1H NMR Research Articles

Ferrocenyl Dithiophosphonate Ag(I) Complexes: Synthesis, Structures, Luminescence, and Electrocatalytic Water Splitting Tuned by Nuclearity and Ligands.

The heterometallic [Ag(I)/Fe(II)] molecular electrocatalysts for hydrogen production were introduced here to recognize the mutual role of metallic nuclearity and ligand engineering. A series of ferrocenyl dithiophosphonate stabilized mononuclear [Ag(PPh3)2{S2PFc(OR)}] {where R=Me (1), Et (2), nPr (3), iPr (4), iAmyl (5); Fc=Fe (ɳ5-C5H4) (ɳ5-C5H5)} and dinuclear [Ag(PPh3){S2PFc(OR}]2 {where R=Et (2 a), and nPr (3 a)} complexes were synthesized and characterized by SCXRD, NMR (31P and 1H), ESI-MS, UV-Vis, and FT-IR spectroscopy. The comparative electrocatalytic HER behavior of 1-5 and 2 a-3 a showed effective current density of 1 mA/cm2 with overpotentials ranging from 772 to 991 mV, demonstrating the influence of extended and branched carbon chains in dithiophosphonates and metallic (mono-/di-) nuclearity, which correlates with documented tetra-nuclear [Ag4(S2PFc(OnPr)4], 6. DFT study suggests the coordinated (μ1-S) site of ligands is the reactivity center and the adsorption energy of intermediate [H*-SM] varies with the engineering of ligand and nuclearity. A catalytic mechanism using mononuclear (1) and di-nuclear (2 a) was proposed with the assistance of DFT. Each complex, being the first example of Ag(I) dithiophosphonates, exhibits intense photoluminescence with high quantum yields ranging from 33 % to 67 %. These results link the lower nuclearity structures to their physical and catalytic properties.

Naked eye detection of anions: Dihydrazone receptor-based visual sensing

In this study, we designed and synthesized a novel colorimetric sensor for fluoride ions by integrating a thienodicarbohydrazide framework with salicylaldehyde, resulting in a unique bis-hydrazone-phenol receptor. This sensor exhibited exceptional selectivity for fluoride and acetate ions in nonaqueous environments, with detection visible to the naked eye. Upon interaction with fluoride ions, the receptor underwent a significant red shift in its UV–Visible absorption spectrum, moving from an absorption maximum at 332 nm–380 nm, signalling the recognition event. Acetate ions induced a similar shift. The binding interactions were thoroughly investigated, with a Jobs plot revealing a 1:1 receptor-anion complex formation with fluoride ions and a 1:2 complex with acetate ions. Further validation came from 1H NMR titration, which confirmed the presence of hydrogen bonding interactions between the receptor and the ions. The receptor demonstrated remarkable binding constants of 5.2 × 10⁴ M−2 for acetate and 1.6 × 10⁴ M−1 for fluoride ions, highlighting its strong and selective affinity. Fluorescence titrations further confirmed the receptor's potential as a chemo sensor, showing distinct emission changes in the presence of fluoride and acetate ions. This study not only underscores the receptor's capability for visual detection of fluoride ions in non-aqueous systems but also paves the way for its application in diverse analytical and environmental settings.

Soil Analysis by Mobile Multinuclear NMR: Quantification of Phosphorus, Aluminum, and Sodium.

Soil analyses are essential to ensure economically and environmentally sustainable crop production while maintaining the soil fertile for future use. Unfortunately, common soil analyses may be highly demanding in terms of time, chemicals, and costs. This applies, in particular, when total quantities of elements are desired. As an easy and fast alternative without consumption of chemicals, we here present mobile 31P, 27Al, 23Na, and 1H NMR for quantification of phosphorus, aluminum, and sodium contents in soil. This enables accurate on-site analysis and is suitable for direct measurement on fresh, undried soil samples since the water content is quantified as well. For demonstration, 40 various Danish agricultural soil samples were analyzed using a mobile NMR sensor, and the results were compared with external laboratory analyses for P, Al, and Na. The laboratory analyses were conducted with ICP-OES after four-acid digestion, which additionally were compared with aqua regia digestion, showing inadequacies in the performance of the latter. Good agreement between NMR and laboratory analyses (correlation coefficients 0.91 for P, 0.98 for Al, and 0.90 for Na, in the concentration ranges 250-1200 ppm P, 1.4-5% Al, and 0.3-1% Na) were obtained with high accuracy using NMR measuring times of 20 min to 1 h for P, 4-12 min for Al, and 6-20 min for Na. Additionally, the NMR measurements provide information on the amount of P associated with paramagnetic centers (e.g., Fe3+). Good correlations were also observed to other parameters such as the clay content, which is predictable from the intensity of the more fast-relaxing of three 27Al NMR components.

