as hydrogen bond donors (HBDs). Leaching experiments were conducted with DESs supplemented with 30 wt.% water at varying temperatures, various solid-to-liquid ratios, and time durations. The ChCl:OA DES demonstrated the highest leaching efficiencies among the DESs tested on pure CuO and CoO, achieving 89.2% for Cu and 92.4% for Co (60 °C, 400 rpm, 6 h, −75 + 53 µm particle size, and 1:10 solid-to-liquid ratio). In addition, the dissolution kinetics, analysed using the shrinking core model (SCM), showed that the leaching process was mainly controlled by surface chemical reactions. The activation energy values for Cu and Co leaching were 46.8 kJ mol⁻¹ and 51.4 kJ mol⁻¹, respectively, supporting a surface chemical control mechanism. The results highlight the potential of ChCl:OA as a sustainable alternative for metal recovery. Full article

The paper proposes a putative prebiotic scenario leading to homochirality in the RNA world. In this scenario, racemic ribose, the only chiral moiety in RNA, was enantioseparated (in its pyranose form) on a chiral surface formed by the adsorption of (prochiral) nucleobases (NBs) on a mineral or metal. Purine bases (adenine and guanine) are more likely candidates for this process than pyrimidine bases because they have more H-bond donors and acceptors. Another possible candidate surface for the enantioseparation of ribose would be formed by the adsorption of nucleobase pairs, e.g., guanine–cytosine (GC). Interactions of ribose molecules with hydrogen bond donors and acceptors of NBs or NB pairs (located on the surface) enforced the orientation of ribose molecules in two directions perpendicular to each other and parallel to the surface. Consequently, the energy of interactions of enantiomers of the sugar with the surface was not the same. Thus, a solvent moving along the surface caused the enantiomers of ribose to move with different rates, resulting in the enantioseparation of ribose in a chromatography-like process. The same process would also separate ribose from other monosaccharides in the mix. Hydrogen bonding between nucleobases was also pivotal in the formation of large homochiral domains on the surfaces. Full article

In this study, we present the preparation and characterization of a novel thallium(I) coordination compound of the polyether ionophorous antibiotic salinomycin (SalH). The complex [TlSal(H₂O)] exists as two subunits, SalTl1 and SalTl2, which differ slightly in their structural parameters. Salinomycin acts in a pentadentate coordination mode through oxygen donor atoms, and the six-fold arrangement around the metal centers is completed by interaction with a water molecule. In the overall complex structure, the two mononuclear species SalTl1 and SalTl2 are connected via a hydrogen bond network by a third water molecule. The inclusion of the heavy metal ion into the structure of the polyether ionophore reduces its biological activity against Gram-positive microorganisms and cervical cancer cells at in vitro conditions. Full article

We report on the preparation and characterization of a new family of hydrogen-bonded nematogenic liquid crystalline dimers. The dimers are supramolecular complexes that consist of a benzoic acid derivative, acting as the proton donor, featuring a spacer with seven methylene groups and a terminal decyloxy chain, paired with an azopyridine derivative as the proton acceptor. The latter was either fluorinated or nonfluorinated with variable alkoxy chain length. The formation of a hydrogen bond between the individual components was confirmed using FTIR and ¹H NMR spectroscopy. All supramolecules were investigated for their liquid crystalline behaviour via a polarized optical microscope (POM) and differential scanning calorimetry (DSC). All materials exhibit enantiotropic nematic phases as confirmed by X-ray diffraction (XRD) and POM investigations. The nematic phase range depends strongly on the degree and position of fluorine atoms. Additionally, the supramolecules demonstrated a rapid and reversible transition between the liquid crystal phase and the isotropic liquid state because of trans-cis photoisomerization upon light irradiation. Therefore, this study presents a straightforward approach to design photo-responsive nematic materials, which could be of interest for nonlinear optics applications. Full article

