Chemical Studies Research Articles

Unconventional Radical and Radical-Hole Site-Based Interactions in Halogen-Bearing Dimers and Trimers: A Comparative Study.

Radical (R•) and R•-hole site-based interactions are comparatively studied, for the first time, using ab initio methods. In this regard, R•-bearing molecules •XO3 (where X = Cl, Br, and I) were subjected to direct interaction with NH3 within dimeric and trimeric forms in the form of NH3···•XO3/•XO3···NH3 and NH3···•XO3···NH3 complexes, respectively. As confirmed by electrostatic potential analysis, the studied R•-bearing molecules •XO3 had the outstanding potentiality to interact as Lewis acid centers via two positive sites dubbed as R• and R•-hole sites. Such an observation proposed the potentiality of the considered •XO3 molecules to engage in unconventional R• and well-established R•-hole site-based interactions with Lewis bases. This was confirmed by negative interaction (E int) energies, ranging from -4.93 to -19.89 kcal/mol, with higher favorability for R• site-based interactions over the R•-hole site-based ones. MP2 energetic features furnished higher preferability for the R• site-based interactions than the R•-hole site-based ones in the case of chlorine- and bromine-bearing complexes, and the reverse was true for the iodine-bearing complexes. Moreover, elevated E int values were recorded for the NH3···•XO3···NH3 trimers over the NH3···•XO3 and •XO3···NH3 dimers, outlining the higher preference of the •XO3 molecules to engage in R• and R•-hole site-based interactions in the trimeric form over the dimeric one. These results might be considered a requisite linchpin for numerous forthcoming supramolecular chemistry and crystal engineering studies.

Fluorine and Bromine Dual-Doped Nanoporous Carbons: Preparation and Surface Chemistry Studies.

A novel method for the concurrent introduction of fluorine and bromine into the surface of nanoporous activated carbon (NAC) is evaluated. According to the method, the preheated NAC was treated with 1,2-dibromotetrafluoroethane at elevated temperatures (400-800 °C). Potentiometric and elemental analysis, nitrogen adsorption-desorption, scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and 19F solid-state NMR were used to study the NAC microstructure and changes in surface chemistry. The specific modification temperature was found to have a decisive influence on the resulting halogen content of the NAC surface. About 1.5 mmol g-1 of bromine and only 0.5 mmol g-1 of fluorine are chemisorbed on the NAC surface when dual-doped at 400 °C. The fluorination efficiency increases dramatically to 1.84-2.22 mmol g-1 when the process temperature is increased to 500-700 °C. Under the same conditions, the bromination efficiency unexpectedly decreases to 0.66-1.32 mmol g-1. Since halogen-containing groups undergo significant thermal decomposition around 800 °C, the overall halogenation efficiency decreases, accordingly. Both the volume and surface area of the micropores decrease moderately when halogen-containing groups are introduced into the carbon surface layer. Fluorine and bromine are unevenly distributed in the porous structure of the dual-doped NACs, and the outer surface is more halogen-rich than the inner surface of the micropores. XPS and 19F solid-state NMR revealed the selective formation of CF2 groups in the NAC surface layer independent of the temperature. In contrast, the percentage of semi-ionic fluorine in the form of CF groups directly bonded to the π-electron system of the carbon matrix increases significantly with temperature.

Multi-iron subpopulations in Liller 1 from high-resolution H-band spectroscopy

We present a high-resolution chemical study of a representative sample of 21 luminous giant stars in Liller 1, a complex stellar system in the Galactic bulge, based on H-band spectra acquired with the Near-Infrared Spectrograph at KeckII. In this sample, we found fifteen stars with a subsolar iron abundance and enhanced alpha /Fe and Al/Fe likely older, having formed early and quickly from gas mainly enriched by type II supernovae, and six stars with supersolar iron and roughly solar-scaled alpha /Fe and Al/Fe likely younger, having formed at later epochs from gas also enriched by type Ia supernovae. Moreover, both subpopulations show enhanced N/Fe as in the bulge field, approximately solar-scaled V/Fe and depletion of C/Fe and 12C/13C with respect to the solar values, indicating the occurrence of significant mixing in the stellar interiors of these evolved stars. Our study also reveals that the subsolar subpopulation shows some structuring, and the presence of a third subcomponent with iron content and intermediate alpha /Fe enhancement, in between that of the metal-poor and metal-rich main subpopulations, has been statistically assessed, providing the chemical signature of both an extended star formation with multiple bursts and some self-enrichment.

Dynamics of HCN, HNC, and HNCO Formation in the 193 nm Photodissociation of Formamide.

