Journal of Chemical Sciences最新文献

Solid-state anhydrous (QA) and hydrated quercetins (QH) were studied by using combustion calorimetry and thermal analysis-simultaneous thermogravimetry (TG) coupled with differential scanning calorimetry (DSC) methods. The enthalpies of formation were derived employing the experimental heat of combustion for the studied compounds. The obtained data are compared with estimated values using group additivity and quantum calculations. The correlation between experimental and calculated values is discussed considering the number and strength of intermolecular hydrogen bonds. From DSC experiments, the temperature ranges of dehydration followed by melting-decomposition were established.

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The present study consists in bringing contributions to the completion of thermochemical data banks regarding the important role played by quercetin in the living organisms. The values of the thermodynamic quantities, which characterize the biochemical reactions, are put in correspondence with the biological activity of quercetin.

Synopsis The present study consists in bringing contributions to the completion of thermochemical data banks regarding the important role played by quercetin in the living organisms. The values of the thermodynamic quantities, which characterize the biochemical reactions, are put in correspondence with the biological activity of quercetin.

The advancement of the hydrogen economy worldwide has facilitated the production of hydrogen from various resources. The water-gas shift reaction (WGSR) serves as a critical intermediate step for hydrogen enrichment and CO reduction in syngas derived from carbon-based hydrogen production. This paper presents a numerical investigation into the kinetic modelling of high-temperature WGSR using an iron-based catalyst in a reactor equipped with a Ni membrane. The study employs the Podolski et al. kinetic model with a 93% Fe₂O₃/7% Cr₂O₃ catalyst to evaluate the impact of temperature and the CO/H₂O molar ratio on the overall reaction performance. Results indicate that an increase in temperature leads to a decrease in reactant conversion. To achieve optimal CO conversion and H₂ generation, a CO/H₂O molar input ratio of 1 is necessary. On the other hand, a microkinetic model for WGSR based on the formate mechanism over an iron-based catalyst is proposed. This comprehensive model includes seven adsorbed species and encompasses 18 elementary-step forward reactions. The developed model also enables the evaluation of temperature effects on surface coverage. Key intermediates identified in the model include OH* and HCOO* species. Additionally, it was determined that CO activation is more favorable at high temperatures.

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The kinetic modelling of the high-temperature water-gas shift reaction (HT-WGSR) was explored for hydrogen production. The process utilized a hydrogen-selective Ni-dense membrane reactor combined with iron-based catalysts, aiming to enhance efficiency and optimize hydrogen separation. Various parameters, such as temperature and feed ratio, influencing reaction rates were also evaluated.

A safe method of producing pyrano[2,3-d]pyrimidine scaffolds without the need for a catalyst is shown, utilizing the concepts of green chemistry. This is achieved by employing polyfluorinated alcohol as a reusable medium and mixing barbituric acid/1,3-dimethylbarbituric acid, malononitrile and aryl aldehydes in an environmentally friendly manner. This environmentally friendly method uses one pot, readily accessible, low-cost reaction media, safe reaction conditions, no requirement for column chromatography for separation and effective use of resources. Furthermore, green 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) did not require significant modifications and remained stable for four reuses. This is highly helpful in satisfying industrial demands and resolving environmental issues.

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Our study shows that 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) is used as a reusable medium to synthesize pyrano[2,3-d]pyrimidine frameworks without the need for a catalyst. This eco-friendly, cost-effective and straightforward solution has several benefits. It employs readily accessible materials, reduces the need for costly and dangerous chemicals, saves time and yields high-quality results.