Design of experiments optimization of N,N,N-trimethyl chitosan synthesis using N,N-diisopropylethylamine base

This study presents a novel synthesis method of N,N,N-trimethyl chitosan (TMC) by using a non-nucleophilic base and optimizing the solvent system for enhanced scalability, while addressing critical factors such as viscosity management and stirring efficiency. The study objectives also included achieving high N,N,N-trimethylation without O-methylation while minimizing reagent use. Eight bases, three solvent systems, and varying levels of dilution were explored to mitigate viscosity challenges and gas evolution. 1H NMR spectroscopy was used to characterize the TMC products. The integral values of the peaks at 3.3, 3.0, and 2.8 ppm, corresponding to trimethyl, dimethyl, and monomethyl groups, were used to quantify the methylation degrees. The most promising initial results were obtained with N,N-diisopropylethylamine (DIPEA) base, and DMF as solvent. Using 6 eq methyl iodide (MeI) relative to chitosan and DIPEA as base, up to 68 % DTM was achieved. Applying Design of Experiments (DoE), the method was further optimized under diluted conditions, crucial for industrial scalability and viscosity control. Results from a full factorial design (32) revealed that diluted medium effectively prevented viscosity concerns, achieving a notably low viscosity of 5.9 cP in the reaction mixture, a 16-fold decrease in viscosity, compared to initial experiments. It was also established that both the MeI reagent and the base addition are significant factors for the DTM response, with both factors showing quadratic effects. The DoE model demonstrated high significance (R = 0.97), high precision for future prediction (Q2 = 0.87), good model validity (0.84) and excellent reproducibility (0.96). The results mark a notable advancement in TMC synthesis, offering an efficient and practical method with significant implications for industrial applications.

Non-targeted metabolomics and pseudo-targeted lipidomics combined with gut microbes reveal the protective effects of Causonis japonica (Thunb.) Raf. in ulcerative colitis mice.

Ulcerative colitis (UC) is an inflammatory bowel disease characterized by recurrent inflammatory tissue damage to the intestinal mucosa and forming intestinal epithelial ulcers. It is one of the most intractable diseases in the world. To date, the mechanism is unclear. Causonis japonica (Thunb.) Raf. (Wu Lianmei in Chinese; WLM), a traditional Chinese medicine, which has a long history as an anti-inflammatory, but its effect on UC was unconfirmed yet. Therefore, we established a dextran sodium sulfate (DSS)-induced UC mice model and evaluated the therapeutic effect of WLM extract. The results indicated that WLM inhibits DSS-induced inflammatory response in colitis in vivo, decrease DSS-induced clinical manifestations, reverses colon length shortening, and reduces tissue damage. The results of ELISA kits suggested that WLM could reverse the levels of DSS-induced inflammatory factors. To explore the mechanism of WLM in treating DSS-induced UC, 1H NMR and UHPLC-Q/Orbitrap MS were used to perform non-targeted metabolomics analysis; 21 differential metabolites in colon tissues were closely related to UC. Meanwhile, the pseudo-targeted lipidomics based on UHPLC-Q/Trap MS was used to analyze lipid metabolism disorders, and 60 differential lipid compounds were screened. These differential compounds were mainly involved in glycerophospholipid, arachidonic acid, glycerolipid, citric acid, tyrosine, and ether lipid metabolisms. The analysis of gut microbial showed that WLM may improve the symptoms of UC mice by reducing the abundance of Helicobacter and Streptococcus and increasing the abundance of Limosilactobacillus and Akkermansia. Moreover, the real-time qPCR results showed that WLM extract could decrease the mRNA levels of inflammatory factors and may be associated with protecting the integrity of intestinal mucosal barrier by destroying in vivo metabolic pathways, especially by regulating energy and lipid metabolisms and reducing inflammatory reactions. It provides a beneficial reference for studying WLM to elucidate the therapeutic mechanism of UC.

