Search Results (1,219)

Context/Objective: Fungi of the genus Tolypocladium are known for their diverse metabolic capabilities and medicinal potential. Indole diterpenoids (IDTs) represent a structurally unique class of fungal metabolites. Beyond their established roles as mycotoxins, these compounds have recently shown promise for neuroprotective effects. The objective of this study was to isolate and characterize novel IDTs from Tolypocladium album DWS131 and evaluate their neuroprotective activities and underlying mechanisms. Methods: IDTs were isolated through comprehensive chromatographic techniques. Their structures were elucidated using HRESIMS data, 1D/2D NMR spectra, and quantum chemical calculations. Neuroprotective effects were evaluated using glutamate (Glu)-induced R28 cells in vitro and N-methyl-D-aspartic acid-induced mouse models in vivo. A total of 48 mice were utilized for in vivo evaluations, divided into two separate experimental cohorts. In each cohort, mice were randomly assigned to four groups (n = 6 per group). Post-intravitreal injection, retinal survival and visual function were assessed via Brn3a-stained flat-mounts, H&E staining, f-VEP, f-ERG, and OptoDrum. Mechanisms involving the SLC7A11/GPX4/ACSL4 axis were investigated by Western blotting and immunofluorescence. Results: Seven previously undescribed paxilline-type IDTs, tolypindoles A–G (1–7), and two known analogues (8–9) were identified. Compounds 8 and 9 exhibited significant neuroprotection closely associated with the attenuation of oxidative stress and the modulation of ferroptosis-related pathways in Glu-induced R28 cells. In vivo, they preserved retinal ganglion cells, maintained retinal structure, and protected visual function, with compound 8 demonstrating superior efficacy. Mechanistic investigations revealed that both compounds modulate the SLC7A11/GPX4/ACSL4 signaling axis. Conclusions: This study expands the chemical diversity of T. album DWS131. Compounds 8 and 9, characterized by isopentenyl moieties, highlight a promising therapeutic potential for retinal neurodegenerative diseases such as glaucoma. Full article

Direct current (DC) surface flashover on polystyrene (PS) remains a critical bottleneck that impedes its reliable application in high-voltage insulation apparatus. To circumvent the protracted processing durations and stringent film-forming conditions inherent in conventional surface modification techniques, this study proposes a novel “liquid-film-assisted in situ rapid plasma curing” strategy. By harnessing atmospheric-pressure dielectric barrier discharge (DBD) technology within an argon ambient, the rapid (<6 min) and efficient deposition of a fluorosilane (FAS-13) functional coating onto the substrate was achieved. Microscopic characterizations coupled with isothermal surface potential decay (SPD) measurements reveal that this coating substantially mitigates the detrapping and surface migration of charge carriers. Macroscopic DC flashover testing corroborates that, under the optimal modification ratio, the surface breakdown voltage of PS is elevated to 14.04 kV, yielding an insulation gain of 26.94%. To elucidate the underlying physical mechanisms, density functional theory (DFT) calculations were conducted, revealing that the energy band misalignment between the wide-bandgap fluorinated layer and the substrate facilitates the construction of a high-density deep trap network (with a depth of ~0.8 eV) at the coating–substrate interface. By robustly anchoring primary electrons and inducing the formation of a homopolar space charge shielding layer, these deep traps physically arrest the evolution of the secondary electron emission avalanche (SEEA). Consequently, this work not only establishes a viable engineering framework for the rapid, large-scale surface reinforcement of DC insulation equipment but also provides profound quantum chemical insights into interfacial trap regulation within all-organic dielectrics. Full article

