Search Results (410)

To investigate the electron-donating substitution effect on spin crossover (SCO) and electrochemical behaviors for homoleptic trivalent metal complexes with 2,2′-azobisphenolate (azp) ligands, the known 2,2′-azobisphenol with 5,5′-dimethyoxy substituents (H₂L^OMe) was synthesized and characterized by NMR spectroscopy and single-crystal X-ray diffraction (SCXRD). The homoleptic Fe^III and Al^III complexes 1-OMe and 2-OMe were prepared along with the homoleptic Fe^III complex with 5,5′-dimethyl-substituted azp ligands 1-Me. The temperature dependence of magnetic susceptibility and SCXRD revealed that 1-OMe exhibits incomplete gradual SCO with the rotational motion of the ligands. Cyclic voltammograms and their simulations revealed that both the Fe^III complex 1-OMe and the Al^III complex 2-OMe exhibit reversible one-electron oxidation waves, indicating that the introduction of the methoxy group enhances the stability of the oxidized species of the complexes. DFT calculations revealed that the oxidation waves for both the Fe^III and Al^III complexes are ligand-centered, while the reduction wave for the Fe^III complexes 1-OMe and 1-Me is metal-centered. In addition, the stability of the oxidized complex species arises from the resonance effect of the methoxy group. Full article

The development of hybrid bifunctional chelators (BFCs) capable of efficiently coordinating both diagnostic and therapeutic radionuclides remains a major challenge in theranostic radiopharmaceutical design. Herein, two novel hybrid NOTA-derived chelators, NO2A-2C-AHM and NODAGA-HM, were developed from the previously reported NO2A-AHM BFC to improve the coordination of ¹⁷⁷Lu while preserving efficient Al¹⁸F labeling. Both ligands were successfully synthesized and fully characterized by NMR and mass spectrometry analyses. Their coordination properties toward {AlF}²⁺ and Lu³⁺ were thoroughly investigated by molecular modeling, non-radioactive complexation, and radiolabeling studies. Both chelators efficiently formed AlF complexes, exhibiting high complexation yields and successful Al¹⁸F radiolabeling with good stability. In contrast, only NODAGA-HM efficiently coordinated Lu³⁺, whereas NO2A-2C-AHM failed to form stable Lu complexes under both non-radioactive and radiolabeling conditions. Optimized radiolabeling of NODAGA-HM with ¹⁷⁷Lu afforded high radiochemical conversion, consistent with the molecular modeling predictions. These results demonstrate that the spatial positioning of the additional donor arm, rather than linker elongation alone, is a key determinant for efficient coordination of larger trivalent radiometals. Thus, NODAGA-HM emerged as the most promising candidate for further development of targeted radiopharmaceuticals based on the Al¹⁸F/¹⁷⁷Lu theranostic approach. Full article

Lost circulation is a major technical bottleneck restricting safe and efficient while-drilling plugging operations. Polyacrylamide gel has become a widely used plugging material in drilling engineering. Unlike rigid, cement-like plugging materials, the gel system formed in this study does not develop a hardened, consolidated structure capable of anchoring or binding the drill bit during subsequent drilling operations, thereby eliminating the risk of bit-sticking. Nevertheless, the gel possesses sufficient elastic (viscoelastic) structural strength—reflected in its storage modulus (G′)—to effectively resist deformation and displacement under differential pressure, thereby providing reliable fracture-sealing performance, which effectively prevents pipe-sticking risks. However, high-concentration PAM molecular chains easily stretch and entangle in aqueous solution, triggering an abnormal increase in initial viscosity and poor pumpability. Although Ca²⁺ can inhibit the premature water absorption and thickening of PAM to maintain system fluidity, an excessively high Ca²⁺ concentration will suppress the hydrolysis of Al³⁺ and hinder the formation of hydroxyaluminum—the key crosslinking component of the gel system. To solve the above contradiction, a CaCl₂-tolerant delayed-release crosslinker was synthesized. ZnO was selected as a carrier to adsorb and immobilize polynuclear hydroxyaluminum complexes hydrolyzed from an inorganic aluminum crosslinker at 70 °C, realizing the controlled delayed release of the crosslinker. The microstructures and chemical bonding were characterized by SEM elemental mapping, FT-IR and ²⁷Al MAS NMR. The results confirm that abundant aluminum species are uniformly loaded on the ZnO surface to form stable Zn–O–Al covalent bonds, and the loaded aluminum exists mainly in the form of hydroxyaluminum. With increasing temperature, the Zn–O–Al bonds gradually break and slowly release hydroxyaluminum species. A novel delayed crosslinking gel system was ultimately optimized, composed of 6% CaCl₂, 10.4% PAM and 3% ZnO loaded with polynuclear hydroxyaluminum. The system exhibits excellent delayed gelation behavior, with a fluidity loss time longer than 120 min and a gelation time over 200 min. It maintains favorable fluidity within 30–90 °C, and the formed gel shows a stable elastic modulus (G′) and viscous modulus (G″). Moreover, the system achieves a plugging rate of more than 90% and a breakthrough pressure above 5 MPa, demonstrating superior comprehensive plugging performance for while-drilling plugging applications. Full article