Preparation and Properties Improvement of Decynediol-Ethoxylate-Modified Trisiloxane Surfactant.

Silicone surfactants are increasingly used in the industrial field due to their advantages such as low surface energy, stable performance, and good biocompatibility. However, many polyether-modified silicone surfactants' foam stability and easy hydrolysis in non-neutral aqueous systems limit their application in many fields. In this article, the decynediol-ethoxylate chain segment was grafted onto heptamethyltrisiloxane to synthesize a modified trisiloxane surfactant (G2). FT-IR and 1H NMR characterized its structure. Its surface activity, aggregation behavior, and wetting and spreading properties in water were studied by using instruments such as a surface tension meter, transmission electron microscope (TEM), dynamic light scattering (DLS), and contact angle tester. G2 can reduce the surface tension of water to 19.24 mN/m at a lower CMC (40.44 mg/L), and the foaming properties and hydrolysis stability of decynediol-ethoxylate-modified trisiloxane (G2) in water are significantly improved compared with allyl-polyoxyethylene-ether-modified trisiloxane (X5).

Purification Processes for Generating Cationic Lignin-Acrylamide Polymers.

Purification is an essential step in many polymerization processes for fabricating highly pure polymers. This study considered various purification methods for purifying the product of lignin, acrylamide (AM), and diallyl dimethylammonium chloride (DADMAC) copolymerization reactions at a laboratory scale. The charge density, yield, molecular weight, and solubility analyses confirmed that ethanol extraction and membrane filtration were the most effective processes for producing lignin-p(AM)-p(DADMAC). The 1H NMR analysis revealed that the membrane dialysis effectively removed unreacted AM and DADMAC monomers from the reaction medium. The produced samples of the ethanol-extraction and dialysis processes had higher solubility and yield compared to the product of the acidification process. Thermogravimetric studies confirmed that the ethanol-extracted and dialyzed samples had a degradation temperature (220 °C) higher than that of the acidified samples (160 °C). The rheological studies confirmed that the viscosities of the polymer solutions were influenced more by the solubility than by the molecular weight of the generated polymers within the molecular weight range examined in this study. The flocculation studies confirmed that the ethanol-extracted and dialyzed polymers were more effective flocculants than the acidified samples for the particles of a kaolinite suspension. Based on the above results, membrane filtration with a larger pore size could be an environmentally friendly method for effectively purifying lignin-p(AM)-p(DADMAC).

Enhancing protein extraction from Pleurotus ostreatus using synergistic pH-shifting and ultrasonic technology: Optimization via RSM and 1H NMR-based metabolomic profiling

This study explores the impact of ultrasound and pH-shifting on protein extraction from P. ostreatus, employing 1H NMR techniques to monitor metabolites and elucidate the extraction mechanism. The NMR-based metabolic analysis demonstrated that extended sonication time significantly boosted amino acid release. To optimize conditions for maximizing protein yield, response surface methodology was performed. This research aims to enhance protein extraction from P. ostreatus by analyzing the interplay between ultrasound treatment and pH-shifting. The results indicate that the synergistic use of pH-shifting and ultrasound-assisted extraction (UAE) significantly improves protein yield. The amino acid profile of the protein concentrates revealed a high content of essential amino acids, with tryptophan identified as the limiting amino acid. Additionally, the combined extraction method enhanced the emulsifying properties and foaming stability of the protein concentrates. Thus, combining pH-shifting and UAE is a promising technique for extracting high-quality protein from P. ostreatus, enhancing functional properties and efficiency.

Gradient Functionalization of Poly(lactic acid)-Based Materials with Polylysine for Spatially Controlled Cell Adhesion.

