Reaction Solvent Research Articles

Markov State Model of Solvent Features Reveals Water Dynamics in Protein-Peptide Binding.

In this work, we investigate the role of solvent in the binding reaction of the p53 transactivation domain (TAD) peptide to its receptor MDM2. Previously, our group generated 831 μs of explicit-solvent aggregate molecular simulation trajectory data for the MDM2-p53 peptide binding reaction using large-scale distributed computing and subsequently built a Markov State Model (MSM) of the binding reaction (Zhou et al. 2017). Here, we perform a tICA analysis and construct an MSM with similar hyperparameters while using only solvent-based structural features. We find a remarkably similar landscape but accelerated implied timescales for the slowest motions. The solvent shells contributing most to the first tICA eigenvector are those centered on Lys24 and Thr18 of the p53 TAD peptide in the range of 3-6 Å. Important solvent shells were visualized to reveal solvation and desolvation transitions along the peptide-protein binding trajectories. Our results provide a solvent-centric view of the hydrophobic effect in action for a realistic peptide-protein binding scenario.

Enhancement of dieckol extraction yield from Ecklonia cava through optimization of major variables in generally recognized as safe solvent-based process

Ecklonia cava (EC), an edible brown macroalga abundant in intertidal areas of East Asia (Korea, Japan, and China), contains high-value bioactive compounds such as dieckol, which has antifungal, anti-inflammatory, antitumor, and antihyperlipidemic activities. However, no studies have been reported on the utilization of EC as a biorefinery feedstock, and the design of a more economical and high-yield process is required for the utilization of dieckol for the human healthcare industry. In this study, we designed a bioprocess for the high-yield recovery of dieckol from EC in a generally recognized as safe (GRAS) solvent to facilitate its application in the food and healthcare industries. Preliminary studies identified ethanol as an efficient solvent with the highest dieckol extraction yield (2.9 mg/g biomass). In order to maximize the recovery of dieckol from EC, the major extraction variables (solvent concentration, reaction temperature, and reaction time) were optimized based on statistical methods. Based on the predictive model, the numerical optimization determined that the solution with the highest dieckol content per weight of extract (62.6 vol% ethanol concentration, 54.2°C temperature, 13.2 min) was the optimal extraction condition. Under the determined conditions, the dieckol yield from EC achieved 6.4 mg dieckol/g EC (95.5% agreement with the predicted value). The designed process offers several advantages, including improving the utilization feasibility of EC, utilizing GRAS solvents with potential human applications, short extraction time (13.2 min), maximized process yield, and the highest dieckol recovery compared to previous reports.

Upcycling of Poly(lactic acid) Waste: A Valuable Strategy to Obtain Ionic Liquids.

With the aim to investigate new strategies for upcycling of plastic waste, we performed aminolysis of poly(lactic acid) (PLA), using N,N-dimethylethylenediamine (DMEDA), N,N-dimethylpropylenediamine (DMPDA), and 3-aminopropylimidazole (API) as nucleophiles. The N-substituted lactamides obtained were alkylated by using alkyl halides differing in alkyl chain length, obtaining organic salts that in most cases behaved as ionic liquids (ILs). Both aminolysis of PLA and alkylation of amides were carried out taking into consideration the basic principles of the holistic approach to green chemistry, applied at a laboratory scale, and carefully selecting the nature of the reaction solvent, temperature range, and amount of reagents. Organic salts obtained from the alkylation of N-substituted lactamides were investigated to determine their glass or solid-liquid transitions and their thermal stability. Furthermore, cytotoxicity toward normal lung fibroblasts was also assessed. Data collected show that the proposed strategy represents a valuable protocol to upcycle plastic waste, using it as starting material to obtain alternative solvents of potential industrial relevance.