The limited understanding of intermolecular interactions in deep eutectic solvents (DESs) has restricted their rational design and broader application. In this study, a series of hydrophobic DESs (HDESs) were prepared using lidocaine as the hydrogen bond acceptor and various carboxylic acids as hydrogen bond donors. Their physicochemical properties, including density, viscosity, and thermal stability, were systematically characterized. Interactions between components were evaluated through excess molar volume, viscosity deviation, and Grunberg–Nissan parameters. Strong hydrogen bonding between lidocaine and carboxylic acids was confirmed, which weakened with increasing alkyl chain length of the acids. Furthermore, as the acid content in the mixture increased, lidocaine’s ability to disrupt the intrinsic hydrogen-bonding network of the carboxylic acids decreased, thereby weakening the hydrogen bonding interactions between the components. The extraction capability of the HDESs for cobalt ions was evaluated in aqueous systems. Cobalt, a key material in lithium-ion batteries and advanced alloys, is in rising demand due to clean energy development. The lidocaine/decanoic acid (1:2) system exhibited nearly 100% extraction efficiency, surpassing conventional extractants. The hydrophobic nature of the HDESs facilitated effective phase separation and reduced solvent loss. These findings provide theoretical insights and design principles for developing high performance HDESs tailored for environmentally friendly metal recovery, particularly in battery recycling and treatment of industrial wastewater. Full article

Transition metal (II) complexes stabilized by 2,6-di(pyrazol-3-yl)pyridine as a novel coplanar tridentate nitrogen-donor ligand have been reported for their unusual structures and photoluminescent properties. In this work, the ligand 2,6-bis(5-isopropyl-1H-pyrazole-3-yl)pyridine (denoted as L) and its transition metal (II) halogenido complexes viz [ZnCl₂(L)] (1), [ZnBr₂(L)] (2), [CuCl₂(L)] (3), and [CuCl(L)(thf)](PF₆) (4) were synthesized and characterized by single crystal X-ray crystal analysis. Its structures contained N–H groups in its pyrazole rings and hydrogen bonds between these N–H donors and the coordinated halogenide ions and lattice solvent molecules. Tautomers between 3-pyridyl and 5-pyridyl substitutes were also observed. In L, the N–H group at the pyrazole nitrogen was located adjacent to the pyridine ring to form hydrogen bonds with adjacent pyrazoles. However, on complexation, the H atoms at the pyrazole nitrogens are shifted remotely to the pyridine. The zinc (II) complexes [ZnCl₂(L)] (1) and [ZnBr₂(L)] (2) possessed distorted trigonal pyramidal structures in the solid state. By comparison, the copper (II) complexes [CuCl₂(L)] (3) and [CuCl(L)(thf)](PF₆) (4) adopted square pyramidal geometry with a Jahn–Teller distortion resulting from their d⁹ electron configurations. Full article

Polymer electrolytes (PEs) provide enhanced safety for high–energy–density lithium metal batteries (LMBs), yet their practical application is hampered by intrinsically low ionic conductivity and insufficient electrochemical stability, primarily stemming from suboptimal Li⁺ solvation environments and transport pathways coupled with slow polymer dynamics. Herein, we demonstrate a molecular design strategy to overcome these limitations by regulating the Li⁺ solvation structure through the synergistic interplay of conventional Lewis acid–base coordination and engineered hydrogen bond (H–bond) networks, achieved by incorporating specific H–bond donor functionalities (N,N′–methylenebis(acrylamide), MBA) into the polymer architecture. Computational modeling confirms that the introduced H–bonds effectively modulate the Li⁺ coordination environment, promote salt dissociation, and create favorable pathways for faster ion transport decoupled from polymer chain motion. Experimentally, the resultant polymer electrolyte (MFE, based on MBA) enables exceptionally stable Li metal cycling in symmetric cells (>4000 h at 0.1 mA cm⁻²), endows LFP|MFE|Li cells with long–term stability, achieving 81.0% capacity retention after 1400 cycles, and confers NCM622|MFE|Li cells with cycling endurance, maintaining 81.0% capacity retention after 800 cycles under a high voltage of 4.3 V at room temperature. This study underscores a potent molecular engineering strategy, leveraging synergistic hydrogen bonding and Lewis acid–base interactions to rationally tailor the Li⁺ solvation structure and unlock efficient ion transport in polymer electrolytes, paving a promising path towards high–performance solid–state lithium metal batteries. Full article