The corrosion of carbon steel in marine–industrial atmospheric environments remains a significant challenge due to the combined effect of aggressive ions such as chlorides and sulfates. In this context, this study aims to explore the inhibitory action of expired omeprazole applied to mild steel AISI 1018 evaluated on a solution simulating atmospheric corrosion (0.1 M Na₂SO₄ + 3% wt NaCl) over 72 h. The material was characterized using EDS to determine its composition of AISI 1018 steel, while Raman spectroscopy was employed to identify the functional groups and heteroatoms present on the molecular structure of omeprazole. Electrochemical noise (EN) measurements were used to evaluate the corrosion rate, type of corrosion and mechanism. Also, quantum chemical calculations of density function theory (DFT) were performed to predict the relationship between molecular structure and inhibition efficiency. The results indicate that 50 ppm provides the most stable and effective corrosion inhibition over time, as evidenced by increases in noise resistance and inhibition efficiency. In contrast, 75 ppm exhibits improved surface morphology at the end of the exposure period, which indicates enhanced surface coverage. The DFT results reveal that omeprazole possesses suitable electronic properties for corrosion inhibition, including moderate reactivity, electron-donating ability, and favorable charge distribution that promotes adsorption onto the metal surface. SEM analysis corroborates that surface damage is significantly reduced in the presence of the inhibitor, particularly at 75 ppm. This study provides new insights into the use of expired pharmaceutical compounds as corrosion inhibitors and demonstrates the capability of combining electrochemical noise analysis with DFT to evaluate both inhibition efficiency and film stability. Full article

The vibronic spectra of the first excited singlet state (S₁) and the cation spectra of the ground state of the cation (D₀) of jet-cooled cyclopropylbenzene (CPB) were investigated using resonance-enhanced multiphoton ionization (REMPI) and photoelectron velocity-map imaging techniques, respectively. The vibronic spectra indicated the existence of only the bisected conformer, a finding corroborated by quantum chemical calculations. The S₀ → S₁ electronic transition originated at 36,858.5 cm⁻¹, with an adiabatic ionization energy of 66,846 ± 15 cm⁻¹. Vibrational levels in both states were assigned with the assistance of theoretical geometry optimization and frequency calculations. These experimental spectra and theoretical calculations provided valuable insights into the structural and vibrational characteristics of CPB in its excited and cationic states. Full article

The crystal structures of monoclinic paracetamol, its cocrystal with oxalic acid (ParaOA), and its HCl monohydrate salt (ParaHCl) were refined by density functional theory (DFT) calculations and contrasted with the initial X-ray diffraction (XRD) structures. Two independent, but largely consistent, assessments were made: (i) comparisons between ¹H and ¹³C chemical shifts obtained from magic-angle spinning (MAS) nuclear magnetic resonance (NMR) experiments and those predicted by plane-wave DFT calculations before and after geometry optimization; (ii) direct ¹H–¹H distance evaluations by a recently introduced NMR crystallography method that offers straightforward structure assessments due to interatomic-distance constraints from one double-quantum–single-quantum (2Q–1Q) ¹H NMR correlation experiment. For both the ¹H/¹³C chemical shift and ¹H–¹H distance assessments, the geometry-optimized ParaHCl structure offered a markedly better match than the initial XRD structure, while the XRD structure of paracetamol revealed excellent agreement with the NMR data, with only marginal improvements offered by the DFT optimization. The XRD-derived structure of ParaOA also agreed well with the NMR chemical shift/distance constraints: While the computed ¹³C chemical shifts showed better agreement with those from MAS NMR, slightly larger discrepancies were observed for the ¹H chemical shifts and the ¹H–¹H distances. We also discuss the chemical shifts and present the first ¹H and ¹³C MAS NMR-peak assignments for the ParaHCl and ParaOA structures. Full article

Chagas disease remains a major neglected parasitic illness in Latin America and other endemic regions, and benznidazole (BZN) is still the primary trypanosomacidal drug despite its incompletely understood mechanism of action. This work provides a detailed biophysical characterization of the conformational behavior and vibrational properties of benznidazole (BZN), a first-line trypanocidal drug still widely used for the treatment of Chagas disease. Using density functional theory combined with relaxed potential energy surface scans in vacuum and implicit water, two low-energy conformers (BZN1 and BZN2) were identified, separated by moderate rotational barriers and a small energy difference, indicating that both are intrinsically accessible at room temperature. For each conformer, infrared and Raman spectra were calculated and assigned via vibrational mode analysis, then compared with FT-IR and FT-Raman spectra recorded for pharmaceutical-grade polycrystalline BZN. The theoretical and experimental spectra show excellent agreement, with a Raman band in the 1350–1400 $\mathrm{c}{\mathrm{m}}^{-1}$ region emerging as a sensitive conformational marker: the experimental maximum at $1359\mathrm{c}{\mathrm{m}}^{-1}$ matches the most intense BZN1 mode, whereas the corresponding BZN2 band appears about $13\mathrm{c}{\mathrm{m}}^{-1}$ higher in frequency. This clear spectroscopic fingerprint demonstrates that the solid drug is overwhelmingly composed of the BZN1 conformer, despite the theoretical accessibility of BZN2. Overall, the study links the conformational landscape of benznidazole to its vibrational signatures and highlights Raman spectroscopy, supported by quantum chemical calculations, as a powerful tool for conformational and potential polymorphic control of this clinically important nitroimidazole. Full article