Synthesis, optical characteristics and thermal stability of Mn4+-doped Na3GaF6 red-emitting phosphor for high-performance warm WLED

Nowadays, Mn4+-activated fluoride red phosphors with high color purity, strong zero phonon line emission and relatively short decay time are crucial for improving the optical performance of WLED and emerging applications. In this work, a series of red-emitting Mn4+-activated fluoride phosphors in consideration of the non-equivalent substitution of Mn4+ for Ga3+ in the Na3GaF6 host are synthesized via the coprecipitation method at room temperature. The use of different reaction solvents successfully regulates the morphology, size and luminescence intensity of the phosphor. Under blue light excitation, Na3GaF6:Mn4+ sample shows a bright narrow-band red emission with exceptional correlated color temperature (4029 K). Moreover, the emission of strong zero phonon line induces the outstanding color purity of red light (93%). In addition, the critical concentration of Mn4+ is determined to be 0.04 and the concentration quenching mechanism is also systematically discussed. Noticeably, when Na3GaF6:Mn4+ phosphor achieves maximum fluorescence emission, its fluorescence lifetime value is only 3.48 ms. Additionally, the theoretical calculated results demonstrate that Na3GaF6 host can provide strong crystal field strength for Mn4+, and the Racah parameters (B and C) and nephelauxetic ratio (β1) are used to evaluate the nephelauxetic effect of Mn4+, which is compared with other types of Mn4+-activated phosphors. The activation energy, chromaticity shift and chromaticity coordinate variation are systematically calculated to analyze the thermal stability of Na3GaF6:Mn4+ red phosphor. Meanwhile, by employing the as-prepared phosphor Na3GaF6:Mn4+ as a red component, a high-performance warm WLED shows a full spectrum emission, and the corresponding cold white light emission is also transformed into the warm white light emission (CCT = 4224 K, Ra = 89.1 and LE = 111.72 lm/W). Moreover, under high driving current, such WLED exhibits stable output light efficiency. These results suggest that Na3GaF6:Mn4+ as red phosphor has a stupendous potential for warm WLED in indoor lighting.

Molecular Precursor Approach to Sulfur-Free CuInSe2: Replacing Thiol Coordination in Soluble Metal Complexes.

Solution-processed CuInSe2 films have generally relied on sulfide or sulfoselenide precursor films that, during the grain growth process, hamper the growth of thicker films and lead to the formation of a fine-grain layer. However, recent research has indicated that sulfur reduction in the precursor film modifies the grain growth mechanism and may enable the fabrication of thicker absorbers that are free of any fine-grain layer. In this work, we pursue direct solution deposition of sulfur-free CuInSe2 films from the molecular precursor approach. To this end, we tune the amine-thiol reactive solvent system and study the changes to the resulting soluble complexes through a combination of analytical techniques. We show that by reactively dissolving indium(III) selenide and selenium in solutions of n-butylamine and 1,2-ethanedithiol, a metal thiolate species is formed, and that this metal thiolate can be modified by isolation from the thiol-containing solvent via precipitation. As the quantity of selenium in the ink increases, the thiol content in the complex decreases, eventually producing soluble [InSex]- species. Extending this method to be used with copper selenide as a copper source, molecular precursor inks can be made for solution-processed, sulfur-free CuInSe2 films. We then show that these CuInSe2 precursor films can be fully coarsened without a fine-grain layer formation, even at the desired thicknesses of 2 μm and greater.

Synergistic Induction of Solvent and Ligand-Substitution in Single-Crystal to Single-Crystal Transformations toward a MOF with Photocatalytic Dye Degradation.

External-stimuli responsiveness as found in natural organisms and smart materials is attractive for functional materials scientists who attempt to design and imitate fascinating behavior into their materials. Herein, we report a couple of new solvent-responsive isostructural two-dimensional cationic metal-organic frameworks (MOFs) of Mn(II) (1a) and Zn(II) (2a) that undergo unprecedented single-crystal to single-crystal (SCSC) transformation toward the corresponding isostructural three-dimensional MOFs of Mn(II) (1b) and Zn(II) (2b). The 2D MOFs 1a and 2a have been effortlessly and rapidly synthesized via the microwave-heating technique. The SCSC transformations are synergistically induced by solvent and ligand-substitution reactions and able to be triggered by water, methanol, ethanol, and n-propanol. Time-dependent SCSC transformations were studied by in situ X-ray diffraction. Investigations on photodegradation of methyl orange showed that Zn-MOF 2b has higher efficiency than Mn-MOF 1b under UV-C irradiation at 300 min, 94.27%, and 21.91%, respectively. The influence of charge on the dye molecules, heterogeneity of the catalysis, and •OH radical-scavenging test was studied. First-principles computations suggest that the high photocatalytic activity of 2b may be attributed to its suitable band-edge position for redox reactions.