Natural deep eutectic solvents (NaDESs) are emerging solvents for their yield when used for extraction of different molecules, including polyphenols. NaDESs are a cutting-edge technology that offers numerous advantages, including cheap cost, safety, effectiveness and environmental friendliness. However, due to NaDES’ high boiling point, the recovery and separation of compounds after the extraction is the bottleneck of the process. In this work, two affordable methods were tested for the recovery of phenolic compounds from three binary NaDESs (composed of choline chloride mixed separately with lactic acid, tartaric acid or glycerol as hydrogen bond donors): the antisolvent and the liquid–liquid extraction methods. The former was assessed by diluting the extracts with different aliquots of water, employed as antisolvent, which was ineffective. For the liquid–liquid extraction method, ethyl acetate (EtOAc), acetonitrile (ACN), 2-chlorobutane (2-CB) and 2-methyltetrahydrofuran (2-MeTHF) were compared. Except for ACN, all solvents were perfectly immiscible with the three NaDESs, forming biphasic systems that were analyzed by colorimetric assays and HPLC/MS. 2-MeTHF applied on a 10-fold water dilution of the NaDES extract reached recovery percentages higher than 90% for most of the non-anthocyanin phenols and good recovery (up to 80%) for some anthocyanins. 2-MeTHF appears to be the first known solvent capable of extracting anthocyanins from NaDESs. Finally, a two-step liquid–liquid extraction performed firstly with EtOAc and subsequently with 2-MeTHF is proposed for the separation of different phenolic fractions. Full article

Representatives of the hexasubstituted benzene derivatives, also known as hexa-hosts, have been the subject of extensive studies in solution and in the solid state, including the investigation of their ability to act as artificial receptors for various substrates, as well as detailed conformational analyses. In this paper, we describe the X-ray crystal structure of hexakis(acetoxymethyl)benzene (1), a member of the above class of compounds. The molecules of 1 adopt an aaabbb conformation, in which three side-arms point to the same face of the central benzene ring, while the other three point in the opposite direction. As the compound lacks strong hydrogen bond donors, C–H···O hydrogen bonds connect the molecules to a three-dimensional supramolecular network. According to the Hirshfeld surface analysis, the H∙∙∙O/O∙∙∙H interactions represent the major contribution of the molecular Hirshfeld surface. Full article

Substantial in vitro experimental data have been produced about the safety, antioxidant, neuro- and hepatoprotective effects of a series of recently synthesized N-pyrrolyl hydrazide-hydrazones (compounds 5, 5a–5g). However, compound activity across multiple assays varies and it is challenging to elucidate the favorable physicochemical characteristics of the studied compounds and guide further lead optimization. The aim of the current study is to apply exploratory data analysis in order to profile the biological effects of the novel hydrazide-hydrazones, gain insights related to their mechanisms of action in the context of in silico predictions and identify key predictor–outcome relationships. We collected a dataset from available in vitro studies of compounds 5, 5a–5g. It included cytotoxicity values, protection against hydrogen peroxide-induced damage in HepG2 and SH-SY5Y cells, two radical scavenging assays and a hemolysis assay across a range of treatment concentrations. SwissADME-based predictions of chemometric and ADME parameters and pro-oxidant enzyme docking data were generated to provide context for the interpretation of in vitro outcome patterns and identify causal relationships. Multiple factor analysis (MFA), followed by hierarchical clustering on principal components (HCPC), was applied to profile compounds’ biological behavior. This revealed that differences in the number of H-bond donors, in the permeability coefficient and in the docking scores to two pro-oxidant enzymes could aid in explaining the effects of compounds with similar in vitro profiles. HCPC differentiated 5a as mostly neuroprotective, 5 and 5d as hepatoprotective radical scavengers, 5g with higher docking affinity to 5-lipoxygenase (5-LOX) and myeloperoxidase (MPO) and 5b, 5c and 5f as having less H-bond donors and variable in vitro activity. The consensus application of three variable selection approaches based on standard lasso regression, robust penalized regression and random forest confirmed the relationships between some in vitro outcomes and LogP, pan-assay interference (PAINS) alerts, 5-LOX allosteric site docking and H-bond donor numbers. The exploratory analysis of the combined in vitro and in silico dataset provides useful insights which could help explain the major drivers behind the experimental results. It can be informative in the design of new, improved members of the series of novel N-pyrrolyl hydrazide-hydrazones with better neuroprotective potential and less side effects. Full article

