Antibacterial and anticorrosion behavior of bioactive complexes of selected transition metal ions with new 2‐acetylpyridine Schiff base

Zinc(II) Iminopyridine Complexes as Antibacterial Agents: A Structure-to-Activity Study

Antibiotic resistance is currently a global health emergency. Metallodrugs, especially metal coordination complexes, comprise a broad variety of candidates to combat antibacterial infections. In this work, we designed a new family of Schiff base zinc(II) complexes with iminopyridine as an organic ligand and different inorganic ligands: chloride, nitrate, and acetate. The antibacterial effect of the Zn(II) complexes was studied against planktonic bacterial cells of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) strains. The results showed a moderate biocide activity in both types of planktonic bacteria, which arises from the metal complexation to the Schiff base ligand. Importantly, we confirmed the crucial effect of the metal, with Zn(II) improving the activity of Cu(II) counterparts previously reported. On the other hand, the impact of the inorganic ligands was not significant for the antibacterial effect but was relevant for the complex solubility. Finally, as proof of concept of topical antibacterial formulation, we formulated an emulsion containing the most lipophilic Zn(II) complex and confirmed a sustained release for 24 h in a vertical cell diffusion assay. The promising activity of iminopyridine Zn(II) complexes is potentially worth exploring in more detailed studies.

Green Synthesis of a Novel Cationic Surfactant Based on an Azo Schiff Compound for Use as a Carbon Steel Anticorrosion Agent

The new cationic surfactant-based azo Schiff compound (azoS8) was prepared, characterized, and investigated as a corrosion inhibitor for carbon steel in 1 M HCl by means of electrochemical approaches in this study. The chemical structure of azoS8 has been verified by the FTIR and 1H NMR spectra. According to the electrochemical system, the examined surfactant is a mixed-type inhibitor. The surfactant azoS8 was an adequate corrosion inhibitor, as evidenced by the reduction in corrosion current densities and the rise in coverage of the surface identified with an evolving inhibitor amount. When the surfactant azoS8 had been added, the capacitive cycle loops on the Nyquist plots were broader, and the dimension of these loops expanded with surfactant azoS8 concentration. This implies that the amount of surfactant azoS8 led to an improvement in the impedance of the steel electrode. The surfactant azoS8 adsorption system is well suited to the Langmuir adsorption isotherm. It was discovered that azoS8 had a Gibbs free energy change value of -27.72 kJ mol-1, which is a mixed adsorption mechanism containing both physisorption and chemisorption.

Frontiers and advances in N-heterocycle compounds as corrosion inhibitors in acid medium: Recent advances

The acid solution is widely used in chemical cleaning, oil well acidifying, and other fields, which also brings the problem of metal corrosion that cannot be underestimated. However, adding an inhibitor is one of the most convenient and effective ways to slow down metal corrosion. N-heterocyclic compounds with high stability and durability, in line with the strategy of sustainable development, have been widely studied in an acidic environment. Imidazole, pyridine, and quinoline compounds, as the most commonly used corrosion inhibitors, can form a compact protective film via π electron cloud shifting towards the N atoms to generate coordination function. In particular, flexible modifiability makes N-heterocyclic compounds adapt to different corrosion environments readily, conducive to the formation of chemical bonds between compounds with metal surfaces to be better adsorption, so as to avoid the blemish of traditional inhibitors (such as inorganic salt and organic amines inhibitors) due to excessive usage, surface roughness of metal or environmental factor (for instance, temperature, pH and metallic) causing loose bonding between film and metal surface. More importantly, the efficient corrosion inhibition and toxicity of N-heterocyclic compounds have close to do with their own functional groups. Combined with the latest research achievement, the effects of different substituents on the corrosion inhibition and corrosion inhibition mechanisms were systematically reviewed in the acid-corrosive solution of imidazole, pyridine, and quinoline and their derivatives in this review article, respectively. In addition, the application and function of density functional theory in predicting the corrosion inhibition effect of corrosion inhibitors are also discussed. The future development trend was prospected according to the summarized research results.