Formamide (NH2CHO) is the simplest molecule containing a peptide linkage [-NH-C(═O)-], and it plays an essential role in the study of prebiotic chemistry. Exposure to UV irradiation allows formamide to decompose and act as a prebiotic feedstock in the formation of nucleobases and other necessary starting materials. The photodissociation mechanism of gaseous formamide at 193 nm is studied using (a) chirped-pulse Fourier transform millimeter-wave spectroscopy in the 260-290 GHz spectral region in a room-temperature flow-tube reactor at 1 μbar pressure, (b) a combination of electronic structure theory, transition state theory, and quasiclassical trajectories, and (c) the Active Thermochemical Tables. The HCN and HNC photoproducts of hydrogenated (NH2CHO) and deuterated (NH2CDO and ND2CHO) formamide precursors are examined to gain insight into the photodissociation mechanism. The theoretical investigation has characterized the main pathway leading to each of the HCN/HNC isomers from the precursor isotopologues. The theoretical branching ratio [HNC]/[HCN] = 2.1 for nascent photofragments agrees with the experiment. The effect of the postphotolysis HNC ↔ HCN isomerization on the [HNC]/[HCN] ratio is predicted. We report the experimental branching ratio [HNCO]: ([HNC] + [HCN]) = 12 ± 3 and propose that most of HNCO originates from dissociation on the S1 electronic state of formamide.

ROBERT: Bridging the Gap Between Machine Learning and Chemistry

ABSTRACTBeyond addressing technological demands, the integration of machine learning (ML) into human societies has also promoted sustainability through the adoption of digitalized protocols. Despite these advantages and the abundance of available toolkits, a substantial implementation gap is preventing the widespread incorporation of ML protocols into the computational and experimental chemistry communities. In this work, we introduce ROBERT, a software carefully crafted to make ML more accessible to chemists of all programming skill levels, while achieving results comparable to those of field experts. We conducted benchmarking using six recent ML studies in chemistry containing from 18 to 4149 entries. Furthermore, we demonstrated the program's ability to initiate workflows directly from SMILES strings, which simplifies the generation of ML predictors for common chemistry problems. To assess ROBERT's practicality in real‐life scenarios, we employed it to discover new luminescent Pd complexes with a modest dataset of 23 points, a frequently encountered scenario in experimental studies.

Stabilization of crude oil-contaminated Bushehr carbonate sand: physical and chemical study

Stabilization of crude oil-contaminated Bushehr carbonate sand: physical and chemical study

First report of poorly known genus Gloeoheppia (Ascomycota: Gloeoheppiaceae), reveals one new species from Pakistan

The new species Gloeoheppia immersusia sp. nov. is described from Darel Valley, Gilgit Baltistan, Pakistan. A comparative morpho-anatomical and chemical study and ITS-based molecular analyse indicated a position of this new species within the genus Gloeoheppia Gyeln. Gloeoheppia immersusia sp. nov. is closely related to G. turgida (Ach.) Gyeln and G. erosa (J. Steiner) Marton, characterized by thallus gelatinose, squamulose to peltate, upper surface blackish brown to dark olive brown, apothecial disc blackish brown to reddish brown, apothecia 0.4 – 1 mm, hymenium 110–150 μm, subhymenium 50–85 μm, exciple 30–42 μm, ascospores 12–18 × 6–9 μm and growing on calcareous rocks. A key and comparison to all existing species of the genus Gloeoheppia is also given.

Adducts of bovine serum albumin and binuclear nitrosyl iron complex with thiosulfate ligands: a molecular docking and quantum chemical study

Adducts of bovine serum albumin and binuclear nitrosyl iron complex with thiosulfate ligands: a molecular docking and quantum chemical study

Chemical kinetic study of methane blended with ammonia cracked gas at elevated temperature and pressure

Ammonia (NH3) on-line cracking to produce hydrogen (H2) can avoid direct ammonia combustion and is an important method to enhance combustion performance and control nitrogen oxide (NOx) emissions. This work aims to study the effects of various ammonia energy ratios (ENH3) and cracking ratios (CNH3) on the combustion and NO emission characteristics of methane (CH4) blended with ammonia cracked gas under lean-burn condition. The results showed that methane co-combustion and ammonia cracking significantly enhance the laminar burning velocity (LBV). The chemical effect plays a dominant role in the enhancement of LBV, but its relative contribution gradually decreases with increasing ENH3 and CNH3. A linear relationship between LBV and (O+H+OH+NH2 + CH3)max was observed, with both the slope and intercept being functions of CNH3. At an ENH3 of 20 %, NO emission decrease with increasing CNH3. At an ENH3 of 80 %, NO emission first increase and then decrease. The percentage of thermal NO is less than 1 % under ambient condition and could increase to as much as 22 % under elevated condition (500 K, 10 atm). Additionally, there was a quadratic polynomial relationship between (O+H+OH+NH2)max and the final NO mole fraction within an equivalence ratio range from 0.4 to 0.8. The second-order coefficient exhibits a linear correlation with CNH3, while the first-order and constant coefficient show a quadratic polynomial correlation with CNH3.