Multifunctional self-healing supramolecular structural toughened resins, formulated to counteract the insulating properties of epoxy polymers and integrating auto-repair mechanisms, are morphologically and spectroscopically characterized using Tunneling Atomic Force Microscopy (TUNA) and Fourier transform infrared spectroscopy (FT-IR), respectively. Specifically, the multifunctional resin comprises self-healing molecular fillers and electrically conductive carbon nanotubes (CNTs) embedded in the matrix. The selected self-healing molecules can form non-covalent bonds with the hydroxyl (OH) and carbonyl (C=O) groups of the toughened epoxy matrix through their H-bonding donor and acceptor sites. An FT-IR analysis has been conducted to evaluate the interactions that the barbiturate acid derivatives, serving as self-healing fillers, can form with the constituent parts of the toughened epoxy blend. Tunneling Atomic Force Microscopy (TUNA) highlights the morphological characteristics of CNTs, their dispersion within the polymeric matrix, and their affinity for the globular rubber domains. The TUNA technique maps the samples’ electrical conductivity at micro- and nanoscale spatial domains. Detecting electrical currents reveals supramolecular networks, determined by hydrogen bonds, within the samples, showcasing the morphological features of the sample containing an embedded conductive nanofiller in the hosting matrix. Full article

Nuclear factor-κB (NF-κB) signaling plays a pivotal role in regulating immune responses and is strongly implicated in cancer progression and inflammation-related diseases. The inhibitory κB kinases (IKKs), particularly IKKα, are central to modulating NF-κB activity, with distinct roles in the canonical and non-canonical signaling pathways. This study investigates the potential of selectively targeting IKKα to develop novel therapeutic strategies. A receptor–ligand interaction pharmacophore model was generated based on the co-crystallized structure of IKKα, incorporating six key features, two hydrogen bond acceptors, two hydrogen bond donors, one hydrophobic region, and one hydrophobic aromatic region. This model was used to virtually screen a diverse natural compound library of 5540 molecules, yielding 82 candidates that matched the essential pharmacophore features. Molecular docking and molecular dynamics simulations were subsequently employed to evaluate binding conformations, stability, and dynamic behavior of the top hits. The end-state free energy calculations (gmx_MMPBSA) further validated the interaction strength and stability of selected compounds. To experimentally confirm their inhibitory potential, key compounds were tested in LPS-stimulated RAW 264.7 cells, where they significantly reduced IκBα phosphorylation. These findings validate the integrative computational-experimental approach and identify promising natural compounds as selective IKKα inhibitors for further therapeutic development in cancer and inflammatory diseases. Full article

In this work, we present a study on the thermal/transport properties of a novel deep eutectic solvent (DES) obtained by using N-methyltrifluoroacetamide (FNMA) as the hydrogen bond donor (HBD) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the hydrogen bond acceptor (HBA). The binary phase diagram, thermal stability, flammability, viscosity and ionic conductivity of the as-prepared DESs were investigated at atmospheric pressure. The binary phase diagram shows a range of eutectic molar ratios (x_LiTFSI = 0.2~0.33), with the lowest deep eutectic temperature of −84 °C. At x_LiTFSI = 0.2 (i.e., FNMA:LiTFSI = 4:1 and denoted as DES-4:1). The as-prepared DES composition exhibits high thermal stability (onset temperature of weight loss = 78 °C), a low viscosity (η = 48.9 mPa s at 25 °C), relatively high ionic conductivity (σ = 0.86 mS cm⁻¹ at 25 °C) and non-flammability. The transport properties, including ionic conductivity and viscosity, as a function of temperature are in accordance with the Vogel–Fulcher–Tammann (VFT) equations. With increasing molar ratio of HBD vs. HBA, the viscosity decreases, and the ionic conductivity increases at a given temperature between 25 °C and 80 °C. The roughly equal pseudo-activation energies for ion transport and viscous flow in each composition imply a strong coupling of ion transport and viscous flow. Walden plots indicate vehicular transport as the main ion transport mechanism for the DES-4:1 and DES-3:1 compositions; meanwhile, it was confirmed that the ionic conductivity and viscous flow are strictly coupled. The present work is expected to provide strategies for the development of wide-temperature-range and safer electrolytes with low salt concentrations. Full article

