Search Results (114)

Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η⁶-p-cymene)(L)Cl][PF₆] (1–8) and [Ru(η⁶-p-cymene)(L)Cl][Ru(η⁶-p-cymene)Cl₃] (9–11) were synthesized and fully characterized. These were prepared from the reaction of pyridine–quinoline and biquinoline-based ligands (L) with [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂, in 1:2 and 1:1, metal (M) to ligand (L) molar ratios. Characterization includes a combination of spectroscopic methods (FT-IR, UV-Vis, multi nuclear NMR), elemental analysis and single-crystal X-ray crystallography. The pyridine–quinoline organic entities encountered, were prepared in high yield either via the thermal decarboxylation of the carboxylic acid congeners, namely 2,2′-pyridyl-quinoline-4-carboxylic acid (pqca), 8-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8-Mepqca), 6′-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (6′-Mepqca) and 8,6′-dimethyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8,6′-Me₂pqca), affording the desired ligands pq, 8-Mepq, 6′-Mepq and 8,6′-Me₂pq, or by the classical Friedländer condensation, to yield 4,6′-dimethyl-2,2′-pyridyl-quinoline (4,6′-Me₂pq) and 4-methyl-2,2′-pyridyl-quinoline (4-Mepq), respectively. The solid-state structures of complexes 1–4, 6, 8 and 9 were determined showing a distorted octahedral coordination geometry. The unit cell of 3 contains two independent molecules (Ru-3), (Ru′-3) in a 1:1 ratio, due to a slight rotation of the arene ring. All complexes catalyze the transfer hydrogenation of acetophenone, using 2-propanol as a hydrogen donor in the presence of KOiPr. Among them, complexes 1 and 5 bearing methyl groups at the 8 and 4 position of the quinoline moiety, convert acetophenone to 1-phenylethanol quantitatively, within approximately 10 min with final TOFs of 1600 h⁻¹. The catalytic performance of complexes 1–11, towards the transfer hydrogenation of p-substituted acetophenone derivatives and benzophenone, ranges from moderate to excellent. An inner-sphere mechanism has been suggested based on the detection of ruthenium(II) hydride species. Full article

Bis- and trisphosphines incorporating methylene and aryl spacers readily adsorb on the surface of porous activated carbon (AC). The adsorption can be performed in the absence of solvents, even when the phosphines have high melting points, or from solutions. The diverse phosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp), Ph₂P(p-C₆H₄)PPh₂ (dppbz), and (Ph₂PCH₂)₃CCH₃ (tdme) were adsorbed in submonolayers on AC. The adsorbed phosphines were studied by ³¹P MAS (magic angle spinning) NMR spectroscopy, and their mobilities on the surface were confirmed by determining the ³¹P T₁ relaxation times. All phosphine groups of each bis- and trisphosphine molecule are in contact with the surface, and the molecules exhibit translational mobility as one unit. All phosphines used here are air-stable. Once a submonolayer is created on the AC surface, oxygen from the air is co-adsorbed and transforms all phosphines quantitatively into phosphine oxides at room temperature. The oxidation proceeds in a consecutive manner with the oxidation of one phosphine group after another until the fully oxidized species are formed. Studies of the kinetics are based on integrating the signals in the solution ³¹P NMR spectra. High temperatures and low surface coverages increase the speed of the oxidation, while light and acid have no impact. The oxidation is fast and complete within one hour for 10% surface coverage at room temperature. In order to study the mechanism and slow down the oxidation, a higher surface coverage of 40% was applied. No unwanted P(V) side products or water adducts were observed. The clean phosphine oxides could be recovered in high yields by washing them off of the AC surface. The oxidation is based on radical activation of O₂ on the AC surface due to delocalized electrons on the AC surface. This is corroborated by the result that AIBN-derived radicals enable the air oxidation of PPh₃ in solution at 65 °C. When the air-stable complex (CO)₂Ni(PPh₃)₂ is applied to the AC surface and exposed to the air, OPPh₃ forms quantitatively. The new surface-assisted air oxidation of phosphines adsorbed on AC renders expensive and hazardous oxidizers obsolete and opens a synthetic pathway to the selective mono-oxidation of bis- and trisphosphines. Full article