Ab initio chemical kinetics and shock-tube experimental study on nitrocyclohexane pyrolysis and combustion

Nitrocyclohexane (NCH) is a model nitroalkane compound with naphthenic structural groups for studying the combustion properties of nitro-based energetic fuels, and also demonstrates significant potential applications for advanced engines. However, accurate description of the detailed kinetic mechanisms for pyrolysis and combustion of NCH receives little attentions. Herein, the detailed pyrolysis and oxidation mechanism of NCH is studied by using quantum chemistry calculations and chemical kinetic theory. The potential energy surfaces of the CN bond dissociation reaction, HONO elimination reaction, abstraction reactions of NCH as well as the subsequent β-scission reactions are calculated using G4//M06–2X/6–311++G(d, p) method, which are subsequently employed for reaction rate constant computations via transition state theory (TST) and RRKM/master-equation (RRKM/ME) method. The ab initio chemical kinetic study results are used to develop a detailed kinetic mechanism to predict the pyrolysis experimental results of NCH, which are performed using a single-pulse shock tube (SPST). The SPST experiment is performed at pressure of 10 bar, temperature ranging from 1070 to 1560 K, reaction time of around 1.77 microsecond with fuel concentrations of 0.5 % diluted by Argon gas. The developed detailed kinetic mechanism exhibits reasonable prediction results of the pyrolysis product distributions together with literature ignition delay times across a wide range of temperature, pressure, and equivalence ratio conditions. Rate-of-production analysis is conducted to gain insight into the pyrolysis chemical kinetics of NCH. The present work should be valuable for the study of the combustion chemistry of nitro-alkane energetic fuels.

Improving high-voltage cycling and stabilizing the electrode-electrolyte interface of nickel-rich layered cathodes by magnesium doping

Next-generation lithium-ion batteries will rely on nickel-rich layered oxides as cathode materials, but these materials are associated with structural and voltage losses. Magnesium (Mg) doping helps improve the performance of the nickel-rich layered cathode material. The Mg-modified LiNi0·90Mn0·05Co0·05O2 (NMC-90) has been successfully synthesized through a co-precipitation technique followed by calcination at 850 °C. Modified NMC-90 exhibits better-organized layers and improved interfacial properties than pristine ones based on structural, chemical, and morphological studies. In a voltage range of 2.8–4.5 V, Mg (0.01 mol%)-doped NMC-90 (NMC-M1) composite cathode shows an excellent discharge capacity of 211.11 mAh/g, whereas pristine NMC-90 (NMC-M0) attains only 210.59 mAh/g at 0.1C with an initial coulombic efficiency of 89.5 % for NMC-M1 and 87.5 % for NMC-M0 cathode. The NMC-M1 cathode demonstrated an impressive enhancement in cyclability after 60 cycles compared to the NMC-M0 at 1C rate, in which the NMC-M1 cathode attains a high capacity retention of 80 % while the NMC-M0 cathode shows only 37 %. This study illustrates the importance of studying the effects of elemental doping on cell performance. It will drive the future development of cathode materials with high Ni and low Co content.

Comprehensive chemical characterization study of three major fruit residues from São Paulo State (Brazil): banana pseudostem, orange bagasse, and guava seed cake

Comprehensive chemical characterization study of three major fruit residues from São Paulo State (Brazil): banana pseudostem, orange bagasse, and guava seed cake

Single Crystal, Spectroscopic Measurement, Quantum Chemical Studies, and Antimicrobial Potency of a new Cadmium Compound as a Potential Candidate for Therapeutic Antibacterial drug Development

Single Crystal, Spectroscopic Measurement, Quantum Chemical Studies, and Antimicrobial Potency of a new Cadmium Compound as a Potential Candidate for Therapeutic Antibacterial drug Development

Comparative study of Sombor index and its various versions using regression models for top priority polycyclic aromatic hydrocarbons

The aromatic compounds having structural configurations with two or more fused benzene rings are the polycyclic aromatic hydrocarbons (PAHs). Topological indices are valuable tools for studying the structure property relationships of PAHs and also helps in predicting various properties and activities. They find applications widely in computational chemistry, drug design and QSPR studies. This article focuses on analysing the potential predictive index for Sombor index (SO), elliptic Sombor index (ESO), Euler Sombor index (EU), reverse Sombor index (RSO), reverse elliptic Sombor index (RESO) and reverse Euler Sombor index (REU) using regression models for top priority 38 PAHs. From the study it is evident that, SO and RSO have proved to be potential predictive indices among the considered degree-based and reverse degree-based indices. The variation of best predictive index with minimal RMSE are plotted for linear, quadratic and cubic regression models for better understanding.