Rotational isomers (rotamers) of substituted aromatic molecules exhibit distinct physicochemical properties that are fundamental to understanding their reactivity and biological functions. However, resolving individual rotamers spectroscopically remains challenging due to their similar transition energies and overlapping spectral features. Herein, we report the conformer-specific identification and characterization of three stable rotamers of m-ethoxyphenol using a combination of resonance-enhanced multiphoton ionization (REMPI), hole-burning (HB) spectroscopy, and mass-analyzed threshold ionization (MATI) techniques, complemented by high-level quantum chemical calculations at the B3PW91/aug-cc-pVTZ and G4 levels of theory. The S₁ ← S₀ electronic origins of rotamers I, IV, and III were determined to be 35,966 ± 2, 36,031 ± 2, and 36,198 ± 2 cm⁻¹, respectively, while their corresponding adiabatic ionization energies (IEs) were precisely measured as 64,574 ± 5, 64,122 ± 5, and 64,994 ± 5 cm⁻¹. The vibrational spectra of both the S₁ excited state and the D₀ cationic ground state were assigned, with most active modes corresponding to in-plane benzene ring vibrations. Structural analysis reveals that the benzene ring undergoes slight expansion upon S₁ ← S₀ excitation and contraction upon D₀ ← S₁ ionization, while the overall molecular geometry remains remarkably similar across all three electronic states, a key factor underlying the excellent agreement between experimental and simulated Franck–Condon spectra. Comparison with m-methoxyphenol demonstrates that the stronger electron-donating ability of the ethoxy group leads to systematically lower excitation and ionization energies. The distinct spectroscopic fingerprints established herein provide a definitive reference for identifying specific m-ethoxyphenol rotamers in future studies of this molecule and its complexes. Full article

To elucidate the physicochemical mechanisms underlying the violent explosion triggered by nylon (PA) jet penetration into explosive reactive armor, the thermal decomposition behavior of RDX and the influence mechanism of PA on its thermal reaction were studied by reaction molecular dynamics simulation and quantum chemical calculation, which were compared with experimental research. The study reveals that the decomposition of RDX is primarily initiated through pathways such as N–NO₂ homolysis, HONO elimination, and concerted ring-opening. The addition of PA reduces the energy barrier for N–N bond homolysis and provides hydrogen atoms to initiate HONO elimination via a heterogeneous pathway with a lower energy barrier, thereby promoting the initial decomposition of RDX. The free radicals produced by the decomposition of PA and RDX participate in a synergistic reaction, efficiently yielding stable products and significantly altering the distribution of intermediate species. The introduction of PA lowers the activation energy barrier for RDX decomposition and supplies hydrocarbon fragments as fuel for the reaction, facilitating rapid decomposition and initiation. This work clarifies the dual mechanism by which PA promotes RDX detonation from the perspective of microscopic reaction kinetics, providing theoretical insights for understanding and modulating the response of explosives under complex impact conditions. Full article

In this study, the synthesis of a series of alkaloid analogs—isoxazole and isothiazole esters of 2-substituted 3-oxoindoline-4-carboxylic acid was performed. The target derivatives were obtained by the carbodiimide method. It was established that the studied esters have low cytotoxicity and are able to enhance the effect of the anticancer drug carboplatin, taken in low doses (0.5–5 μM), by up to 30%. Quantum chemical modeling of the obtained compounds and their conjugates with carboplatin was carried out to analyze the relationship between various calculated parameters and the observed biological effects. Full article

