Synthesis,characterization, and biological screening of metal complexes of novel sulfonamide derivatives: Experimental and theoretical analysis of sulfonamide crystal

This study reports the synthesis of sulfonamide-derived Schiff bases as ligands L ¹ and L ² as well as their transition metal complexes [VO(IV), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II)]. The Schiff bases (4-{E-[(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzene-1-sulfonamide ( L ¹ ) and 4-{[(2-hydroxy-3-methoxyphenyl)methylidene]amino}-N-(5-methyl-1,2-oxazol-3-yl)benzene-1-sulfonamide ( L ² ) were synthesized by the condensation reaction of 4-aminobenzene-1-sulfonamide and 4-amino-N-(3-methyl-2,3-dihydro-1,2-oxazol-5-yl)benzene-1-sulfonamide with 2-hydroxy-3-methoxybenzaldehyde in an equimolar ratio. Sulfonamide core ligands behaved as bidentate ligands and coordinated with transition metals via nitrogen of azomethine and the oxygen of the hydroxyl group. Ligand L ¹ was recovered in its crystalline form and was analyzed by single-crystal X-ray diffraction technique which held monoclinic crystal system with space group (P2₁/c). The structures of the ligands L ¹ and L ² and their transition metal complexes were established by their physical (melting point, color, yields, solubility, magnetic susceptibility, and conductance measurements), spectral (UV–visible [UV–Vis], Fourier transform infrared spectroscopy, ¹H NMR, ¹³C NMR, and mass analysis), and analytical (CHN analysis) techniques. Furthermore, computational analysis (vibrational bands, frontier molecular orbitals (FMOs), and natural bonding orbitals [NBOs]) were performed for ligands through density functional theory utilizing B3LYP/6-311+G(d,p) level and UV–Vis analysis was carried out by time-dependent density functional theory. Theoretical spectroscopic data were in line with the experimental spectroscopic data. NBO analysis confirmed the extraordinary stability of the ligands in their conjugative interactions. Global reactivity parameters computed from the FMO energies indicated the ligands were bioactive by nature. These procedures ensured the charge transfer phenomenon for the ligands and reasonable relevance was established with experimental results. The synthesized compounds were screened for antimicrobial activities against bacterial (Streptococcus aureus, Bacillus subtilis, Eshcheria coli, and Klebsiella pneomoniae) species and fungal (Aspergillus niger and Aspergillus flavous) strains. A further assay was designed for screening of their antioxidant activities (2,2-diphenyl-1-picrylhydrazine radical scavenging activity, total phenolic contents, and total iron reducing power) and enzyme inhibition properties (amylase, protease, acetylcholinesterase, and butyrylcholinesterase). The substantial results of these activities proved the ligands and their transition metal complexes to be bioactive in their nature.     

Selective aerobic photocatalytic oxidation of benzyl alcohol over spherical structured WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> nanocomposite under visible light irradiation

TiO₂/WO₃ nanocomposite with nanodisk morphology was prepared and successfully used as a photocatalyst. The nanocomposite was obtained via sonochemical and hydrothermal methods, using pomegranate juice as a capping agent. The products were characterized by FE-SEM imaging, BET, EDAX spectroscopy, X-ray diffraction, DRS, and FT-IR spectroscopy. TiO₂/WO₃ nanocomposite showed high sensitivity to absorb visible light in compared to TiO₂. In an optimized condition, the yield of the aerobic photocatalytic oxidation of benzyl alcohol derivatives reached to 65% for the TiO₂/WO₃ nanocomposite, while the conversion percent of the derivatives was less than 8% and 50% on the TiO₂ and WO₃ nanoparticles, respectively. Experimental results were supported by density functional theory (DFT) calculations. The DFT results in several solvents of different dielectric constants, confirmed the strong dependence of light absorption and photocatalytic activity to adsorption energy of the substrates on the surface of the nanoparticles (E_ad). In addition, the theoretical results showed an inverse correlation between the adsorption energy of benzyl alcohol and its conversion percent, accordance to the experimental trend.

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Integrated Transmission Electron and Single‐Molecule Fluorescence Microscopy Correlates Reactivity with Ultrastructure in a Single Catalyst Particle

Establishing structure–activity relationships in complex, hierarchically structured nanomaterials, such as fluid catalytic cracking (FCC) catalysts, requires characterization with complementary, correlated analysis techniques. An integrated setup has been developed to perform transmission electron microscopy (TEM) and single‐molecule fluorescence (SMF) microscopy on such nanostructured samples. Correlated structure–reactivity information was obtained for 100 nm thin, microtomed sections of a single FCC catalyst particle using this novel SMF‐TEM high‐resolution combination. High reactivity in a thiophene oligomerization probe reaction correlated well with TEM‐derived zeolite locations, while matrix components, such as clay and amorphous binder material, were found not to display activity. Differences in fluorescence intensity were also observed within and between distinct zeolite aggregate domains, indicating that not all zeolite domains are equally active.     