Novel Superhard Boron Nitrides, B2N3 and B3N3: Crystal Chemistry and First-Principles Studies.

Tetragonal and hexagonal hybrid sp3/sp2 carbon allotropes C5 were proposed based on crystal chemistry and subsequently used as template structures to identify new binary phases of the B-N system, specifically tetragonal and hexagonal boron nitrides, B2N3 and B3N3. The ground structures and energy-dependent quantities of the new phases were computed within the framework of quantum density functional theory (DFT). All four new boron nitrides were found to be cohesive and mechanically (elastic constants) stable. Vickers hardness (HV), evaluated by various models, qualified all new phases as superhard (HV > 40 GPa). Dynamically, all new boron nitrides were found to be stable from positive phonon frequencies. The electronic band structures revealed mainly conductive behavior due to the presence of π electrons of sp2-like hybrid atoms.

Effect of electron-donating and -withdrawing substitutions in naphthoquinone sensitizers: The structure engineering of dyes for DSSCs in Quantum Chemical Study

Dye-sensitized solar cells (DSSCs) are cost-effective photovoltaic devices that convert solar energy into electricity using a dye sensitizer, TiO2 photoanode, electrolyte, and counter electrode. This study investigates the impact of substituents on the performance of naphthoquinone-based dye sensitizers in DSSCs. We analyzed various naphthoquinone derivatives’ electronic structures and light absorption properties using DFT and TD-DFT. Our results demonstrate that electron-donating groups enhance DSSC performance by improving light absorption and electron injection. Specifically, naphthoquinone derivatives with methoxy (Dye-2) and methyl (Dye-3) groups showed superior properties. TD-DFT analysis revealed high molar extinction coefficients over a broad spectrum, making these dyes efficient at capturing sunlight. Additionally, these dyes effectively interact with TiO2, which is crucial for photostability and photovoltaic performance. In conclusion, naphthoquinone derivatives with electron-donating groups significantly improve DSSC performance, with Dye-2 and Dye-3 being strong candidates for high-performance applications.

Parkinsonia praecox bark as a new source of antibacterial and anticancer compounds

IntroductionParkinsonia praecox is used in traditional medicine to treat various diseases; however, the antibacterial and anticancer properties from its bark have not been reported. Thus, this study aimed to evaluate the antibacterial activity, cytotoxicity and chemical study of methanolic extract of Parkinsonia praecox bark (PpBM). MethodsThe PpBM antibacterial activity was determined against pathogen strains using the broth microdilution method, the cytotoxic effect was assessed on cancerous (HepG2, SKOV-3 and HeLa) and non-cancerous (J774A.1 and HaCaT) cells using the crystal violet assay, the in vitro hemotoxicity was evaluated using the hemolysis assay on human erythrocytes and the identification of major compounds derived from PpBM was performed by 1H and 13C NMR and 2D NMR experiments. ResultsPpBM (2000 µg/mL) demonstrated antibacterial activity against Listeria monocytogenes, a potential breakthrough in the fight against this pathogen. PpBM decreased cell viability of HepG2 liver cancer cells (IC50, 104.56 µg/mL) with a selectivity index of 1.38 regarding J774A.1 macrophages and 2.04 to HaCaT keratinocytes, suggesting a selective anticancer potential. On the other hand, PpBM did not cause hemolysis to high concentrations (1000 µg/mL) or alterations in the morphology of human erythrocytes at doses lower than 200 µg/mL. For the first time, lupenone, germanicone, 3-oxo-oleanane-18-en-28-ol, and combretol were identified in P. praecox. PpBM showed antibacterial, selective anticancer, and non-hemotoxic properties. These activities may be related to the major compounds, such as lupenone. ConclusionP. praecox bark is a new option for obtaining bioactive compounds, further in vitro and in vivo studies are required to confirm their efficacy and safety.

