Synthesis,characterization of Schiff base metal complexes and their biological investigation

A new Schiff base ligand named (E)‐2‐(((3‐aminophenyl)imino)methyl)phenol (HL) was prepared through condensation reaction of m‐phenylenediamine and 2‐hydroxybenzaldehyde in 1:1 molar ratio. The new ligand was characterized by elemental analysis and spectral techniques. The coordination behavior of a series of transition metal ions named Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) with the newly prepared Schiff base ligand (HL) is reported. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV–Vis, ¹H NMR, mass, electronic spectra, magnetic susceptibility and conductivity measurements and further their thermal stability was confirmed by thermogravimetric analysis (TG). From IR spectra, it was observed that the ligand is a neutral tridentate ligand coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH₂ group. The existence, the number and the position of the water molecules was studied by thermal analysis. The molecular structures of the Schiff base ligand (HL) and its metal complexes were optimized theoretically and the quantum chemical parameters were calculated. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species (Staphylococcus aureus and Bacillis subtilis, (gram positive bacteria)), (Salmonella SP., Escherichia coli and Pseudomonas aeruginosa, (gram negative bacteria)) and fungi (Aspergillus fumigatus and Candida albicans). The complexes were found to possess high biological activities against different organisms. Molecular docking was used to predict the efficiency of binding between Schiff base ligand (HL) and both receptors of Escherichia coli (3 T88) and Staphylococcus aureus (3Q8U). The receptor of Escherichia coli (3 T88) showed best interaction with Schiff base ligand (HL) compared to receptor of Staphylococcus aureu (3Q8U).     

Unveiling the Intrinsic Catalytic Activities of Single‐Gold‐Nanoparticle‐Based Enzyme Mimetics

Gold nanoparticles (AuNPs) have been demonstrated to serve as effective nanomaterial‐based enzyme mimetics (nanozymes) for a number of enzymatic reactions under mild conditions. The intrinsic glucose oxidase and peroxidase activities of single AuNPs and Ag–Au nanohybrids, respectively, were investigated by single NP collision electrochemical measurements. A significantly high turnover number of nanozymes was obtained from individual catalytic events compared with the results from the classical, ensemble‐averaged measurements. The unusual enhancement of catalytic activity of single nanozymes is believed to originate from the high accessible surface area of monodispersed NPs and the high activities of carbon‐supported NPs during single‐particle collision at a carbon ultramicroelectrode. This work introduces a new method for the precise characterization of the intrinsic catalytic activities of nanozymes, giving further insights to the design of high‐efficiency nanomaterial catalysts.     

Biosynthesis of Pd/MnO2 nanocomposite using Solanum melongena plant extract and its application for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides

In this work, for the first time, Solanum melongena plant extract was used for the green synthesis of Pd/MnO₂ nanocomposite via reduction osf Pd(II) ions to Pd(0) and their immobilization on the surface of manganese dioxide (MnO₂) nanoparticles (NPs) as an effective support. The synthesized nanocomposite were characterized by various analytical techniques such as Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDS) and UV–Vis spectroscopy. The catalytic activity of Pd/MnO₂ nanocomposite was used as a heterogeneous catalyst for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides containing various electron‐donating or electron‐withdrawing groups in the presence of K ₄ [Fe (CN) ₆ ] as non‐toxic cyanide source and sodium azide. The products were obtained in good yields via a simple methodology and easy work‐up. The nanocatalyst can be recycled and reused several times with no remarkable loss of activity.     