This paper presents the electrochemical behavior of stainless steel 304 (SS304), a material often utilized in the wine industry, in the presence of varying concentrations of ascorbic acid (AcAS), introduced in a neutral solution (Na₂SO₄ 0.25 M + 12% (v/v) EtOH). The experimental part of this paper included potentiodynamic polarization and chronoamperometry techniques to evaluate the influence of ascorbic acid on the corrosion processes in the test solutions. Electrochemical impedance spectroscopy (EIS) has been used to investigate the charge transfer at the interface and the formation of a protective film in the absence and presence of AcAS. The Tafel method was employed to determine the kinetic parameters of the corrosion process studied. Additionally, several models of adsorption isotherms were applied to describe the interactions between AcAS and the stainless steel surface, with the Freundlich and Dubinin–Radushkevich isotherms demonstrating the most robust correlation, based on the R² correlation coefficients. Quantum chemical calculations (DFT) were also performed to clarify the molecular mechanism via which AcAS functions as an eco-friendly corrosion inhibitor in winemaking-related environments. Full article

To address the difficulty of efficiently removing calcium impurities from the manganese sulfate stripping solution obtained during the recycling of spent lithium batteries, this work proposed a binary synergistic extraction system. Quantum chemical calculations were used to screen the optimal combination (2A + 2B). The binding energy indicated the molecules combined with calcium are relatively more stable. Experimental optimization determined the optimal conditions as follows: 50 vol% of A, 25 vol% of B, saponification rate 60%, phase ratio (O/A) 2.5:1, and pH 6.0. In continuous extraction tank experiments, the calcium concentration decreased from 681 mg/L to 5 mg/L after a seven-stage counter-current extraction, with an extraction efficiency of about 99.3%. Infrared spectroscopy confirmed that the P=O double bond was the key functional group. This study provides an efficient and feasible technological pathway for the preparation of battery-grade manganese sulfate. Full article

Although amine-based post-combustion carbon capture is among the most established routes for CO₂ capture, it suffers from the high energy demand associated with amine regeneration. Recent research proposals suggest that microwave or frequency-tuned infrared heating may lead to more efficient amine regeneration processes. However, such approaches inherently introduce oscillating electromagnetic fields whose non-thermal effects on reaction pathways and energetics remain poorly understood. In this series paper, we employ high-accuracy quantum computational chemistry calculations to quantify the non-thermal effects of external electric fields on CO₂ absorption and desorption in monoethanolamine (MEA) and triethanolamine (TEA) under both aqueous and non-aqueous conditions. In this first part, we focus on static electric fields in order to establish a mechanistic reference framework helpful for interpreting non-thermal effects arising from frequency-tuned infrared laser excitation, which are addressed in Part II of this series. Our results show that static electric fields stabilize CO₂–amine reaction products, lowering absorption barriers, while consistently increasing both activation energies and reaction enthalpies associated with the amine regeneration process. This effect is particularly pronounced for MEA, where carbamate species become progressively more resistant to conversion to zwitterion as the field strength increases. These findings demonstrate that non-thermal static electric field effects counter the fundamental requirement for low-energy amine regeneration. By defining this intrinsic mechanistic limitation, the present study provides a useful baseline for assessing infrared laser-assisted carbon capture and underscores the importance of carefully selecting excitation frequencies to avoid adverse non-thermal stabilization effects. Full article

The efficient capture of chlorinated volatile organic compounds (Cl-VOCs) represents a significant challenge in environmental protection and sustainable chemical engineering. In this study, a functional deep eutectic solvent (DES) composed of tetrabutylphosphonium bromide ([P₄₄₄₄][Br]) and levulinic acid (LEV) at a 1:2 molar ratio was prepared, and its absorption performance toward two typical Cl-VOCs, namely dichloromethane (DCM) and chloroform (TCM), was evaluated using this DES as a recyclable absorbent. Based on COSMO-SAC model predictions and experimental validation, the [P₄₄₄₄][Br]-LEV (1:2) system was identified as the preferred candidate. Under mild conditions (10 °C, N₂ flow rate of 100 mL/min), the saturated absorption capacities of this DES reached 1521.71 mg/g and 1620.30 mg/g for DCM and TCM, respectively. The absorbent exhibited favorable regeneration stability over five consecutive absorption–desorption cycles, retaining over 90% of its initial absorption efficiency. Mechanistic studies, including proton nuclear magnetic resonance (¹H NMR), Fourier-transform infrared spectroscopy (FT-IR), DSC (Differential Scanning Calorimetry), TGA (Thermogravimetric Analysis) and quantum chemical calculations, including electrostatic potential (ESP), independent gradient model (IGM), and reduced density gradient (RDG), demonstrated that the absorption process was dominated by physical interactions such as hydrogen bonding and van der Waals forces, with no chemical reactions involved. At the laboratory scale, this DES system showed excellent Cl-VOCs absorption performance, providing a useful reference for the rational design of high-efficiency VOC absorbents. Full article