Technological usage of ripe banana pulp for the development of a salad dressing

Oxidized banana (OB) is one of the important food wastes which contains a high potential to use in different products such as salad dressing. OB is a good ingredient in salad dressing due to its presence of antioxidants, vitamins, dietary fibers, and starch. the current study aimed to replace OB with non-oxidized banana (T1: 0 % T2: 25 %, T3: 50 %, T4: 75 %, and T5: 100 % OB) in salad dressing formulation and focused on the effects of OB on color, sensory, physical, chemical, rheological properties, microbial growth, and consumer studies. E-nose and volatile compounds analysis by GC-MS was also performed. According to the results, L*, a*, and b* values decreased significantly (P < 0.5) leading to a darker color of the product and effected other color evaluations (Hue, chroma, and ∆E). Viscosity was decreased significantly by the addition of the OB in the dressing formulation while pH did not change between T5 and T1 treatments. All sensory attributes score (9-point hedonic scale) decreased and consumers were given of fact of OB salad dressing has environmental benefits. Steady shear flow measurements, frequency sweep analysis, and the thixotropic loop of the oxidized banana indicated that adding OB to salad dressing negatively affected textural properties. The most effective attributes are, texture, and color discriminating the underlying differences among all 5 treatments according to MANOVA Wilks’ P-values. McNemar’s test was applied to analyze before and after consumers had been given the information about OB environmental benefits indicating that emotional attributes were changed after knowing the fact state as well as the odds ratio predicted purchase intent which increased with an increase in overall liking, pleased, flavor, and satisfied attributes. The acceptability threshold for OB in salad dressing formulation is 50 % OB. Among the identified volatile organic compounds are acetic acid, hexanoic acid, 3-methyl-1-butanol, 2-methylpropyl acetate, ethyl hexanoate, and phenylethyl acetate. The volatile organic compounds identified are 3-methyl-butanoic acid, 2-methyl-butanoic acid, and (E)-2-Decenal. The electronic device could discriminate these aromas, and the results obtained agree with those of the tasting panel and the volatile compounds.

Optimizing Production, Characterization, and In Vitro Behavior of Silymarin-Eudragit Electrosprayed Fiber for Anti-Inflammatory Effects: A Chemical Study.

Inflammatory Bowel Disease (IBD) is a chronic condition that affects approximately 1.6 million Americans. While current polyphenols for treating IBD can be expensive and cause unwanted side effects, there is an opportunity regarding a new drug/polymer formulation using silymarin and an electrospray procedure. Silymarin is a naturally occurring polyphenolic flavonoid antioxidant that has shown promising results as a pharmacological agent due to its antioxidant and hepatoprotective characteristics. This study aims to produce a drug-polymer complex named the SILS100-Electrofiber complex, using an electrospray system. The vertical set-up of the electrospray system was optimized at a 1:10 of silymarin and Eudragit® S100 polymer to enhance surface area and microfiber encapsulation. The SILS100-Electrofiber complex was evaluated using drug release kinetics via UV Spectrophotometry, Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Differential Scanning Calorimetry (DSC). Drug loading, apparent solubility, and antioxidant activity were also evaluated. The study was successful in creating fiber-like encapsulation of the silymarin drug with strand diameters ranging from 5-7 μm, with results showing greater silymarin release in Simulated Intestinal Fluid (SIF) compared to Simulated Gastric Fluid (SGF). Moving forward, this study aims to provide future insight into the formulation of drug-polymer complexes for IBD treatment and targeted drug release using electrospray and microencapsulation.

Zinc isoporphyrin from [Zn(4-Cl)TPP]: Synthesis, characterization, density functional theory and molecular docking studies

This study concerns the synthesis of zinc isoporphyrin (2), from zinc porphyrin [Zn(4-Cl)TPP], (1), where TPP- tetraphenylporphyrin ligand. Because of the prospective applications such as an infrared dye and catalyst in photomedicine, isoporphyrin has been in high demand. However, there is limited documentation of metalloisoporphyrins. Here, we have discussed the synthesis, characterization, coordination chemistry and theoretical studies of zinc isoporphyrin, 2. Compound 2 was characterized using UV–visible, 1H NMR, 13C NMR and ESI Mass analysis. Electrochemical studies were carried out using cyclic voltammetry. Theoretical studies including structure optimization, analysis of electronic transition, and natural bond analysis (NBO) were performed for both 1 and 2. Besides that, the global reactivity indices of 1 were compared with 2. The lower HOMO-LUMO energy gap in 2 (1.95 eV) supports the shifting of Q bands to a lower energy region. The molecular docking studies of 1 and 2 were performed for the first time and found that isoporphyrins can act as a potential inhibitor of G-quartet DNA associated with cancer disease. These results may be useful in designing effective therapeutics for the treatment of cancer.