Background: During aging, protein nutrition has a bidirectional role in regulating healthy lifespan by modulating body metabolism and neurological function. However, the current “low-high” hypothesis on the dynamics of protein requirements is mainly based on male animal models, and its applicability to female physiology (e.g., estrogen fluctuations) is unclear. The present study aims to fill the gap in the study of protein demand dynamics in female naturally aging mice and to investigate the effects of different protein levels on the health status of female C57BL/6J mice at different stages of aging. Methods: In this study, four dietary interventions (high protein, HP; low protein, LP; model test, MT; and control, C) were evaluated by constructing a C57BL/6J female mouse model at three ages, 9 M (9 months), 16 M (16 months), and 20 M (20 months), which are approximately equivalent to 34, 65, and 78 years of age in humans, respectively, to determine the effects on naturally aging mice. The effects of the interventions were quantitatively described by behavioral, neuropathological, oxidative, and inflammatory indices and NMR metabolomics using Principal Component Analysis to construct a comprehensive quantitative scoring method. Results: The comprehensive quantitative scores Fsum was highest in the HP group, lowest in the LP group, and in between in the MT group. The HP intervention showed the most significant improvement in the aged group (20 M) mice, with a 35.2% reduction in avoidance latency (p < 0.01) and a 32.9% increase in pyramidal cell density in the hippocampal CA1 region (p < 0.05), while the LP intervention led to a cognitive decline in the mice, with an avoidance latency that was prolonged by 15.2% (p < 0.05). Metabolomics analysis revealed that mouse samples of all ages showed age-dependent metabolic re-adaptation: the 9 M group may reflect gut microbial metabolism rather than direct host TCA cycle activity, suggesting an indirect association with energy metabolism; an enhanced degradation of branched-chain amino acids (BCAAs) was seen in the middle-aged group (16 M); and amino acid biosynthesis was predominant in the old group (20 M). Conclusions: Female mice have sustained neuromotor benefits to high-protein diets at different aging stages, and the dynamics of their protein requirements differ significantly from those of males. The study reveals the critical role of gender factors in protein nutritional strategies and provides an experimental basis for precise protein supplementation in older women. Full article

The spiro compound, 5,5′-dimethoxy-1,3-bis(3-(trifluoromethyl)phenyl)-3,3a-dihydro-1H-spiro[cyclopenta[a]indene-2,2′-indene]-1′,8(3′H,8aH)-dione (4), was synthesized and identified by NMR spectroscopy, mass spectrometry, and X-ray crystallography. Compound 4, C₃₆H₂₆F₆O₄, was crystallized in the triclinic space group P-1with the cell parameters a = 8.8669(5) Å, b = 10.5298(8) Å, c = 17.0135(11) Å, α = 91.396(2)°, β = 90.490(2)°, γ = 109.235°, V = 1499.14(17) ų, Z = 2. In an asymmetric unit, two molecules are packed by short contacts to form an inversion dimer. The molecules are linked into chains along the a- and b-axis directions by additional short contacts in the crystal. Compound 4 was synthesized by the dimerization of (E)-5-methoxy-2-(3-(trifluoromethyl)benzylidene)-2,3-dihydro-1H-inden-1-one (3). (E)-5-Methoxy-2-(3-methoxybenzylidene)-2,3-dihydro-1H-inden-1-one (5), one of the analogs of compound 3, was compared with compound 4 based on in vitro experiments, DFT calculations, and an in silico docking study. The HOMO/LUMO energy difference and binding energy difference between the two compounds are consistent with the results obtained from an in vitro assay where 4 showed a better effect than 5. To evaluate the biological activity of 4, we examined its inhibitory effects on Early Growth Respone-1 (EGR-1)-regulated gene expression in HaCaT keratinocytes. Treatment of cells with 4 reduced interleukin-4 (IL-4)-induced thymic stromal lymphopoietin (TSLP) mRNA levels, as revealed by reverse transcription-polymerase chain reaction and quantitative real-time PCR. Furthermore, the electrophoretic mobility shift assay demonstrated that 4 inhibited IL-4-induced DNA binding of EGR-1 to the promoter region of the TSLP gene. Full article

Enzymatic modification of Kraft lignin under alkaline conditions was investigated using bilirubin oxidase (BOD) in borate buffer (pH 10). Control solubilization without enzyme addition revealed a notable increase in molar mass (up to 1.7-fold) and potential borate complexation with lignin hydroxyl groups, as evidenced by thermogravimetric and ¹¹B NMR analyses. BOD treatments induced substantial polymerization, with molar mass increases of up to 4-fold for insoluble fractions after 24 h, while soluble fractions exhibited progressive increases over 5 days. Quantitative ³¹P NMR showed reductions in aliphatic and phenolic hydroxyl groups by 20%, suggesting oxidative coupling reactions, particularly through 4-O-5′ and 5-5′ linkages. Solid-state ¹³C NMR confirmed structural changes associated with polymerization. Dynamic light scattering (DLS) indicated the presence of colloidal aggregates, potentially explaining challenges in HSQC NMR signal acquisition. These findings highlight the efficacy of bilirubin oxidase in catalyzing lignin polymerization and underscore the structural impact of borate–lignin interactions in alkaline media, paving the way for advanced lignin valorization strategies. Full article