Background: This study evaluated the effects of aging and subsequent autoclave treatment on the proton nuclear magnetic resonance (¹H NMR) spectral-feature profile and biological activities of lychee pulp extracts. Methods: Dried lychee (DL), aged lychee (AL), and autoclave-treated aged lychee (ATAL) extracts were compared using ¹H NMR spectroscopy, total phenolic content (TPC), total flavonoid content (TFC), antioxidant assays, carbohydrate-hydrolyzing enzyme inhibitory assays, and endothelial cell viability. Results: Sixteen phytochemical spectral features were putatively annotated, and their relative signal intensities differed among the extracts (p < 0.001). Relative to DL, ATAL exhibited higher signal intensities for most features, including taxifolin (8.32-fold) and procyanidin B2 (7.44-fold), whereas epicatechin was particularly prominent in AL (12.31-fold). TPC increased from 0.53 ± 0.07 mg gallic acid equivalents (GAE)/g extract in DL to 8.39 ± 0.19 and 9.07 ± 0.10 mg GAE/g extract in AL and ATAL, respectively. AL and ATAL also showed higher TFC and antioxidant activities than DL. The α-amylase IC₅₀ values were 247.00 ± 45.00, 129.17 ± 8.56, and 126.27 ± 3.90 mg/mL for DL, AL, and ATAL, respectively, while the corresponding α-glucosidase IC₅₀ values were 187.93 ± 8.20, 66.71 ± 6.84, and 50.30 ± 2.72 mg/mL. No significant reduction in endothelial cell viability was detected after multiplicity adjustment. Exploratory principal component analysis (PCA) explained 99.8% of the total variance and revealed distinct processing-associated spectral-feature profiles. Conclusions: Aging followed by autoclave treatment enhanced the phytochemical profile, antioxidant activity, and in vitro carbohydrate-hydrolyzing enzyme inhibition of lychee pulp extracts. Full article

1,2,3-Triazole units with their structural and photophysical properties are well-suited for the development of chemosensors for ion sensing. Synthetic approaches make it extremely easy to modify this core with just a few steps to control ion selectivity and response-signal output. The current study examines how 8-(4-phenyl-1H-1,2,3-triazol-1-yl)quinoline, a quinoline–triazole–phenyl (QTP) construct, responds differentially to Cu²⁺ and Al³⁺ ions. QTP provides distinct fluorescent signals in acetonitrile in the presence of Cu²⁺ versus Al³⁺, a turn-off response with Cu²⁺ and blue-to-green output with Al³⁺. Spectroscopic studies quantify the selectivity of the sensor for these species with respect to other ions and reveal a stoichiometric ratio of 1:1 for sensor:Cu²⁺ and 2:1 for sensor:Al³⁺. NMR titration studies suggest that Cu²⁺ is detected via coordination of the quinolinyl and triazolyl nitrogens, while Al³⁺ is detected through coordination of the quinoline nitrogen. Overall, QTP displays a selectivity for Al³⁺ relative to Cu²⁺ over other cations in this investigation. Full article

