Search Results (383)

A novel dual-imidazoline ring quaternary ammonium salt corrosion inhibitor (TN-IM) was rationally synthesized via a three-step sequential reaction, using hydroxyethyl ethylenediamine and tetradecanedioic acid as starting materials, with benzyl chloride as the quaternizing reagent. The synthetic process involved amidation at 160 °C for 4 h, cyclization at 220 °C for 3 h, and quaternization at 70 °C for 3 h, respectively. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance were employed to characterize the chemical structure of TN-IM, confirming its successful synthesis. The corrosion inhibition performance of TN-IM was evaluated by the static weight loss method and electrochemical measurements, while the corrosion products and surface morphology of N80 carbon steel were analyzed via energy-dispersive X-ray spectroscopy and scanning electron microscopy. Static weight loss tests conducted in 3.5 wt% of a NaCl solution saturated with 0.6 MPa CO₂ at 60 °C for 24 h revealed that TN-IM at a concentration of 0.15 mmol/L exhibited a corrosion inhibition efficiency 1.86% higher than that of a single-imidazoline ring quaternary ammonium salt inhibitor. Potentiodynamic polarization measurements demonstrated that TN-IM functions as a mixed-type corrosion inhibitor, with a predominant inhibitory effect on the anodic reaction on N80 steel. Electrochemical impedance spectroscopy results indicated that TN-IM molecules can adsorb onto the active sites of the N80 surface, thereby retarding the corrosion process by suppressing the charge transfer step in the electrochemical corrosion reaction. This study establishes a new paradigm for the synthesis of high-efficiency imidazoline-based CO₂ corrosion inhibitors with multiple adsorption sites, holding significant implications for corrosion control in harsh industrial environments. Full article

Electronics evolution drives SMMs as a frontier, overcoming conventional magnetic material limits via molecular spin coupling. Two relevant Co(II) mononuclear complexes, [Co(MOP)₄(N₃)₂] (1) and [Co(MSP)₄(N₃)₂] (2) (MOP = 4-methoxypridine and MSP = 4-methylthiopyridine) were synthesized through changing the substituents of ligands. The Co(II) ions in the two complexes show octahedron coordination geometries. The replacement of the O to S in the equatorial plane leads to different Jahn–Teller effect because of the shorter Co(II)-N in the equatorial plane, resulting in the significantly different slow relaxation process confirmed by ab initio calculation. The results confirm the Co(II) ion is sensitive to ligand field. Full article

This study employs effective field theory to investigate the magnetic properties of the Carbon-60 fullerene cage (C₆₀). The analysis shows that the magnetic behavior of the C60 molecule mirrors that of its sixty constituent carbon atoms, a phenomenon attributed to the molecule’s unique cage geometry and defined herein as the “identic magnetic effect” (IME). Furthermore, thermodynamic quantities, including magnetic susceptibility, specific heat, and internal energy, exhibit dual peaks at the coercive field points when the temperature is below the critical threshold (T < Tc). As the temperature exceeds this threshold (T > Tc), these peaks coalesce into a single maximum. These findings show good quantitative agreement with experimental phase transition characteristics, reflecting the magnetic behavior induced by the C₆₀ cage geometry. IME behavior can open the door to modeling and produce a new class of IME sensors (IMESs). Full article