Aryl halides are important intermediates for chemical synthesis. However, the negative reduction potential up to −2.7 V (vs. SCE) makes photoredox conversion of aryl halides by reductive dehalogenation to aryl radicals for chemical transformations difficult. Inspired by the outstanding photophysical properties of deazaflavin and triphenylamine, as well as results of theoretical calculations, we attached the diphenylamino group to C8 of deazaflavin, and the resulting compounds look fabricated by “fusing” deazaflavin and triphenylamine (TPA) together by sharing the benzene ring. We also introduced alkyl and aryl moieties to C5 and afforded a series of deazaflavin derivatives (dFLs), namely 10-butyl-8-(diphenylamino)-3,5-dimethylpyrimido[4,5b]quinoline-2,4(3H,10H)-dione (TPAdFlMe), 10-butyl-8-(diphenylamino)-3-methyl-5-(trifluoromethyl)pyrimido[4,5-b]quinoline-2,4(3H,10H)-dione(TPAdFlTF) and 10-butyl-8-(diphenylamino)-3-methyl-5-phenylpyrimido[4,5-b]quinoline-2,4(3H,10H)-dione (TPAdFlPh), and investigated their photophysical properties and performance as sensitizers in the photodehalogenation of aryl halides. We showed that the photophysical properties are significantly improved in these dFLs. The absorption bands of dFLs are redshifted and the absorbance is more than double that of riboflavin tetraacetate (RFTA). The singlet oxygen quantum yields of TPAdFlMe, TPAdFlTF and TPAdFlPh are 0.42, 0.25 and 0.39, respectively, and the corresponding redox potentials are −1.75, −0.75 and −1.71 V vs. Ag/Ag⁺, respectively, comparable to known deazaflavin-based sensitizers. Originating from these properties, TPAdFlMe and TPAdFlPh are capable of sensitizing the full photodehalogenation of 0.038 mmol p-iodoanisole, and the yields of the photodehalogenation of 0.038 mmol p-bromoanisole are 67 and 69%, respectively. They also demonstrate exceptional performance in the photodehalogenation of halides of polycyclic aromatics with yields in the range of 73% for 1-benzhydryl-3-bromobenzene to 100% for 1-bromonapthalene in 18 h runs. The performance of TPAdFlMe and TPAdFlPh in photodehalogenation are already comparable to recently reported deazaflavin-based sensitizers, and we propose the transformation would proceed though the consecutive photo-induced electron transfer (conPET) mechanism with consecutive excitation of charged deazaflavin-based radicals under light irradiation as the key step to generating the aryl radicals, and the vital role of sensitizer-based radicals is further confirmed by mechanistic investigations. We expect the findings will help to design novel flavin-based triplet sensitizers for photoredox catalytic organic transformations. Full article

A zinc complex of chelidonic acid (4-oxo-4H-pyran-2,6-dicarboxylic acid) was obtained by reaction with zinc oxide under isothermal conditions. Its composition was confirmed by elemental and thermogravimetric analyses, and its molecular structure was characterized using NMR and IR spectroscopy. Single-crystal X-ray diffraction revealed that the complex crystallizes as a one-dimensional coordination polymer, [ZnChel(H₂O)₄]_n, in the triclinic space group P-1, featuring a distorted octahedral Zn(II) center coordinated by two chelidonate ligands and four water molecules. This six-coordinate arrangement contrasts with previously described tetra-coordinated Zn–chelidonate complexes. Quantum-chemical calculations and molecular dynamics simulations indicated that, in aqueous solution, Zn(II) preferentially forms a monodentate ZnChel(H₂O)₅ species, consistent with the solid-state coordination environment. The interaction of the complex with bovine serum albumin (BSA) was examined by fluorescence, UV–Vis absorption, and circular dichroism spectroscopy, revealing a mixed static–dynamic quenching mechanism, moderate binding affinity, and hydrogen-bonding/van der Waals contributions accompanied by alterations in BSA secondary structure. These results expand the structural chemistry of chelidonic acid and provide biophysical insight into the protein-binding behavior of zinc chelidonate, supporting its potential relevance as a zinc-based bioactive compound. Full article