Charge transfer complexes including [HBT] and [FBT], 4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile with picric acid, and 2,4-dinitrophenol were synthesized by FTIR and 1H NMR. The full geometrical optimization, frontier molecular orbitals energies, energy gap, chemical reactivity indices, MEP maps, thermodynamic properties, the vibrational spectra, and partial density of states have been investigated at the DFT level (B3LYP) using the basis set SDD (Stuttgart/Dresden ECP plus DZ). Using the investigated computational analysis, it was concluded that the existence of H-bond beside charge transfer interaction is certainly responsible for the high stability of the formed CT complexes. The decrement of the HOMO-LUMO energy gap, a quantum chemical descriptor, explains the ease with which charge transfer interactions take place within the molecule. NBO explains the eventual hyper-conjugative interaction and charge delocalization that take place within the CT complexes and are responsible for the high optical nonlinearity of the HBT-PA, HBT-DNP, FBT-PA, and FBT-DNP complexes. NMR spectra reconfirmed the formation of the new compound, including both charge and hydrogen bonding. The nonlinear optical property and total dipole moment of the CT complexes reveal that the CT complexes could be a suitable candidate for nonlinear optical applications in optoelectronic devices.

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The synthesized charge transfer complexes (HBT-PA, HBT-DNP, FBT-PA, and FBT-DNP) were characterized by FTIR, NMR, and DFT methods (B3LYP/SDD). Geometrical optimization, HOMO-LUMO energy gap, chemical reactivity, and NBO analysis confirmed charge transfer interactions and hydrogen bonding, enhancing optical nonlinearity. These complexes are promising for optoelectronic applications.

A facile one-pot multicomponent reaction employing aromatic aldehydes, malononitrile, and phthalhydrazide in H₂O and EtOH (1:1) mixture at 80ºC has been innovated for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones. This approach stands out for its simplicity, ease of execution, and high efficiency. The reaction employs 20 mol% of imidazole as an organocatalyst, enhancing its practicality and applicability. A total of 14 compounds were synthesized within 0.5 to 4 h under a greener reaction medium, with the yields of products ranging from 85–94%. The key components of this protocol are the use of H₂O:EtOH (1:1) mixture as green solvent, recyclable reaction medium, imidazole as an organocatalyst, mild reaction conditions, easy isolation of products, good to excellent yields, and no column chromatographic purification. Using the microbial dilution method, all the synthesized compounds underwent evaluation for their antibacterial activity against a spectrum of strains, including E. coli, S. aureus, P. aeruginosa, B. subtilis, as well as antifungal activity against A. flavus and A. niger. The synthesized derivatives exhibited diverse inhibitory effects on the growth of both bacterial and fungal strains, showcasing their potential utility across various microbial targets.

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A simple one-pot multicomponent reaction using substituted aromatic aldehydes, malononitrile, and phthalhydrazide in 10 ml of H₂O and EtOH (1:1) mixture at 80ºC for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives has been developed. This methodology involves the use of greener solvents and imidazole as an organocatalyst which leads to good to excellent yields of the products with less reaction time.

This investigation involves synthesizing a new composite, blending graphene oxide (GO), HKUST-1 (copper-based metal–organic frameworks), and titanium dioxide (TiO₂) via the hydrothermal method. Following that, the prepared composite is utilized in the design of a photocatalyst and electrochemical sensing platform. Numerous analytical methods, such as XRD, FT-IR, SEM-EDX, TGA, UV-Vis investigations, and suitable electrochemical analyses, were used to examine the morphological and structural characteristics of the crafted material. The tailored composite exhibited remarkable efficiency, showcasing an exceptional degradation efficiency of 97.47% for MB dye within just an hour under sunlight irradiation. On the other hand, the electrochemical sensor developed by fabricating the surface of a glassy carbon electrode (GCE) referred to as GO@HKUST-1@TiO₂/GCE exhibited a remarkable catalytic effect on the electrochemical response to imatinib (IMB). The sensor displayed exceptional electrocatalytic performance for detecting IMB under optimized conditions, including solution pH and scan rate. Calibration plots showed linear segments within the concentration range of 2–20 µM, with a significant limit of detection (LOD). The fabricated sensor demonstrated high accuracy, reproducibility, and stability throughout various electrochemical assessments. Thus, the dual functionality of the material has been established.

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A novel composite comprising graphene oxide (GO), HKUST-1, and titanium dioxide (TiO₂) namely GO@HKUST@TiO₂ was synthesized and utilized for both photocatalytic degradation of methylene blue (MB) dye and electrochemical sensing of imatinib (IMB). The composite demonstrated exceptional efficiency in both applications, highlighting its potential for dual-functionality.