CuNPs@Al2O3-cellulose composite for the ligand-free Suzuki cross-coupling reactions in batch and continuous flow process

In the present work, we synthesized recyclable CuNPs@Al2O3-CELL composite from an inexpensive and commercially available synthetic reagent by a simple method. The catalyst was characterized by various techniques such as TGA (Thermogravimetric analysis), SEM (Scanning electron microscope), TEM (Transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), EDS (Energy dispersive spectroscopy), and AAS (Atomic Absorption Spectroscopy). The composite was applied for the Suzuki coupling reactions in the batch and flow process. The aryl halides were easily coupled with arylboronic acids in 95 % ethanol at 78 °C. We systematically investigated the role of reaction temperature, solvent, and catalyst loading, on the transient and steady-state behavior of the flow reactor through an automated flow chemistry platform. The CuNPs@Al2O3-CELL catalytic particles demonstrate minimal deactivation and leaching over a continuous Suzuki coupling reaction at a 20 min nominal residence time at 100 °C. Moreover, the catalyst can be recovered by simple filtration and reused at least five times with a moderate decrease in product yield. The excellent activity and stability of the catalyst have been attributed to the strong chelation of the Cu species with hydroxyl functional groups of the Al2O3-CELL composite. The catalytic system was highly efficient in Suzuki coupling of various aryl bromides with different aryl boronic acids, yielding good to excellent product yields (80–96 %) with a TON of 15.914–19.066 and TOF of 2.649–9.533 h−1.

Facile synthesis of functionalized polysiloxanes with nonconventional fluorescence by oxa-Michael addition reaction

ABSTRACTDeveloping a novel methodology for the synthesis of functionalized polysiloxanes is highly desirable because of their extensive applications in engineering, textile, construction, electronics, and medical systems. Herein we introduce the oxa-Michael addition reaction as an efficient methodology to prepare a series of functionalized polysiloxanes from hydroxyalkyl-containing polysiloxanes and vinyl monomers using phosphazene base as the catalyst. The effects of various factors, including reaction time, feed ratio and solvent, were explored in this reaction. It was found that the reaction can be carried out under mild reaction (room temperature in 6 h to 24 h) with moderate to high conversion yields (60% to 99%). In particular, vinyl monomers with strong electron-withdrawing groups (e.g., cyano and sulfone groups) have higher reactivity, and the functionalized polysiloxanes can be obtained quantitatively or near-quantitatively. Interestingly, their molecular weights determined by gel permeation chromatography (GPC) reveal that the Si-O-Si skeletons were attacked by phosphazene base and re-arranged during the reaction, thus leading to improved molecular weights and more uniform molecular weight distributions in the final products than the original polysiloxanes. Moreover, these polysiloxanes exhibited intriguing nonconventional fluorescence due to the presence of unique chromophores, and those containing cyano and sulfone groups particularly exhibit the best fluorescence performance. More organosilicon materials could be developed under this simple strategy.

Facile Synthesis of a Multifunctional SnO2 Nanoparticles/Nanosheets Composite for Dye-Sensitized Solar Cells.

Synthesizing SnO2 composite nanostructures via a facile one-step method has been proven to be a great challenge. By adjusting operating variables, such as the reaction solution's pH and solvent type, several SnO2 nanostructures, in particular, a function-matching SnO2 hybrid structure composed of irregular zero-dimensional nanoparticles (NPs) and two-dimensional nanosheets (NSs), could be created. The as-prepared SnO2 composites were then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), and diffuse reflectance spectroscopy (DRS) to determine their physical properties. Dye-sensitized solar cells (DSCs) constructed with the resultant multifunctional SnO2 NPs/NSs composite exhibited the highest overall power conversion efficiency (PCE) of 5.16% among all products with a corresponding short-circuit current density of 18.6 mA/cm2 and an open-circuit voltage of 0.626 V. The improved performance can be attributed to the combined effects of each component in the composite, i.e., the intentionally introduced nanosheets provide desired electron transport and enhanced light scattering capability, while the nanoparticles retain their large surface area for efficient dye absorption.