The development of biomaterials with gradient surface modification capable of spatially controlled cell adhesion and migration is of great importance for tissue engineering and regeneration. In this study, we proposed a method for the covalent modification of PLA-based materials with a cationic polypeptide (polylysine, PLys) via a thiol-ene click reaction carried out under a light gradient. With this aim, PLA-based films were fabricated and modified with 2-aminoethyl methacrylate (AEMA) as a double bond source. The latter was introduced by reacting pre-formed and activated surface carboxyl groups with the amino group of AEMA. The success of the modification was confirmed by 1H NMR, Raman and X-ray photoelectron spectroscopy data. A further photoinduced thiol-ene click reaction in the presence of a photosensitive initiator as a radical source was further optimized using cysteine. For grafting of PLys via the thiol-ene click reaction, PLys with a terminal thiol group was synthesized by ring-opening polymerization using Cys(Acm) as an amine initiator. Deprotection of the polypeptide resulted in the formation of free thiol groups of Cys-PLys. Successful gradient grafting of Cys-PLys was evidenced by covalent staining with the fluorescent dye Cy3-NHS. In addition, PLys gradient-dependent adhesion and migration of HEK 293 cells on PLys-PLA-based surfaces was confirmed.

Preparation and performance evaluation of a low‐damage fracturing fluid for unconventional reservoirs

AbstractThe characteristics of tight matrix, underdeveloped natural fractures, small pore throat radius, poor pore connectivity, and abundant clay minerals result in a high potential for damage to the tight sandstone reservoirs of the Shaximiao Formation in the Qiulin Block in the Sichuan Basin. In order to reduce the retention damage caused by fracturing fluid to the tight sandstone reservoir, a low damage fracturing fluid system applicable to the target reservoir is developed in this work, and the indoor performance meets the requirements of on‐site fracturing operation. A low‐damage, heat‐resistant, shear‐stable amphiphilic polyacrylamide (PAAD) was prepared by free radical polymerization in aqueous solution using acrylamide, acrylic acid, and methacryloyloyloxyethyl dimethyloctadecyl ammonium bromide (DM18) as the monomers. The amphoteric polyacrylamide was characterized by Fourier infrared spectroscopy, nuclear magnetic resonance spectroscopy (1H NMR), light scattering molecular weight determination, and thermogravimetric analysis. Fracturing fluids were formulated with the amphiphilic hydrophobic associative polymer PAAD as a drag‐reducing agent, the fluorine‐containing and nonionic complex surfactant FD1 as a clean‐up additive, CT10‐4B as a bactericide and CT1‐12 as an emulsion breaker. The fracturing fluid formulation was preferred, and the performance of the fracturing fluid was evaluated in terms of temperature resistance and shear resistance, drag reduction, anti‐expansion, and core damage. The fracturing fluid showed good temperature and shear resistance, with a viscosity retention of 58.4% at 120°C and 170 s−1 shear for 1 h. At a loading of 0.1%, the drag reduction rate reaches 72.3%, the anti‐expansion rate of the gel‐breaking fluid is 86.04%, and the damage rate to the tight sandstone core is 16.25%. The results show that the fracturing fluid has good heat resistance and shear stability, as well as low damage and good resistance reduction and anti‐expansion properties. This work can provide new strategies for designing polymeric fracturing fluids with low damage, good heat resistance and shear stability.

Synthesis, thermal and spectroscopic analysis, antimicrobial activities and molecular modeling of zinc(II) metal complex of benzoyl glycine

To analyze ligand characteristics and use, a benzamide-derived ligand(benzoyl glycine) was synthesized and characterized before complexing it with zinc(II) ions. The ligand was formed from benzamide and glycine, obtained upon purification and precipitation. FTIR and 1H NMR were used to characterize the ligand. Furthermore, thermogravimetric analysis (TGA) was used to study the thermal behavior of the ligand and its Zn(II) complex, revealing important thermodynamic characteristics. The zinc complex was subjected to X-ray powder diffraction experiments, which yielded structural insights. Density Functional Theory (DFT) calculations were used in molecular modeling to clarify structure and characteristics of the molecules. Moreover, anti-microbial tests were used to assess biological activity against E. Coli and A. Niger. This thorough investigation lays the foundation for future research in this area by offering insightful information about the synthesis, characterization, and possible uses of the ligand and its Zn(II) metal complexes.