Developing a water-soluble and chlorine-free palladium compound to replace conventional PdCl₂ or Pd(NO₃)₂ as the precursor for Pd-based catalysts remains both challenging and of considerable significance for highly efficient degradation of volatile organic compounds (VOCs). Herein, we report a facile synthetic route to such a Pd compound, (NH₄)₂[Pd(C₂O₄)₂]·2H₂O (denoted as Pd-X5), via a three-step reaction starting from PdCl₂, under mild and readily controllable conditions, rendering the process amenable to industrial manufacture. The molecular structure of Pd-X5 was confirmed mainly by elemental analysis, FT-IR, and ¹³C NMR. The overall yield was greater than 95% and the content of residual chloride was reduced to below 100 ppm. Pd-X5 exhibited high water solubility of 350 g L⁻¹. Subsequently, Pd-X5 was used as a catalytic precursor, and a Pd/Al₂O₃ catalyst was prepared by an impregnation technique and evaluated for its catalytic performance in the degradation of VOCs. Compared with Pd(NO₃)₂-derived Pd/Al₂O₃, the Pd-X5-based catalyst exhibited markedly enhanced activity for the oxidation of CH₄ and C₃H₈ at different temperatures and under different contents of water vapor, indicating that Pd-X5 is superior to Pd(NO₃)₂ as a catalytic precursor and has potential application in the production of Pd-based catalysts. Full article

Ni-doped amorphous Al₂O₃ catalysts were successfully prepared for the one-step reduction of nitrobenzene to azoxybenzene using NaBH₄ as hydrogen donors under mild conditions. The amorphous Ni₁Al₈₇O_x catalyst achieved a highly efficient azoxybenzene production rate of 1.89 mol·g-Ni⁻¹·h⁻¹, significantly outperforming its Ni/γ-Al₂O₃ counterpart. On the basis of the MAS NMR and XPS characterization results, the enhanced catalytic performance is associated with Ni incorporation during the preparation of amorphous Ni₁Al₈₇O_x, which introduces abundant unsaturated pentacoordinate Al species with oxygen vacancies and stabilizes Ni^δ+ sites against over-reduction. Notably, Ni₁Al₈₇O_x loaded on commercial ZSM-5 supports maintained an azoxybenzene yield of 9.02 mol·g-Ni⁻¹·h⁻¹, highlighting the strong potential for further scalable applications. Full article

The natural mineral sinhalite, MgAlBO${⁠}_4$, was investigated by means of single-crystal NMR spectroscopy. In its orthorhombic space group, the aluminium and boron atoms occupy Wyckoff positions $4b$ and $4c$, but the specific site symmetry of the boron atoms situated on a mirror plane leads two only two instead of four magnetically inequivalent atoms per site. This structural feature also restricts the corresponding NMR interaction tensors and reduces known assignment ambiguities regarding the NMR resonances of ${⁠}^{27}$Al and ${⁠}^{11}$B to distinct atomic positions. Comparing the experimentally determined eigenvectors of the quadrupolar coupling tensors with the results of DFT calculations for the electric field gradients further condensed the remaining options and delivered the full quadrupolar coupling tensors for both nuclides in the crystal structure of sinhalite. Full article

Sesquiterpenoids are widely distributed in the genus Dysoxylum (Meliaceae) and have attracted attention because of their diverse biological activities, including antibiofilm properties. This study aimed to isolate and characterize sesquiterpenoids from the n-hexane extracts of Dysoxylum acutangulum Miq. and Dysoxylum cauliflorum Hiern twigs, followed by evaluation of their antibiofilm activity against Streptococcus mutans. Chromatographic separation of the n-hexane extract of D. acutangulum afforded spathulenol (1), β-caryophyllene oxide (3), and a mixture of epimeric sesquiterpenoids consisting of 10-oxo-isodauc-3-en-15-al (2a, major) and sinulin A (2b, minor), while humulene diepoxide A (4) was isolated from D. cauliflorum. Structural elucidation was carried out using MS, IR, and extensive NMR spectroscopic analyses, and by comparison with reported data. The major and minor epimers of compound 2 were distinguished based on diagnostic NMR signal intensities and comparison with literature data. Notably, all isolated compounds are reported herein for the first time from their respective Dysoxylum species. Compound 1, the epimeric mixture 2a/2b, and compound 4 exhibited weak antibiofilm activity against S. mutans, with minimum biofilm inhibitory concentration (MBIC) values ranging from 250 to 500 µg/mL, whereas chlorhexidine exhibited superior antibiofilm activity at 62.5 µg/mL. Molecular docking against Sortase A and GtfB revealed moderate binding affinities and suggested plausible interactions with biofilm-associated targets. These findings provide additional chemotaxonomic information on Dysoxylum species and preliminary insight into the antibiofilm potential of their sesquiterpenoids, particularly for compounds with limited previous antibiofilm reports. Full article