Hansen solubility parameters sphere calculations and thermodynamic model fitting of two novel copper complexes supported by bis(imino)pyridine ligands

In this paper, two novel five-coordinated copper(II) metal complexes, [2,6-(ArN = CMe)2C5H3NCuCl2] (Ar = 2-EtC6H4, L1CuCl2; Ar = 4-EtC6H4, L2CuCl2), bearing bulky 2,6-bis[1-(2-ethylphenylimino)ethyl]pyridine ligands L1 (L1 = 2,6-(ArN = CMe)2C5H3N, Ar = 2-EtC6H4), 2,6-bis[1-(4-ethylphenylimino)ethyl]pyridine ligands L2 (L2 = 2,6-(ArN = CMe)2C5H3N, Ar = 4-EtC6H4) have been synthesized and characterized, and the thermodynamic properties of these complexes are reported in a variety of mono-solvents. The copper(II) metal complexes based on bis(imino)pyridine are widely used in catalysis, photoelectric material, biopharmaceuticals and other fields. In this paper, the solubility of L1 and L2 in four solvents, the solubility of L1CuCl2 in four solvents and the solubility of L2CuCl2 in five solvents were studied by static analysis. The solubility of these compounds was investigated in a certain temperature range to provide data to support the selection of optimal solvents for organic reactions, coating and crystallization separations. Hansen solubility parameters (HSPs) were used to explain the dissolution behavior of solutes and were found to be consistent with experimentally measured results. Moreover, the values of HSPs for L1CuCl2 and L2CuCl2 lacking Cu data were simulated by the Hansen Solubility Parameters in Practice (HSPiP) software, which allowed the prediction of solvents with good dissolution behavior. The values of total solubility parameter of Hildebrand (δ) for L1CuCl2 and L2CuCl2 are 24.5 and 23.0, respectively. Besides, solubility properties of L1CuCl2 and L2CuCl2 in two solvent mixtures at different percentages were predicted. In addition, seven thermodynamic models were used to correlate the solubility data. For L1 and L2, Polynomial models fit better with an average absolute relative deviation (ARD) less than 1 %; for L1CuCl2 and L2CuCl2, Polynomial model fits best (ARD < 1 %). In addition, the enthalpy–entropy compensation relationship in the dissolution process was analyzed by calculating the thermodynamic parameters of the substances, and the results showed that the dissolution process of L1 and L2 was an enthalpy-driven heat absorption process.

Novel Bio-based Branched Unsaturated Polyester Resins for High-Temperature Applications

Unsaturated polyester resins, one of the most important thermosets, are invariably produced from oil-based monomers. Their application is limited in areas where high thermal stability is required due to their low Tg. Besides, these resins contain 30–40% hazardous styrene as a reactive solvent. Therefore, developing bio-based solventless unsaturated polyester resin with medium to high thermomechanical properties compared to petrochemical-based counterparts is important. In order to achieve this, a series of branched bio-based unsaturated polyester resins were synthesized using bulk polymerization method in two steps. In the first step, four different intermediates were prepared by reacting glycerol (as a core molecule) with either isosorbide (diol), 1,3-propanediol (diol), 2,5-furandicarboxylic acid (saturated diacid), or adipic acid (saturated diacid). In the second step, the branched intermediate was end capped with methacrylic anhydride to introduce reactive sites for cross-linking on the branch ends. The chemical structure of the resins was characterized by 13C-NMR. FT-IR confirmed the polycondensation reaction in the first step and the end functionalization of the resins with methacrylic anhydride in the second step. The effect of 2,5-furandicarboxylic acid and isosorbide on thermomechanical and thermal properties was investigated using dynamic mechanical analysis, differential scanning calorimetry, and thermo-gravimetric analysis. Results indicated that 2,5-furandicarboxylic acid based resins had superior thermomechanical properties compared to a commercial reference unsaturated polyester resin, making them promising resins for high-temperature composite applications. For example, the resin based on 2,5-furandicarboxylic acid and isosorbide and the resin based on 2,5-furandicarboxylic acid and 1,3-propanediol gave glass transition temperatures of 173 °C and 148 °C, respectively. Although the synthesized 2,5-furandicarboxylic acid based resins had higher viscosity (22.7 Pas) than conventional unsaturated polyester (0.4–0.5 Pas) at room temperature, preheated resins can be used for making high-temperature-tolerance fiber-reinforced composite.