With the development of the chemical industry, the threat of mercury pollution to human health is increasing. Therefore, it is necessary to develop a low-cost, convenient and efficient Hg²⁺ detection method. In this study, anthracene-based Hg²⁺ fluorescent probes AN-2S and AN-4S were synthesized by a dithioacetal reaction for the rapid and efficient detection of the Hg²⁺ concentration in water. Through molecular structure design and synthesis route optimization, the complexity and cost of the probe synthesis were greatly reduced. AN-2S and AN-4S had good water solubility, rapid response abilities and anti-interference abilities, and could specifically detect Hg²⁺ using “turn-off” or “turn-on” detection modes within 1 min. The AN-4S probe showed a wide linear response range (0~40 μmol/L) and high sensitivity (4.93 × 10⁻⁸ mol/L) to Hg²⁺ in 99% aqueous solutions, over a pH range of 5~13. The reaction mechanism between the probe and Hg²⁺ was determined using 1H NMR and FT-IR spectra and Job’s curves. It was proven that the AN-2S and AN-4S probes react with Hg²⁺ in a molar ratio of 1:1 or 1:2. The dual-detection mode enabled the probes to be used not only for the accurate quantitative detection of Hg²⁺ under a fluorescence spectrometer, but also for rapid qualitative analysis using a UV flashlight as a test strip, showing a broad practical application potential. Full article

Nuclear magnetic resonance (NMR) spectroscopy is gaining prominence as a vital quantitative method for sample analysis, with significant progress being made in the investigation of heteronuclei like phosphorus, a key element in numerous physiological functions. This paper provides a comprehensive review of the principles, methodologies, and applications of quantitative ³¹P nuclear magnetic resonance (qNMR) spectroscopy. It begins with an introduction to the fundamental principles of NMR spectroscopy, highlighting the specific advantages of qNMR and the unique properties of the ³¹P nucleus, including its high natural abundance and broad chemical shift range. While ¹H qNMR is widely used, signal overlap in complex mixtures can limit its accuracy. Additionally, this work explores diverse applications of ³¹P qNMR across fields such as food analysis, pharmaceuticals, and biology, emphasizing its contributions to real-time drug quantification, metabolomics, and environmental analysis. A key advantage of ³¹P NMR is its ability to provide exclusive detection and direct quantification of phosphorus in phosphorus-containing compounds. The internal standard method is favored for its simplicity, as it avoids the need for calibration curves, while the external standard method is better suited for natural products with established reference materials. This review aims to consolidate the applied prospects of ³¹P qNMR, emphasizing its potential to expand the horizons of quantitative detection technologies and facilitate advancements in future research and practical applications. Full article

Bisphenol A (BPA) is a commonly synthetic chemical mainly used in producing plastic items. It is an endocrine-disrupting compound that causes irreversible health and environmental damage. Developing a simple method for BPA effective quantitative monitoring is emergently necessary. Herein, a novel electrochemical sensor for BPA detection based on [(5,10,15,20-tetrakis(p-bromophenyl) porphyrinato] cadmium (II) [(CdTBrPP)] and gold nanoparticle (AuNPs)-modified screen-printed carbon electrode (SPCE) was elaborated. CdTBrPP was synthesized and then characterized with Ultraviolet–Visible Spectroscopy (UV/vis), Infrared Spectroscopy (IR), and Proton Nuclear Magnetic Resonance Spectroscopy (¹H NMR) to confirm its successful synthesis. After drop-coating AuNPs and CdTBrPP on the SPCE, the sensor performance was evaluated using square wave voltammetry (SWV), a linear response in a concentration range from 10⁻¹¹ M to 10⁻² M, with a low detection limit (LOD) of 9.5 pM. The CdTBrPP/AuNPs/SPCE sensor demonstrates a high selectivity and reproducibility, making it a promising candidate for developing a low-cost water-monitoring system for detecting BPA. Additionally, the proposed sensor effectively detected BPA in both tap and mineral water samples. Full article