Synthesis, characterization, molecular modeling, and antimicrobial study of copper(II) 2-chlorophenylacetohydroxamate

A copper(II) 2-chlorophenylacetohydroxamate complex has been synthesized using copper(II) chloride and potassium 2-chlorophenylacetohydroxamate in 1:2 molar ratio in methanol and characterized using CHN analysis, IR, 1H NMR, 13C NMR spectroscopy, and mass spectrometry. The hydroxamate ligand binds to metal via oxygen of carbonyl group and hydroxamic group (O, O bonding), and a distorted-square planar geometry has tentatively been proposed. The interactions between Staphylococcus aureus (bacterial receptor) ligand and complex, their inhibition constant, and binding energy values have been computed. The in vitro antimicrobial activity study against pathogenic gram –ve bacteria viz. Salmonella typhi and Escherichia coli; gram + ve S. aureus and Bacillus cereus by MIC method have revealed a significant antimicrobial potential.

Synthesis and biological activity of substituted 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxamides

A four-component solvent-free reaction of acetoacetic acid amide with dimedone, aromatic aldehydes and ammonium acetate leads to new substituted 5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxamides. The structures of the products were proved using IR, 1H and 13C NMR spectroscopy, mass spectrometry and X-ray diffraction analysis. The synthesized compounds were tested for antimicrobial and antinociceptive activities.

Stabilization of the Compressed Planar Benzene Dianion in Inverse-Sandwich Rare Earth Metal Complexes.

For the first time, the capture of a planar antiaromatic benzene dianion in between two trivalent rare earth (RE) metal cations, each stabilized by two guanidinate ligands, is reported. The synthesized inverse-sandwich complexes [{(Me3Si)2NC(NiPr)2}2RE]2(µ-ƞ6:ƞ6-C6H6), (RE = Y (1), Dy (2), and Er (3)) feature a remarkably planar benzene dianion, previously not encountered for any metal ion prone to low or absent covalency. The -2 charge localization at the benzene ligand was deduced from the results obtained by single-crystal X-ray diffraction analyses, spectroscopy, magnetometry, and Density Functional Theory (DFT) calculations. In the 1H NMR spectrum of the diamagnetic Y complex 1, the equivalent proton resonance of the bridging benzene dianion ligand is drastically shifted to higher field in comparison to free benzene. This and the calculated highly positive Nucleus-Independent Chemical Shift (NICS) values are attributed to the antiaromatic character of the benzene dianion ligand. The crucial role of the ancillary guanidinate ligand scaffold in stabilizing the planar benzene dianion conformation was also elucidated by DFT calculations. Remarkably, the planarity of the benzene dianion originates from the stabilization of the π-type orbitals of the d-manifold and compression through its strong electrostatic interaction with the two REIII sites.

Synthesis and structure of 4-(het)aryl-6-methyl-2-cyanoimino-N,N-diethyl-1,2,3,4-tetrahydropyrimidine-5-carboxamides

A series of previously unknown 4-(het)aryl-6-methyl-2-cyanoimino-N,N-diethyl-1,2,3,4-tetrahydropyrimidine-5-carboxamides was synthesized by the reaction of N,N-diethyl-3-oxobutanamide with (het)arylaldehydes and N-cyanoguanidine. The structure of the obtained compounds was established by IR, 1H NMR spectroscopy and single crystal X-ray diffraction analysis.

Stabilization of the Compressed Planar Benzene Dianion in Inverse‐Sandwich Rare Earth Metal Complexes

For the first time, the capture of a planar antiaromatic benzene dianion in between two trivalent rare earth (RE) metal cations, each stabilized by two guanidinate ligands, is reported. The synthesized inverse‐sandwich complexes [{(Me3Si)2NC(NiPr)2}2RE]2(µ–ƞ6:ƞ6–C6H6), (RE = Y (1), Dy (2), and Er (3)) feature a remarkably planar benzene dianion, previously not encountered for any metal ion prone to low or absent covalency. The ‐2 charge localization at the benzene ligand was deduced from the results obtained by single‐crystal X‐ray diffraction analyses, spectroscopy, magnetometry, and Density Functional Theory (DFT) calculations. In the 1H NMR spectrum of the diamagnetic Y complex 1, the equivalent proton resonance of the bridging benzene dianion ligand is drastically shifted to higher field in comparison to free benzene. This and the calculated highly positive Nucleus‐Independent Chemical Shift (NICS) values are attributed to the antiaromatic character of the benzene dianion ligand. The crucial role of the ancillary guanidinate ligand scaffold in stabilizing the planar benzene dianion conformation was also elucidated by DFT calculations. Remarkably, the planarity of the benzene dianion originates from the stabilization of the π‐type orbitals of the d‐manifold and compression through its strong electrostatic interaction with the two REIII sites.