Eutectic Mixtures As Green Solvents for Laccase-Catalyzed Reactions

Eutectic Mixtures As Green Solvents for Laccase-Catalyzed Reactions

Green approach to semisynthesis of apigenin from naringin isolated from very immature pomelo peels

AbstractThe flavanone glycoside naringin, which is abundant in the very immature pomelo peel cultivated in Vietnam, has been demonstrated to have potential use in semisynthesis into other flavonoid compounds, especially apigenin, which exhibits several biological properties and has a greater commercial value. In this study, we carried out an oxidation reaction on flavanone backbone to semisynthesize apigenin with I2 catalyst in some environmentally friendly solvents such as a replacement for the reaction in the pyridine solvent, which is thought to be a non‐green solvent. These solvents which were employed in this investigation included water, DMSO, ethyl acetate, ethanol, ethylene glycol, and vegetable oil. The degree of conversion and the purity of the isolated product were evaluated using the RP‐HPLC‐DAD method, the yield was calculated according to the mass of the obtained crystals, and the synthetic compounds were confirmed by NMR spectra. The results showed that the solvents of DMSO, DMSO:H2O gave the total yield of 93% and the purity of apigenin greater than 95% as compared to 74% and 93%, respectively, with the reaction in pyridine. Our findings revealed that using 10% mol of I2 catalyst was more cost‐effective than conducting the reaction in pyridine, which required an equivalency of substrate and catalyst of 1:1. The solubility of naringin in the solvent combination should be taken into account, though, since this might result in a low yield and influence the degree of conversion.

One-step facile synthesis of polyethylene terephthalate–derived metal–organic framework for liquid-phase adsorption of benzophenone-4

UiO-66 (Universitet i Oslo 66) is a type of metal–organic framework (MOF) comprising zirconium oxoclusters and terephthalic acid that is expected to be applicable as a liquid-phase adsorbent owing to its high thermal and chemical stability and regular pore structure. Recently, MOFs synthesized from polyethylene terephthalate (PET) as a starting material have attracted much attention. However, developing a one-step process for synthesizing PET-derived UiO-66 with high crystallinity and high purity is difficult because the reaction conditions for PET depolymerization and UiO-66 crystallization are different. In this study, we used acetone with hydrochloric acid as a reaction solvent to carry out PET depolymerization and UiO-66 crystallization simultaneously and successfully developed a one-step process for synthesizing PET-derived UiO-66. In experiments, the PET-derived UiO-66 performed comparably to conventional UiO-66 at adsorbing benzophenone-4 from an aqueous solution, which suggests that it is an effective adsorbent. This is the first report of the one-step facile synthesis without the use of special equipment of PET-derived UiO-66 with high crystallinity and high purity.

Synthesis and characterization of the graft copolymer PTFE-g-HEMA using gamma rays for the load and delivery of ciprofloxacin

The aim of this study was to develop a drug delivery copolymer. Hydroxyethyl methacrylate (HEMA) was grafted onto poly(tetrafluoroethylene) films using gamma rays as the initiator agent. The optimal conditions for the grafting procedure were determined through a series of experiments, considering the following factors: reaction time, temperature, HEMA concentration, solvent type, and gamma-ray doses. Grafting was accomplished using the oxidative-pre-irradiation method. The resulting copolymer was subjected to various characterizations, including thermal analysis (TGA and DSC), FTIR-ATR spectroscopy, contact angle measurements, and assessment of physicochemical properties. Additionally, its ability to load and release ciprofloxacin was evaluated.Graphical abstract

Thermal dependence of the hydrated proton and optimal proton transfer in the protonated water hexamer

Water is a key ingredient for life and plays a central role as solvent in many biochemical reactions. However, the intrinsically quantum nature of the hydrogen nucleus, revealing itself in a large variety of physical manifestations, including proton transfer, gives rise to unexpected phenomena whose description is still elusive. Here we study, by a combination of state-of-the-art quantum Monte Carlo methods and path-integral molecular dynamics, the structure and hydrogen-bond dynamics of the protonated water hexamer, the fundamental unit for the hydrated proton. We report a remarkably low thermal expansion of the hydrogen bond from zero temperature up to 300 K, owing to the presence of short-Zundel configurations, characterised by proton delocalisation and favoured by the synergy of nuclear quantum effects and thermal activation. The hydrogen bond strength progressively weakens above 300 K, when localised Eigen-like configurations become relevant. Our analysis, supported by the instanton statistics of shuttling protons, reveals that the near-room-temperature range from 250 K to 300 K is optimal for proton transfer in the protonated water hexamer.