Aptamers are powerful tools for detecting and analyzing biomolecules that consist of proteins or nucleic acids. However, their application to aptamers against viroids—highly structured self-replicating RNAs—has not yet been explored. In this study, a magnetic bead- and high-throughput sequencing-based SELEX (MB-HTS-SELEX) protocol for selecting potential aptamers against potato spindle tuber viroid (PSTVd) is presented. Full-length biotinylated-PSTVd RNA was transcribed in vitro, immobilized on streptavidin-coated magnetic beads, and incubated with a library of ~3.32 × 10¹⁴ molecules of random single-stranded oligo-DNAs (oligo-ssDNAs) of 20, 30, or 40 nucleotides (L20, L30, or L40, respectively) flanked by primer binding sites for downstream PCR amplification. Simultaneous biotin labeling of the anti-aptamer strand of the resulting double-stranded DNA (dsDNA) amplicons facilitated strand separation using streptavidin-coated magnetic beads. After 10 selection rounds, high-throughput sequencing, followed by bioinformatics analysis of the generated sequences, allowed for the detection of several enriched sequences, representing putative PSTVd-binding aptamers. Subsequent pull-down assays showed that the most abundant oligo-ssDNA in L30 was docked on PSTVd molecules. This combination method may ameliorate the selection of high-affinity aptamers against PSTVd, reduce the number of selection cycles, time, and other costs of aptamer production, thereby promoting future massive and cost-effective viroid detection and characterization. Full article

The ligand-driven self-assembly of metal clusters offers a powerful strategy for constructing discrete molecular architectures with tunable magnetic and structural properties. By judiciously selecting appropriate multidentate ligands, researchers can direct the formation of polynuclear metal assemblies with diverse nuclearities, geometries, and topologies. Coordination-driven processes commonly stabilize such assemblies where multidentate ligands operate as templates and linkers. These will also determine how the metal centers are arranged in space and how they connect to each other. These clusters can take on shapes that range from basic bridging dimers to more complicated icosahedral and cubane-type motifs. They often have excellent symmetry and strong frameworks. Magnetically, these clusters are a great place to study exchange interactions, spin frustration, and the behavior of single-molecule magnets (SMMs). The magnetic characteristics depend on things like the type of metal ions, the bridging ligands, the overall shape, and the local coordination environment. Interestingly, a large number of ligand-assembled clusters exhibit high spin ground states and slow magnetization relaxation, which makes them attractive options for quantum information storage and molecular spintronic devices. This review connects coordination chemistry, supramolecular design, and molecular magnetism of pyridine–amine–carboxylate frameworks, offering insights into fundamental magnetic phenomena and guiding the development of next-generation functional materials. Continued exploration of ligand frameworks and metal combinations holds the potential to yield novel clusters with enhanced or unprecedented magnetic characteristics. Full article

Lanthanide-based single-molecule magnets are promising candidates for potential applications. Their magnetism is governed by ligand-field splittings, which may require up to 27 ligand-field parameters for accurate modeling. Determining these parameters reliably from measured data is a major challenge, for which machine learning approaches offer promising solutions. We provide an overview of these approaches and present our perspective on addressing the inverse problem relating experimental data to ligand-field parameters. Previously, a machine learning architecture combining a variational autoencoder (VAE) and an invertible neural network (INN) showed promise for analyzing temperature-dependent magnetic susceptibility data. In this work, the VAE-INN model is extended through data augmentation to enhance its tolerance to common experimental inaccuracies. Focusing on second-order ligand-field parameters, diamagnetic and molar-mass errors are incorporated by augmenting the training dataset with experimentally motivated error distributions. Tests on simulated experimental susceptibility curves demonstrate substantially improved prediction accuracy and robustness when the distributions correspond to realistic error ranges. When applied to the experimental susceptibility curve of the complex ${\mathrm{Al}}_2^{\mathrm{III}}$${\mathrm{Er}}_2^{\mathrm{III}}$, the augmented VAE–INN recovers ligand-field solutions consistent with least-squares benchmarks. The proposed data augmentation thus overcomes a key limitation, bringing the ML approach closer to practical use for higher-order ligand-field parameters. Full article

High-resolution NMR spectroscopy is the leading method for determining nuclear magnetic moments. It is designed to measure stable nuclei, which can be investigated in macroscopic samples. In this work, we discuss the progress in research into light nuclei from the first three periods of the Periodic Table and several selected heavy nuclides. The ¹H and ³He nuclear magnetic moments, established using the new double Penning trap facility, are also considered. Both nuclei can be used as references in gaseous mixtures. Gas-phase NMR spectroscopy enables precise measurements of the frequencies and shielding constants of isolated single molecules. They can be used to determine new, accurate nuclear magnetic moments of nuclides in stable, gaseous substances. Particular attention is paid to the importance of diamagnetic corrections for obtaining accurate results. Finding precise diamagnetic corrections—shielding factors —even for light nuclei in molecules is a significant challenge. To date, nuclear moments have been obtained primarily from experimental data. The theoretical approach is mostly unable to predict these values accurately. Some remarks are also made on pure theoretical treatments of nuclear moments. Full article