Cyanobiphenyls are well-known for their liquid crystalline organization. The molecules that can undergo self-assembly on the surface of metal, offer potent corrosion inhibition properties. Herein we report five such cyanobiphenyl derivatives as potential anti-corrosion films on the surface of mild steel immersed in 1M HCl medium. The electrochemical impedance measurements and potentiodynamic polarization measurements reveal that the cyanobiphenyl derivative with shortest chain length out of the five inhibitors under consideration (i.e., 4′-((6-mercaptohexyl)oxy)-[1,1′-biphenyl]-4-carbonitrile) exhibited up to 98% efficiency for the drop cast volume of 25 µL of 1 mg/mL of stock solution as compared to increased chain length molecules. The surface characterization of the corroded and protected mild steel surface was done by using a scanning electron microscope and energy-dispersive X-ray spectroscopic methods which affirms the presence of protective film on the surface of mild steel after exposure to acid medium. The theoretical calculations support experimental observations with respect to trends in the efficiency of short-chain and long-chain functionalized cyanobiphenyls.

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Five different chain-length cyanobiphenyls appended thiols as anti-corrosive materials on the surface of mild steel in an acidic medium were investigated by electrochemical, theoretical and surface characterization methods. The efficacy of the molecule was as high as 98–99% at a very small drop cast volume of 25 µL.

Conformational space of small molecules can be exploited to deploy the hierarchical nature of intermolecular interactions, such as hydrogen bonding and π-stacking in the crystal structures. Modulation of conformational space was achieved by varying the alkyl chain length in N′-phenylalkylsquaramates and bis-N,N′-diphenylalkylsquaramides, which were synthesized by condensation of dimethyl squarate with the corresponding phenyl alkylamines. In the crystal structures of these compounds, even though the catemeric N–H···O hydrogen bonding is the primary interaction and hierarchy in the secondary interactions consisting of π-stacking and H···H bonding leads to a large variation in molecular structures in the solid state.

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Conformational variation in the alkyl chain linker connected to central squaramide unit is contingent to the variation in partner chain length.

The emergence of aggregation-induced emission luminogens (AIEgens) has significantly stimulated the development of luminescent supramolecular materials because of their strong emissions in the aggregated state. With this inspiration, pyrene tethered Schiff base molecule, namely (Z)-1-(2,4-dinitrophenyl)-2-(pyren-1-ylmethylene), hydrazine was designed and successfully synthesized and well characterized by using proton (¹H NMR), Fourier–transform infrared (FT-IR), and electron ionization mass spectrometry (EI-MS). UV-visible absorption and emission studies have been employed to elucidate self-assembled and aggregation properties. It is shown that monomers of synthesized compounds can exhibit emission driven by assembly by forming an H-aggregate, which corresponds to its blue shift tuning to the visible region associated with the extended π-conjugation. Furthermore, to have a more profound understanding of the supramolecular assembly, TEM and confocal microscopy were utilized to verify the aggregate morphology. In both investigations, monomer aggregation into a vesicular structure with monodispersed PDI is preferred.

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Pyrene tethered Schiff base molecule, namely (Z)-1-(2,4-dinitrophenyl)-2-(pyren-1-ylmethylene), hydrazine was designed and successfully synthesized. Monomer 1 demonstrating aggregation-induced emission upon increasing the gradual amount of H₂O in DMF solution of compound 1 (DMF/H₂O, 30/70 (v/v). Pictorial representation is also pasted along with TEM and confocal results of aggregate or supramolecular structures of synthesised compound.

An acid-catalyzed three-component reaction of arylglyoxals, quinoxalin-6-amine and 4-hydroxycoumarin is described, leading to the synthesis of new functionalized 7H-pyrrolo[3,2-f]quinoxaline derivatives with good yields. It has high synthetic efficiency and operational simplicity, and only water was generated as a byproduct.

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A new procedure for the synthesis of pyrrolo[3,2-f]quinoxaline derivatives.