The catalytic isomerization of glucose to fructose is a pivotal step in the valorisation of lignocellulosic biomass. In this study, polyaluminium chloride (PAC), a low-cost, industrially available material characterised by polynuclear aluminium–oxo species, is investigated for the first time as an alternative catalyst for this transformation. The catalytic performance of PAC was systematically investigated by varying the temperature (70–130 °C), solvent (pure water, H₂O:MeOH 1:1 or 4:1) and reaction time (30–120 min). A fructose yield of up to 55% with a selectivity of 85% was obtained by using PAC at 120 °C in H₂O:MeOH 1:1 for 120 min, confirming its effectiveness in promoting glucose isomerization to fructose. Mechanistic insights and quantitative monitoring were achieved using benchtop NMR spectroscopy. ²⁷Al-NMR of PAC in aqueous solution exhibits two main signals at 1.12 ppm (attributed to the hexacoordinated Al complex) and at 63.3 ppm (associated with a tetrahedral Al centre typical of the Al₁₃ Keggin-type cluster). With the increase in temperature, as well as by changing the reaction media from pure aqueous to a mixed aquo-alcoholic system, new Al species were generated that are more reactive than the starting AlCl₃∙6H₂O and PAC. Overall, this work demonstrates that PAC represents a viable, scalable, and more sustainable alternative to conventional aluminium-based catalysts, offering a promising route toward more efficient biomass conversion processes. Full article

While the petroleum industry undergoes structural adjustments in supply and demand alongside a green and low-carbon transition, water drilling mud generated during oil extraction poses severe environmental challenges. Consequently, addressing the solid waste pollution and disposal issues associated with drilling mud has become critical. In this study, ZSM-5 zeolite was synthesized using water drilling mud as a silicon and aluminum source, inexpensive n-butylamine as a template agent, and a combined approach of alkali-melting activation pre-treatment and seed-directed hydrothermal synthesis. By adjusting key parameters such as water content, template agent dosage, and seed addition, optimal synthesis conditions were determined. Based on these conditions, a series of ZSM-5 zeolites with varying silicon-to-aluminum ratios were synthesized. Characterization results from XRD, TEM, SEM, and N₂ adsorption–desorption experiments revealed that all prepared samples exhibited high crystallinity, regular morphology, and high specific surface area. ²⁷Al MAS NMR results indicated that almost aluminum species were located at the framework structures with four-coordination. In the 1,3,5-triisopropylbenzene cracking reaction, the conversion rate increased with decreasing silicon-to-aluminum ratio, consistent with variations in acid amount. These findings achieve high-value utilization of waste drilling mud, offering a novel pathway for low-cost synthesis of high-performance ZSM-5 zeolite. This breakthrough injects fresh momentum into the petroleum refining industry’s green sustainable development, fostering a win–win scenario that harmonizes ecological conservation with industrial profitability. Full article

Diphenylamine is an important organic chemical intermediate, and its industrial synthesis is mainly achieved through the continuous condensation of aniline. In this study, Hβ zeolite was modified with citric acid, and its catalytic performance in the aniline condensation reaction for diphenylamine synthesis was systematically investigated. The crystal structure, acidic characteristics, pore properties, and Si/Al composition of the catalysts were comprehensively characterized by means of XRD, SEM, BET, Py-IR, ICP, and ²⁷Al MAS NMR. The catalytic activities of Hβ zeolites modified with different concentrations of citric acid were evaluated in a micro fixed-bed reactor, and the structure–activity relationship was systematically discussed in combination with the characterization results. The results demonstrate that the Hβ zeolite modified with 1.5 mol/L citric acid achieves precise matching with the aniline condensation reaction in terms of crystal structure integrity, pore channel parameters, acid property distribution, and Si/Al ratio regulation. Compared with the unmodified catalyst, its catalytic activity is improved by approximately 28%, with a diphenylamine selectivity of 100%. This study proposes a modification mechanism of Hβ zeolite by citric acid. Full article