Coordination complexes play a crucial role in modern research. 4-benzopyranone-2-carboxylic acid is a fascinating class of molecules with numerous applications, including the synthesis of pharmaceuticals and valuable chiral compounds. Antibacterial and tuberculostatic medicines, HIV protease inhibitors, intermediates in organic synthesis, and organic catalysis are only a few of the biological applications of chiral complexes. In this study, the synthesis of four metal complexes, C₃₀H₂₈N₂NiO₁₂ [Ni(bzpyr)₂(py)₂(H₂O)₂] (I), C₃₀H₂₄CoN₂O₁₀ [Co(bzpyr)₂(py)₂(H₂O)₂] (II), C₂₀H₂₀O₁₃Zn [Zn(bzpyr)₂(H₂O)₃] (III), and C₃₀H₂₂CuN₂O₉ [Cu(bzpyr)₂(py)₂(H₂O)] (IV), is reported via direct reactions of 4-benzopyranone-2-carboxylic acid with metal salts and pyridine in anhydrous ethanol. Single-crystal X-ray diffraction analysis revealed that complexes I and II crystallize in the chiral space group P-1, whereas III and IV crystallize in the centrosymmetric space group P2₁/c. The structures of these complexes were further characterized by infrared spectroscopy, UV-Visible Diffuse Reflectance Spectroscopy, electrospray ionization mass spectrometry (ESI-MS), elemental analysis, nuclear magnetic resonance, electron paramagnetic resonance spectroscopy and single-crystal X-ray diffraction. In addition, the cytotoxic activities of complexes I–IV were evaluated against the human tumor cell lines K562, A549, HepG2, MDA-MB-231, and SW480, and molecular docking studies were conducted on the four complexes. Full article

Background/Objectives: The poor aqueous solubility of curcumin (CUR) limits its pharmaceutical application. Although amorphization can enhance its solubility, the amorphous form often exhibits insufficient physical stability. Co-amorphization, particularly drug–drug co-amorphous (CAM) formation, offers a promising approach to improve solubility, stability, and therapeutic efficacy. This study aimed to prepare and evaluate two CUR-based CAM systems using isoquinoline alkaloids berberine hydrochloride (BER) and palmatine hydrochloride (PAL) as co-formers to achieve simultaneous stabilization and synergistic bioactivity. Methods: CUR-BER and CUR-PAL CAM systems were prepared via rotary evaporation under vacuum at a 1:1 molar ratio. The solid-state properties were characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM), and ¹³C solid-state nuclear magnetic resonance spectroscopy (ssNMR). Dissolution, solubility, and stability studies were conducted, while antioxidant and anticancer activities were assessed by DPPH/ABTS⁺ radical-scavenging and MTT assays using HT-29 colorectal cancer cells. Results: PXRD and DSC confirmed the formation of single-phase amorphous systems with higher glass transition temperatures, indicating strong intermolecular interactions between CUR and BER/PAL. ¹³C ssNMR spectroscopy evidenced hydrogen-bond formation between the enolic hydroxyl moiety of CUR and the methoxy oxygen atoms in BER or PAL molecules. Both CAM systems significantly enhanced the solubility and dissolution rate of CUR, with CUR-PAL CAM showing up to a 15.1-fold solubility improvement. The CAM systems also displayed superior thermal stability, photolytic stability, and improved short-term humidity resistance, together with enhanced antioxidant and anticancer activities compared with pure amorphous CUR. Conclusions: Co-amorphization of CUR with isoquinoline alkaloids effectively improved solubility, stability, antioxidant and anticancer activities, representing a promising strategy for the rational design of multifunctional amorphous CUR-based drug formulations. Full article