Interaction of methyl beta-D-xylopyranoside with metal ions: density functional theory study of cationic and neutral bridging and pendant complexes

Density functional theory calculations on complexes of 4C1, 1C4 and 2SO ring conformations of methyl beta-D-xylopyranoside 1 with divalent metal cations, M = Mg2+, Ca2+, Zn2+, and Cd2+, are presented. Bridging and pendant cationic, [M(H2O)41]2+ and [M(H2O)(5)1]2+, as well as neutral complexes, [M(OH)2(H2O)(2)1] and [M(OH)2(H2O)(3)1], and neutral complexes involving a doubly deprotonated sugar, [M(H2O)(4)1(2-)], are considered. In aqueous and chloroform solution the stability of cationic and pendant neutral complexes is greatly diminished compared with gas-phase results. In contrast, bridging neutral complexes [M(OH)2(H2O)(2)1] and those of type [M(H2O)(4)1(2-)], are stabilized with increasing solvent polarity. Solvation also profoundly influences the preferred binding position and ring conformation. Compared with complexes of bare metal cations, additional ligands, e.g., H2O or OH-, significantly reduce the stability of 1C4 ring complexes. Irrespective of the cation, the most stable structure of bridging complexes [M(H2O)(4)1]2+ results from coordination of the metal to O3 and O4 of methyl beta-D-xylopyranoside in its 4C1 ring conformation.     

Low thermalconductive,transparent and hydrophobic ambient pressure dried silica aerogels with various preparation conditions using sodium silicate solutions

The experimental results on the preparation of low thermal conductivity and transparent ambient pressure dried silica aerogels with the sodium silicate solution, TMCS silylating agent with methanol, isopropyl alcohol, hexane and xylene solvents, are reported. This study is focussed on the effect of preparation conditions such as varying the number of preparation steps, pH of the hydrosol and hydrogel ageing temperature, for the production of the low thermal conductive silica aerogels and the results are analysed. Density, thermal conductivity, % of optical transmission and contact angle of the aerogels were measured. The Fourier Transform Infrared Spectroscopy (FTIR) studies revealed the presence of Si–C and C–H along with the Si–O–Si and OH bonds and their intensities strongly depend on the processing steps, pH of the hydrosol and gel ageing temperature. The UV–Visible spectra indicated the % of optical transmission of the aerogels decreased with increasing the number of processing steps, increase in the pH of the hydrosol from 3 to 8 and decreased for ageing temperature up to 50 °C. Further increase in temperature >50 °C, the % of optical transmission of the aerogels increased. The TGA-DTA data showed the thermal stability of the aerogels with respect to hydrophobicity is 325 °C. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) analyses revealed the nanostructure of the aerogels. The porosity of the aerogels was studied using the pore size distribution. Silica aerogels with low density (0.051 g/cc), low thermal conductivity (0.049 W/m K), optical transmission (65%), high hydrophobicity (159°) and resistance to humid atmosphere >1 year was obtained in the present studies.     

The classification of finite groups by using iteration digraphs

A digraph is associated with a finite group by utilizing the power map f: G → G defined by f(x) = x^kfor all x ∈ G, where k is a fixed natural number. It is denoted by γG(n, k). In this paper, the generalized quaternion and 2-groups are stud- ied. The height structure is discussed for the generalized quaternion. The necessary and sufficient conditions on a power digraph of a 2-group are determined for a 2-group to be a generalized quaternion group. Further, the classification of two generated 2-groups as abelian or non-abelian in terms of semi-regularity of the power digraphs is completed.     

Hydrogen generation from weak acids: electrochemical and computational studies of a diiron hydrogenase mimic

Extended investigation of electrocatalytic generation of dihydrogen using [(mu-1,2-benzenedithiolato)][Fe(CO)3]2 has revealed that weak acids, such as acetic acid, can be used. The catalytic reduction producing dihydrogen occurs at approximately -2 V for several carboxylic acids and phenols resulting in overpotentials of only -0.44 to -0.71 V depending on the weak acid used. This unusual catalytic reduction occurs at a potential at which the starting material, in the absence of a proton source, does not show a reduction peak. The mechanism for this process and structures for the intermediates have been discerned by electrochemical and computational analysis. These studies reveal that the catalyst is the monoanion of the starting material and an ECEC mechanism occurs.     

Development of Antibacterial,Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels’ crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker–Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R² = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.     

Long-Life Lead-Carbon Batteries for Stationary Energy Storage Applications

Owing to the mature technology, natural abundance of raw materials, high recycling efficiency, cost-effectiveness, and high safety of lead-acid batteries (LABs) have received much more attention from large to medium energy storage systems for many years. Lead carbon batteries (LCBs) offer exceptional performance at the high-rate partial state of charge (HRPSoC) and higher charge acceptance than LAB, making them promising for hybrid electric vehicles and stationary energy storage applications. Despite that, adding carbon to the negative active electrode considerably enhances the electrochemical performance. However, carbon brings some adverse effects, such as the severe hydrogen evolution reaction (HER) in the NAM due to the low overpotential of carbon material, promoting severe water loss in LCBs. From a practical application point of view, the irreversible sulfation of the negative active material (NAM) and extreme shedding and softening of the positive active material (PAM) are the main obstacles for next-generation LCBs. Recently, a lead-carbon composite additive delayed the parasitic hydrogen evolution and eliminated the sulfation problem, ensuring a long life of LCBs for practical aspects. This comprehensive review outlines a brief developmental historical background of LAB, its shifting towards LCB, the failure mode of LAB, and possible potential solutions to tackle the failure problems. The detailed LCB′s development towards long life was discussed in light of the reported literature to guide the researcher to date progress. More emphasis was directed toward the new applications of LCBs for stationary energy storage applications. Finally, state-of-the-art progress and further research gaps were pointed out for future work in this exciting era.