Using strategies employed in synthetic chemistry, we investigated the chemicals found in lithium iron phosphate (LFP) spent battery via an initial dichloromethane (DCM) extraction of the individual cathode and anode. The pre- and post-treated electrodes and DCM extracts were examined using a range of analytical techniques. A total of 26 compounds were identified, which included the following: (1) some of the benchmark materials, LFP, lithium hexafluorophosphate (LIPF₆), polyvinylidene fluoride (PVDF), graphite and carbon black; (2) NMR spectroscopy of DCM extract revealed five main chemicals, which were ethylene and propylene carbonate solvents, LiPF₆, lithium tetrafluoroborate (LiBF₄), and an unknown fluorochemical; (3) analysis of the water-treated DCM extract revealed 21 chemicals by GCMS, several fluorochemicals; (4) 12 chemicals were found in both cathode and anode and three only in the anode; (5) only 13 of the 21 chemicals could be properly named, whilst four had some notable functionality and three could not be identified; and (6) ICP analysis revealed high levels of Al, Cu, Fe, V, and Zn in both electrodes and spent electrolyte. The high number of chemicals present in the spent electrolyte and electrodes suggest battery manufacturers use many proprietary chemicals to enhance battery properties. This procedure allows insight and identification of chemicals present in waste LIBs which will require advanced chemical techniques to recover high yields and purity of recycled materials and the need to dispose of hazardous waste. Full article

A new selective fluorescent probe based on a vitamin B₆ derived hydrazone was synthesized and characterized for the detection of Al³⁺ and Ga³⁺ ions. The probe’s selectivity and sensitivity were evaluated using UV-Vis, fluorescence, and NMR spectroscopy in a buffered DMSO/water solution, complemented by density functional theory (DFT) calculations to elucidate the electronic structure and coordination modes of the resulting complexes. The probe exhibited a notable “turn-on” fluorescence response upon binding Al³⁺ and Ga³⁺, with emission maxima at 466 nm and 477 nm, respectively, and detection limits as low as 48 nM for Al³⁺ and 33 nM for Ga³⁺. The probe showed high selectivity for these ions over a wide range of competing cations and anions, forming stable 1:1 complexes with log β′ values of 5.98 for Al³⁺ and 6.28 for Ga³⁺. DFT calculations revealed a tridentate coordination mode via the phenolic oxygen, azomethine nitrogen, and carbonyl oxygen, with distinct electronic transitions for each complex, including a ligand-to-metal charge transfer character in the Ga³⁺ complex. The probe demonstrates reversibility and excellent solution stability, offering a simple and sensitive platform for the environmental and biological monitoring of aluminum(III) and gallium(III) ions. Full article

The selective removal of beryllium from aqueous matrices remains a critical environmental and industrial challenge due to beryllium’s extreme toxicity, strong hydration chemistry, and the difficulty of separating Be²⁺ from chemically similar cations such as Al³⁺. In this study, a novel multidentate Schiff-base porous organic adsorbent, TFP-HEDA, was synthesized by condensation of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (TFP) with N-(2-hydroxyethyl)ethylenediamine (HEDA) followed by urethane post-functionalization and systematically characterized by FTIR, ¹H/¹³C NMR, MALDI-TOF MS, elemental analysis, BET surface area analysis (617 m² g⁻¹), PXRD, and XPS. Batch adsorption experiments demonstrated rapid Be²⁺ uptake, achieving 90% removal within 20 min and equilibrium within 30 min. Among the isotherm models evaluated, the Langmuir model yielded the highest statistical consistency (R² = 0.9835, RMSE = 5.15 mg g⁻¹, χ² = 1.137) with a predicted maximum adsorption capacity of 163.93 mg g⁻¹ agreeing closely with the experimental value of 163.67 ± 6.42 mg g⁻¹ (deviation < 0.2%); this mathematical adequacy is interpreted as compatibility with a finite, saturable set of inner-sphere coordination sites rather than confirmation of a flat, energetically uniform surface, with chemisorption independently and more rigorously established by Dubinin–Radushkevich analysis (E = 28.87 kJ mol⁻¹) and post-adsorption FTIR and XPS evidence. Dubinin–Radushkevich analysis confirmed a chemisorption mechanism with mean adsorption energy E = 28.87 kJ mol⁻¹, consistent with inner-sphere Be²⁺–O/N coordination. Process optimization using response surface methodology based on a central composite design achieved 99% Be²⁺ removal at pH 5, an adsorbent dose of 60 mg/20 mL, and a contact time of 30 min (R² = 0.9892). Post-adsorption FTIR, XPS, BET, and TGA characterization confirmed framework integrity and the inner-sphere multidentate coordination mechanism. TFP-HEDA retained 82.4% of its initial capacity after nine adsorption–desorption cycles, demonstrating practical regenerability for Be²⁺ recovery applications. Full article