Lanthanide-based single-molecule magnets (Ln-SMMs) showing stimuli-responsive changes in photoluminescence (PL) and magnetic properties are attractive for their potential applications in information storage and molecular devices. In this work, we report two mononuclear complexes, namely, Dy(SCN)₂(NO₃)(Cl-depma)₂(4-hpy)₂ (Dy-Cl) and Dy(SCN)₂(NO₃)(Br-depma)₂(4-hpy)₂ (Dy-Br), where X-depma represents 10-X-9-diethylphosphinomethylanthracene (X = Cl, Br) and 4-hpy is 4-hydroxypyridine. Both contain face-to-face π-π-interacted anthracene rings and exhibit yellow-green excimer emission. Unlike the other related Dy–anthracene complexes without a halogen substituent, Dy-Cl and Dy-Br cannot undergo photocycloaddition reaction under UV-light irradiation. However, they exhibited remarkable grinding-induced changes in luminescence. Magnetic studies revealed that Dy-Cl and Dy-Br show SMM behavior under zero dc field with the effective energy barriers (U_eff/k_B) of 259 K and 264 K, respectively. We also investigated the effect of pressure on the magnetic properties of Dy-Br and observed a reduction in the magnetization value, narrowing of the butterfly-shaped hysteresis loop, and acceleration of the magnetic relaxation under 1.09 GPa. The results demonstrate that introducing a halogen substituent into an anthracene group may pose significant influences on the photophysical and photochemical properties of the complexes. In addition, pressure may be a promising external stimulus to modulate the PL and SMM behaviors of Dy–anthracene complexes. Full article

Triarylmethyl radicals (TAMs) have recently emerged as highly effective polarizing agents in dynamic nuclear polarization (DNP) under viscous conditions, enabling substantial hyperpolarization via the solid-effect (SE) DNP mechanism even at room temperature. A comparable, though less pronounced, enhancement was observed for BDPA radicals embedded in phosphocholine-based lipid bilayers. Given the increasing interest in elucidating the structure and dynamics of biopolymers and their high-molecular-weight assemblies—such as cell membranes—this study focuses on the design, synthesis, and characterization of paramagnetic agents tailored for DNP-based structural biology. To this end, we synthesized a series of TAM derivatives functionalized with lipophilic substituents and characterized their magnetic resonance properties, including isotropic hyperfine interaction (HFI) constants on carbon nuclei and electron spin relaxation times (T₁ and T_m) at low temperatures (80 K). Echo-detected EPR spectra and electron spin echo envelope modulations (ESEEM) were recorded for novel TAM incorporated into liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). These low-temperature measurements revealed that the radicals are localized either at the liposome surface or within the lipid bilayer, ensuring optimal accessibility to water molecules. Crucially, the presence of a single cholesterol moiety provides strong noncovalent anchoring within the hydrophobic core of the bilayer. Guided by these findings, we identify an amphiphilic TAM bearing a single cholesterol group and polar carboxyl functionalities as a highly promising candidate for DNP applications in membrane biology, combining efficient polarization transfer, bilayer integration, and aqueous accessibility. Full article

We investigated quantum chemical parameters for single-molecule magnets using theoretical calculations using the density functional theory (DFT), which includes the Hubbard component (PBE+U). An investigation is conducted into the transition metal phthalocyanine molecules TM-Pc (3d transition metal with TM = Ti, Cr, Mn, Co, and Cu). The energy of the frontier molecular orbitals, gap (HOMO-LUMO), electronegativity, chemical potential, global hardness, softness, and electrophilicity index are among the electronic characteristics and reactivity indices associated with TM-Pc molecules that are displayed. These characteristics are intended to help comprehend and predict the future course of innovative experimental research. As a result, the suggested materials exhibit promising properties for spintronic applications. Full article