Zinc is a trace element, which plays an important role in many biological processes. The deficiency of zinc will lead to many diseases. Thus, it is of great significance to develop fast and efficient quantitative detection technology for zinc ions. In this study, a novel fluorescence probe FP2 was designed for Zn²⁺ quantification based on pyrano[3,2-c] carbazole. The structure of FP2 was characterized by ¹HNMR, ¹³CNMR, HRMS, and X-ray diffraction. In the HEPES buffer solution, FP2 is responsive to Zn²⁺ and greatly enhanced. The pH value and reaction time were investigated, and the optimum reaction conditions were determined as follows: the pH was 7~9 and the reaction time was longer than 24 min. Under the optimized conditions, the concentration of FP2 and Zn²⁺ showed a good linear relationship in the range of 0~10 μM, and the LOD was 0.0065 μmol/L. In addition, through the ¹H NMR titration experiment, density functional theory calculation, and the job plot of FP2 with Zn²⁺ in the HEPES buffer solution, the binding mode of FP2 and Zn²⁺ was explained. Finally, the method of flame atomic absorption spectrometry (FAAS) and FP2 were used to detect the content of Zn²⁺ in the water extract of tea. The results showed that the FP2 method is more accurate than the FAAS method, which shows that the method described in this work could be used to detect the content of Zn²⁺ in practical samples and verify the practicability of this method. Full article

Phosphorus (P) is a crucial nutrient in lake ecosystems and organic phosphorus (Po) is a significant component. However, the distribution characteristics and migration behaviour of Po in ice–water–sediment systems under freezing and thawing conditions in cold and arid regions remain unclear. This study aims to investigate the forms of Po and its contribution to endogenous P pollution. We selected three lakes (Dai, Hu, and Wu Lake) and employed phosphorus nuclear magnetic resonance (³¹P-NMR) techniques to analyse the following: (1) The total phosphorus (TP) content, which was the highest in the water from Dai Lake (0.16 mg/L), with substantial seasonal variation observed in Wu Lake, where P content was four times higher in summer than in winter because of farmland drainage. (2) Eutrophication analysis, which indicated that Dai Lake had significantly higher eutrophication levels than Wu Lake, with P being the controlling factor in Dai Lake and both N and P in Wu Lake. The proportion of Po in the TP content was 90%, 70%, and 55% for Wu, Dai, and Hu Lake, respectively, indicating that Po was the main component of eutrophic lakes. (3) ³¹P-NMR, which revealed that orthophosphate (Ortho-P) and monoester phosphate (Mon-P) were the main P components in the winter, with a higher P content in Dai Lake. Ortho-P has a higher content in ice, indicating that inorganic phosphorus (Pi) migration is the main factor in ice–water media. Mon-P showed multiple peaks in Dai Lake, indicating a complex composition of adenosine monophosphate and glucose-1-phosphate. (4) The ice–water phase change simulation experiments, which showed that phosphate was the least repelled in ice, while pyrophosphate (Pyro-P) and macromolecular P were more repelled. Adding sediment enhanced the migration of P but did not change the repulsion of macromolecular P, suggesting the molecular structure as the main influencing factor. These results provide important scientific evidence for the quantitative analysis of Po pollution in lake water environments, aiding in P load reduction and risk prevention and control. Full article

Newly synthesized 7-chloro-4-aminoquinoline–benzimidazole hybrids were characterized by NMR and elemental analysis. Compounds were tested for their effects on the growth of the non-tumor cell line MRC-5 (human fetal lung fibroblasts) and carcinoma (HeLa and CaCo-2), leukemia, and lymphoma (Hut78, THP-1, and HL-60) cell lines. The obtained results, expressed as the concentration at which 50% inhibition of cell growth is achieved (IC₅₀ value), show that the tested compounds affect cell growth differently depending on the cell line and the applied dose (IC₅₀ ranged from 0.2 to >100 µM). Also, the antiplasmodial activity of these hybrids was evaluated against two P. falciparum strains (Pf3D7 and PfDd2). The tested compounds showed potent antiplasmodial activity, against both strains, at nanomolar concentrations. Quantitative structure–activity relationship (QSAR) analysis resulted in predictive models for antiplasmodial activity against the 3D7 strain (R² = 0.886; R_ext² = 0.937; F = 41.589) and Dd2 strain (R² = 0.859; R_ext² = 0.878; F = 32.525) of P. falciparum. QSAR models identified the structural features of these favorable effects on antiplasmodial activities. Full article