State-of-the-art for the development of Cu-based heterogeneous catalysts for efficient utilization of furfural to value chemicals via liquid-phase and gas-phase reactions

ABSTRACT In the present review, we aim to provide important insights into copper-based heterogeneous catalytic systems and discuss the conversion of furfural (FF) through hydrogenation. Each discussed catalyst and the support used for the catalytic reactions play a vital role in the reaction mechanism along with different factors enhancing the catalytic activity. Also, the importance of Cu-based materials along with support, the importance of solvent in the liquid-phase reaction, and the importance of pre-reduction of catalysts are explained in detail. In addition, the superior activity of the catalyst and a few reports from the last decade for Cu-based catalytic systems have been summarized along with the tabulation of different synthesis procedures, mechanistic study, and detailed descriptions with tables and figures. Finally, the conclusions with future aspects for the development of the catalytic hydrogenation process via Cu-based catalytic systems are overviewed.

Photocatalytic Degradation of Tetracycline Hydrochloride by Mn/g-C3N4/BiPO4 and Ti/g-C3N4/BiPO4 Composites: Reactivity and Mechanism

The environmental pollution caused by antibiotics is becoming more serious. In this study, the Mn/BiPO4/g-C3N4 composite (Mn-BPC) and the Ti/g-C3N4/BiPO4 composite (Ti-BPC) were prepared by hydrothermal reaction method and solvent method, respectively, and applied to the degradation of tetracycline (TC) in an aqueous environment. The XRD and HRTEM results showed that these materials had the crystalline rod-like structure of BiPO4 and abundant carbon, nitrogen and carbon–oxygen surface functional groups. The degradation of TC by Ti-BPC and Mn-BPC were nearly 92% and 79%, respectively. The degradation processes of TC were well consistent with the pseudo-second-order kinetics model and R2 values were closer to 1. The trapping experiment showed that electron holes (h+) were the main reactive species for the degradation of tetracycline, OH· and O2− also have certain effects. Also, the possible photocatalytic degradation mechanism of Ti-BPC and Mn-BPC composites was thereby proposed. TC was firstly adsorbed on the surface of catalysts, and subsequently degraded by reactive species such as h+, OH· and O2− generated under visible light excitation. This study shows that the Ti-BPC and Mn-BPC photocatalysts have great potential in antibiotic degradation and can provide new ideas for antibiotic removal in aqueous environments.

Light-induced reduction of aryl ketones and aldehydes via Meerwein-Ponndorf-Verley-type reaction with isopropanol under Mild reaction conditions

In the realm of green chemistry, the quest for increasingly eco-friendly and economically viable methods for the transformation of aldehydes and ketones into alcohols assumes critical importance. In the present study, we introduce an innovative approach that enables the direct and light-induced reduction of aldehydes and ketones to alcohols. This method harnesses isopropanol, serving the dual role of both the reaction solvent and reducing agent, in conjunction with t-BuOK. This operationally straightforward, light-promoted strategy follows the Meerwein-Ponndorf-Verley reduction pathway and demonstrates remarkable efficacy in the synthesis of diverse benzylic alcohol derivatives.

Visible-Light-Initiated Air-Oxygenation of Alkylarenes to Carbonyls Mediated by Carbon Tetrabromide in Water.

Synthesizing benzyl skeleton derivatives via direct oxidation of functionalized benzylic C-H bonds has received extensive research attention. Herein, a method was developed to prepare carbonyl compounds via photoinduced aerobic oxidation of ubiquitous benzylic C-H bonds mediated by bromine radicals and tribromomethane radicals. This method employed commercially available CBr4 as a hydrogen atom transfer reagent precursor, air as an oxidant, water as a reaction solvent, and tetrabutylammonium perchlorate (TBAPC) as an additive under mild conditions. A series of substrates bearing different functional groups was converted to aromatic carbonyls in moderate to good yields. Moreover, a low environmental factor (E-factor value=0.45) showed that the proposed method is ecofriendly and environmentally sustainable.