Single-molecule detection (SMD) has reformed analytical science by enabling the direct observation of individual molecular events, thus overcoming the limitations of ensemble-averaged measurements. This review presents a comprehensive analysis of the principles, devices, and emerging materials that have shaped the current landscape of SMD. We explore a wide range of sensing mechanisms, including surface plasmon resonance, mechanochemical transduction, transistor-based sensing, optical microfiber platforms, fluorescence-based techniques, Raman scattering, and recognition tunneling, which offer distinct advantages in terms of label-free operation, ultrasensitivity, and real-time responsiveness. Each technique is critically examined through representative case studies, revealing how innovations in device architecture and signal amplification strategies have collectively pushed the detection limits into the femtomolar to attomolar range. Beyond the sensing principles, this review highlights the transformative role of advanced nanomaterials such as graphene, carbon nanotubes, quantum dots, MnO₂ nanosheets, upconversion nanocrystals, and magnetic nanoparticles. These materials enable new transduction pathways and augment the signal strength, specificity, and integration into compact and wearable biosensing platforms. We also detail the multifaceted applications of SMD across biomedical diagnostics, environmental monitoring, food safety, neuroscience, materials science, and quantum technologies, underscoring its relevance to global health, safety, and sustainability. Despite significant progress, the field faces several critical challenges, including signal reproducibility, biocompatibility, fabrication scalability, and data interpretation complexity. To address these barriers, we propose future research directions involving multimodal transduction, AI-assisted signal analytics, surface passivation techniques, and modular system design for field-deployable diagnostics. By providing a cross-disciplinary synthesis of device physics, materials science, and real-world applications, this review offers a comprehensive roadmap for the next generation of SMD technologies, poised to impact both fundamental research and translational healthcare. Full article

Pyridinecarbonitriles (pyCN), also referred to as cyanopyridines, are promising ligands for the formation of pyridine-based coordination compounds due to their two different N-donor atoms, which enable versatile coordination modes. Copper(II) complexes containing pyCN derivatives are of particular interest for their potential applications in medicinal chemistry and materials science. In this study, the synthesis, structural characterization, and thermal and magnetic properties of three new copper(II) complexes with 3-pyCN, 4-pyCN, and ethyl picolinimidate, obtained in situ by means of alcoholysis of 2-pyCN, are reported: [Cu₂(μ-Ac)₄(3-pyCN)₂] (1), [Cu(H₂O)₂(Etpic)₂]NO₃ (2), and [Cu(NO₃)₂(CH₃CN)(4-pyCN)₂]·CH₃CN (3). Single-crystal X-ray diffraction confirmed that complex 1 features a dinuclear paddle-wheel structure with bridging acetato ligands and monodentate 3-pyCN molecules, coordinated through the ring nitrogen, while complexes 2 and 3 are mononuclear. Thermal analysis showed an intense and highly exothermic decomposition of complex 3, containing nitrate ligands. Magnetic measurements revealed strong antiferromagnetic coupling in the dinuclear complex 1, whereas complexes 2 and 3 displayed paramagnetic behavior with effective magnetic moments ranging from 1.8 μ_B to 2.0 μ_B, consistent with isolated Cu(II) centers. Full article

To develop single molecule magnets, a dinuclear complex [Dy₂(HOBQ)₄Cl₆] (1) was prepared from the reaction of DyCl₃ with benzo[h]quinolin-10-ol (HOBQ). Each Dy(III) ion shows a compressed octahedral geometry and the two Dy(III) ions in 1 are bridged by two Cl⁻ ligands to construct a dinuclear structure with the four HOBQ ligands on the axial positions and six Cl⁻ ligands in the equatorial plane. Magnetic measurements showed that complex 1 is a field-induced single molecule magnet having an obvious magnetic hysteresis loop with an energy barrier of 71(2) K. These experimental results are corroborated by the ab initio complete active space self-consistent field (CASSCF) calculations which also interpret the magneto-structural correlation. It is a typical example to achieve Dy(III) SMM through regulating coordination geometry, i.e., lengthening equatorial coordination bonds and shortening axial ones to form a compressed octahedral geometry. Full article