Herein, we report the synthesis and characterization of a novel Schiff base ligand, (Z)-5-((pyren-1-ylmethylene)amino)-2,4-dihydro-3H-pyrazol-3-one (PMDP). The characterization of ligand PMDP was carried out using ESI-MS, ¹H NMR, and UV–Visible spectroscopic techniques. As a probe, PMDP displayed a detectable, colorimetric colour shift in the presence of Cu²⁺ and Fe²⁺ ions. The solution was seen to have a light brown colour and to exhibit a fluorometric “turn off” response when Cu²⁺ and Fe²⁺ ions were present in a DMSO solution (HEPES 0.01 M, pH = 7.4) at room temperature. Job’s plot revealed that the PMDP binding ratio to Cu²⁺ and Fe²⁺ ions was in 1:2 ratio. In contrast to the other metal ions (Cd²⁺, Mn²⁺, Co²⁺, Na⁺, Ni²⁺, Cu⁺, Fe³⁺, Hg²⁺, Mg²⁺, Zn²⁺, K⁺, and V⁵⁺), the synthesised probe showed exceptional sensitivity and selectivity for detecting Cu²⁺ and Fe²⁺ metal ions. The results indicate that the detection limits for Cu²⁺ and Fe²⁺ are 0.42 μM and 0.51 μM, respectively. Furthermore, PMDP was efficiently utilised for the quantitative analysis of Cu²⁺ and Fe²⁺ in real water samples, RGB colour values in smart phones, logic gate construction, and cell imaging in HeLa cells. Full article

A study of the liquid–liquid extraction of ReO₄⁻ anions from hydrochloric acid solutions using the ionic liquid Aliquat 336 (QCl: trialkyl(C₈–C₁₀)methylammonium chloride) via the well-known method of slope analysis along with the determination of the process parameters is presented. This study employs CCl₄, CHCl₃ and C₆H₁₂ as diluents. This study was carried out at room temperature (22 ± 2) °C and an aqueous/organic volumetric ratio of unity. The ligand effect on the complexation properties of ReO₄⁻ is quantitatively assessed in different organic media. The organic extract in chloroform media is examined through ¹H, ¹³C and ¹⁵N NMR analysis as well as the HRMS technique and UV-Vis spectroscopy in order to view the anion exchange and ligand coordination in the organic phase solution. Final conclusions are given highlighting the role of the molecular diluent in complexation processes and selectivity involving ionic liquid ligands and various metal s-, p-, d- and f-cations. ReO₄⁻ ions have shown one of the best solvent extraction behaviors compared to other ions. For instance, the Aliquat 336 derivative bearing Cl⁻ functions shows strongly enhanced extraction as well as pronounced separation abilities towards ReO₄⁻. Full article

Tripropyl phosphate (TnPP) is a commonly used organic phosphate flame retardant in the textiles, plastics, and coating industries. Residues are commonly detected in samples from the environment and food. The availability of certified reference materials (CRMs) is essential to ensure the accuracy and traceability of detection results. In this study, a comprehensive characterization of a CRM for TnPP was carried out, and its purity was evaluated using two distinct methodologies: mass balance (MB) and quantitative nuclear magnetic resonance spectroscopy (qNMR). In the MB method, the levels of structurally related organic impurities are 1.37 mg/g. The water content was determined to be 3.16 mg/g, while inorganic impurities were found to be 0.87 mg/g, and no residual organic solvents were detected. Benzoic acid and monocrotophos were chosen as internal standards for ¹H-qNMR and ³¹P-qNMR, respectively. The purity of the TnPP CRM was assessed as 994.6 mg/g, 994.1 mg/g, and 993.5 mg/g using MB, ¹H-qNMR, and ³¹P-qNMR techniques, respectively. The verified purity of the TnPP CRM was ultimately determined to be 994.1 mg/g, with an expanded uncertainty of 3.4 mg/g (k = 2), ensuring traceability to the International System of Units (SI). This CRM can be effectively utilized for preparing calibration solutions suitable for the routine monitoring of TnPP residues in plastics and food samples. Full article

The reaction of (Z)-5-phenyl-1,3-di-p-tolylpent-2-en-4-yn-1-ol (1) with trimethylsilyl chloride in dichloromethane at ambient temperature gave a dimeric ether compound 2 in 30% yield. Subsequently, heating 2 in toluene under refluxing temperature rendered the title compound quantitatively. The structure of this tricyclic-fused compound was characterized using NMR, mass spectroscopy, and X-ray crystallography. This unique linear tricyclic fused furan framework is reported for the first time. Full article