Synthesis,characterization and cytotoxicity of new 2‐isonicotinoyl‐N‐phenylhydrazine‐1‐carbothioamide and its metal complexes

The reaction of the newly synthesized ligand, 2‐isonicotinoyl‐N‐phenylhydrazine‐1‐carbothioamide (H₃L), with acetate salt of Co (II), Cu (II),Ni (II) and Zn (II) led to isolation of four solid complexes. The ligand and complexes structure elucidation were based on elemental analyses, spectral analyses (IR, UV–Visible, ¹H and¹³C‐NMR, MS and ESR), TGA, molar conductivity and magnetic moments measurements. The results indicated that the ligand exists in the thioketo form, while on coordination to the metal ions; it behaves as mono‐negative bidentate chelate and exists in enol form. The optical band gap measurements of the ligand and its metal complexes are in the range 3.83–4.48 eV indicating their semi‐conducting character. The cytotoxicity examination of H₃L and its Zn (II) complex showed that the ligand have very strong cytotoxicity against both HCT‐116 and HEPG‐2 cell lines while, Zn (II) complex has moderate activity.     

Essential oil composition of the aerial parts of fresh and air-dried Salvia palaestina Benth. (Lamiaceae) growing wild in Jordan

The composition of the essential oil of fresh and air-dried Salvia palaestina Benth. (Lamiaceae) growing wild in Jordan has been studied using gas chromatography-mass spectrometry analysis. The essential oils of fresh and air-dried S. palaestina were mainly composed of sesquiterpene hydrocarbons (52.66% and 65.98%, respectively). The major component detected in the oils of fresh and dry S. palaestina was germacrene D (21.18% and 26.02%, respectively). Air drying resulted in a general increase of sesquiterpene hydrocarbons and a great decrease in the percentage of monoterpene hydrocarbons.     

High-efficiency ozone generation via electrochemical oxidation of water using Ti anode coated with Ni–Sb–SnO<Subscript>2</Subscript>

Ozone (O₃) has been generated on Ni–Sb–SnO₂/Ti electrode as anode immersed in acidic media at 25 °C by electrochemical process. The anode was electrochemically characterized by cyclic voltammetry and morphologically characterized by scanning electron microscopy (SEM) and X-ray diffraction. The concentration of dissolved ozone was determined by a UV/Vis spectrophotometer. The type of electrode with different times coating on the titanium mesh and different acid type and various concentrations (C _acid) were used, and the stability of the electrode was investigated under the experimental conditions by SEM images. Results shows that higher efficiency (53.7%) for O₃ generation by electrochemical oxidation of water were obtained in HClO₄ (1 M) and an applied potential of 2.4 V vs. Ag/AgCl in 150 ml volume undivided electrochemical cell.     

A Simple Synthesis of Stable Phosphorus Ylides from Indole and Some of Its Derivatives

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of strong NH acids, such as indole and 2-methyl indole, 3-methyl indole, and 5-boromo indole. These stable ylides exist in a solution as a mixture of two geometrical isomers as a result of the restricted rotation around the carbon–carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group.     

Bioguided isolation of pentacyclic triterpenes from the leaves of Alstonia scholaris (Linn.) R. Br. growing in Egypt

Ethanolic and aqueous extracts of the leaves and flowers of Alstonia scholaris were evaluated for their antioxidant activity by investigating their effect on blood glutathione levels in alloxan-induced diabetic rats. The ethanolic extract of the leaves was the most active; therefore, its cytotoxicity against HepG2 cells was also tested. Promising GI?? values of 1.96, 4.34 and 4.65?μg?mL?1 were observed for the extract, its chloroform and ethyl acetate fractions, respectively. The chloroform active subfraction I (GI???=?2.97?μg?mL?1) yielded betulin (1), betulinic acid (2) and ursolic acid (3) upon purification. Compounds 1-3 were identified using spectroscopic techniques and by comparison with reported data. GLC of unsaponifiable and saponifiable fractions of the hexane extract revealed β-sitosterol (7.37%) and n-tetracosane (54.4%) to be the major sterol and hydrocarbon components, respectively. Linoleic acid (48.89%) was the predominant fatty acid.     

Using light and a molecular switch to 'lock' and 'unlock' the Diels-Alder reaction

Light is used to 'gate' the Diels-Alder reaction using a photoresponsive dithienylfuran backbone and turn the reversibility of the Diels-Alder reaction 'off' and 'on' at 100 °C. These features make the reported system an excellent candidate for developing the next generation of self-healing polymers and photothermal drug delivery vehicles.