Deep eutectic solvents (DESs) are environmentally friendly solvents formed by combining hydrogen bond donors and acceptors, resulting in a eutectic mixture with a lower melting point than the individual components. While there is extensive research on the electrochemical synthesis of platinum nanoparticles in DESs, to the best of our knowledge, there are no studies on the chemical reactivity of platinum(II) complexes in these systems. This study investigates the simple model reaction between K₂PtCl₄ and ethylenediamine (en), exploring the behaviour in DES environment, to optimize the synthesis of simple cisplatin-like platinum compounds with the potential objective of improving the traditional methods, decreasing the number of steps required for obtaining target compounds and reducing chemical waste. The reactions were performed in two hydrophilic DESs: choline chloride:glycerol 1:2 (glyceline, GL) and choline chloride:ethylene glycol 1:2 (ethaline, EG). The experiments, conducted in a 70% (v/v) DES and 30% 1:1 H₂O/D₂O mixture to allow for direct NMR analysis, revealed that en quickly formed [PtCl₂(en)], which further reacted to produce [Pt(en)₂]Cl₂. Reaction products were characterised by 1D (¹H and ¹⁹⁵Pt{¹H}) and 2D ([¹H,¹³C]-HSQC and [¹H,¹⁵N]-HSQC) NMR experiments. The discolouration of solutions, due to the consumption of K₂PtCl₄, and the precipitation of the purple Magnus salt [Pt(en)₂][PtCl₄] occurred over time. The main observed difference between the two solvent mixtures was the slower reactivity in glyceline, due to the much higher viscosity of the solution. Diffusion-ordered spectroscopy (DOSY) indicated lower water mobility in DES mixtures than pure water, with the reaction products closely associated with DES molecules. Full article

This work is a continuation of our recent work on the prediction of hydrogen-bonding (HB) interaction enthalpies. In the present work, a simple method is proposed for the prediction of the HB interaction free energies. Quantum chemical (QC) calculations are combined with the Linear Solvation Energy Relationship (LSER) approach for the determination of novel QC-LSER molecular descriptors and the development of the method. Each hydrogen-bonded molecule is characterized by an acidity or proton donor capacity, ${\alpha }_G$, and/or a basicity or proton acceptor capacity, ${\beta }_G$. These descriptors suffice for the prediction of HB interaction free energy when the interacting molecules possess one acidic and or one basic site. In this case of two interacting molecules, 1 and 2, their overall HB interaction free energy is $c\left({\alpha }_{G1}{\beta }_{G2}+{\beta }_{G1}{\alpha }_{G2}\right)$, where c is a universal constant equal to (ln10)RT = 5.71 kJ/mol at 25 °C. This holds true over the full composition range, that is, regardless of which molecule is solute and which solvent. In the case of complex multi-sited molecules possessing more than one distant acidic site and/or more than one type of distant basic sites, two sets of ${\alpha }_G$ and ${\beta }_G$ descriptors are needed, one for the molecule as solute in any solvent and one for the same molecule as the solvent of any solute. Descriptors ${\alpha }_G$ and ${\beta }_G$ are reported for a number of common hydrogen-bonded molecules but they may be obtained for any other hydrogen-bonded molecule of interest from its molecular surface charge distribution already available or easily obtained via relatively cheap DFT/basis-set QC calculations. The new predictive scheme is validated against corresponding estimations of the widely used Abraham’s LSER model. The developments in the present work and the previous one are useful for solvation studies in chemical and biochemical systems and, particularly, for equation-of-state developments in molecular thermodynamics. The strengths and limitations of the new predictive method are critically discussed. Full article