Synthesis of 1-aminoalkyl-5,6-diaryl-2-oxopyrrolo[3,4-<i>c</i>]pyrazoles

The reaction of substituted 1-aminoalkyl-3-hydroxy-3-pyrrolin-2-ones with hydrazine hydrate in boiling glacial acetic acid leads to the formation of 1-aminoalkyl-5,6-diaryl-2-oxopyrrolo[3,4-c]pyrazoles. The structure of the obtained compounds was confirmed by IR, 13C NMR and 1H NMR spectroscopy methods.

Facile synthesis of polyester-polyether block copolyols for the sustainable high-performance polyurethane reactive hot melt adhesives

The presence of polyols with both polyester and polyether structures in polyurethane enhances bonding strength and facilitates easy curing. In this study, polyester-polyether block polyols with varying molecular weights (2500–3500) were synthesized through ring-opening polymerization (ROP) using l-lactide (LA) and ε-Caprolactone (CL). The chemical structure of the polyols was characterized using 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared (FTIR), and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were employed to examine the crystalline morphology of the polyols. Subsequently, the synthesized polyols were combined with 4,4′-diphenylmethane diisocyanate (MDI) and other additives to prepare polyurethane reactive hot melt adhesives. It was observed that, in PCL-based polyurethane reactive hot melt adhesives, increasing the molecular weight of the polyols resulted in improved crystalline morphology, increased lap shear strength and tensile strength, and enhanced thermal stability. On the other hand, PLA-based polyurethane reactive hot melt adhesives exhibited low bonding strength and lacked practical application value due to the poor toughness of PLA. Interestingly, the bonding strength and tensile strength of PLA-based polyurethane reactive hot melt adhesives improved when physically blended with PCL-based polyurethane reactive hot melt adhesives. These polyols offer a novel approach for utilizing LA and CL in adhesive applications.

Preparation of Allyl-Containing PDMS Telehelics by the Anionic Ring-Opening Polymerization

The synthesis of allyl-containing PDMS telechelics from octamethylcyclotetrasiloxane and 1,3-diallyl-1,1,3,3-tetramethyldisiloxane as a stopper by the anionic ring-opening of a siloxane ring is presented. A series of the polymers with the molecular weights from 1000 to 12000 were obtained and characterized by gel permeation chromatography and 1H NMR spectroscopy. The molecular weights of the resulting polymers correspond to the given ones.

A tale of two old drugs tetracycline and salicylic acid with new perspectives—Coordination chemistry of their Co(II) and Ni(II) complexes, redox activity of Cu(II) complex, and molecular interactions

Extensive use of the broad-spectrum tetracycline antibiotics (TCs) has resulted their wide spread in the environment and drive new microecological balances, including the infamous antibiotic resistance. TCs require metal ions for their antibiotic activity and resistance via interactions with ribosome and tetracycline repressor TetR, respectively, at specific metal-binding sites. Moreover, the Lewis-acidic metal center(s) in metallo-TCs can interact with Lewis-basic moieties of many bioactive secondary metabolites, which in turn may alter their associated chemical equilibria and biological activities. Thus, it is ultimately important to reveal detailed coordination chemistry of metallo-TC complexes. Herein, we report (a) conclusive specific Co2+, Ni2+, and Cu2+-binding of TC revealed by paramagnetic 1H NMR, showing different conformations of the coordination and different metal-binding sites in solution and solid state, (b) significant metal-mediated activity of Cu-TC toward catechol oxidation with different mechanisms by air and H2O2 (i.e., mono- and di-nuclear pathways, respectively), (c) interactions of metallo-TCs with bioactive salicylic acid and its precursor benzoic acid, and (d) noticeable change of TC antibiotic activity by metal and salicylic acid. The results imply that TCs may play broad and versatile roles in maintaining certain equilibria in microecological environments in addition to their well-established antibiotic activity. We hope the results may foster further exploration of previously unknown metal-mediated activities of metallo-TC complexes and other metalloantibiotics.