Anticorrosion Agents for Carbon Steel in Acidic Environments: Synthesis and Quantum Chemical Analysis of New Schiff Base Compounds with Benzylidene

Novel Schiff bases (SBs), namely, N1,N2-bis(2-(((E)-4-chlorobenzylidene)amino)ethyl)ethane-1,2-diamine (I), N1,N2-bis(2-(((E)-4-(dimethylamino)benzylidene)amino)ethyl)ethane-1,2-diamine (II), and N1,N'1-(ethane-1,2-diyl)bis(N2-((((Z)-4-dimethylamino)benzylidene) amino)methylethane-1,2-diamine) (III), were prepared and characterized by using elemental analysis, IR, and 1H NMR spectroscopy. For assessing carbon steel in diverse settings, with and without inhibitors at varying concentrations, electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PP) techniques were employed. The results showed that the synthesized inhibitors effectively decreased the corrosion rate of carbon steel in acidic media and the inhibition efficiency reached up to 93% for compound III at a concentration of 250 ppm. In addition, all prepared compounds were successful as anticorrosion agents, and the inhibition mechanism followed chemisorption from the Langmuir isotherm. The data obtained from the theoretical analysis show that the efficiency of the prepared compounds was in the order III < II < I. Furthermore, quantum chemical calculations were performed to gain insight into the electronic structure of the compounds. The analysis of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) showed that compound III had the highest surface coverage due to its specific molecular structure and spacer. This observation agreed well with the Langmuir adsorption data.

Synthesis, characterization, DFT calculations and biological activity of new Schiff base complexes

Schiff bases ligand (HL) was produced by condensing 4-aminobenzohydrazide with N-(4-chlorophenyl)-2-(4-formylphenoxy)acetamide. Cobalt (II), nickel (II), and copper (II) acetate and ligand are reacted to form 1:1 complexes. By using electronic spectra, magnetic susceptibility measurements, infrared data from 1H NMR, and XRD studies, the ligand and its metal complexes have been characterized. According to the spectrum data, the ligand functions as a monobasic bidentate, coordinating with the nitrogen atom of azomethine (-C[bond, double bond]N-) group and the oxygen atom of carbonyl group in enol form. An octahedral structure has been proposed for Co(II), Ni(II), and Cu(II) complexes according to magnetic and electronic spectrum analysis. Using the DFT method, the computational investigations of the ligand and its metal complexes showed the bond lengths, bond angles, and quantum chemical parameters. To determine the thermal stability and mode of thermal degradation of hydrazone ligand and its complexes, thermogravimetric analysis was approved out on the samples. Two calculated method, Horowitz-Metzger and Coats-Redfern, were used to calculate the characteristics of the composites' thermal degradation mechanisms at each step, including their breakdown kinetics. The ligand and its complexes were investigated for their cytotoxicity in vitro compared to human amnion (WISH) and epitheliod carcinoma (Hela). The Ni(II) complex showed highly inhibition against (WISH) growth (IC50 = 18.28±1.8 μM) with relationship to the produced chemicals and other common medications. The interaction between the ligand and its complexes with the genetic tumor (3hb5) receptor was examined using docking experiments.

Synthesis, Spectroscopic, Structural and Molecular Docking Studies of Some New Nano-Sized Ferrocene-Based Imine Chelates as Antimicrobial and Anticancer Agents

The newly synthesized organometallic acetyl ferrocene imine ligand (HL) was obtained by the direct combination of 2-acetyl ferrocene with 2-aminothiophenol. The electronic and molecular structure of acetyl ferrocene imine ligand (HL) was refined theoretically and the chemical quantum factors were computed. Complexes of the acetyl ferrocene imine ligand with metal(II)/(III) ions (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)) were fabricated. They were inspected by thermal (DTG/TG), spectroscopic techniques (FT-IR, 1H NMR, mass, UV-Vis), molar conductivity, and CHNClM to explicate their structures. Studies using scanning electron microscope (SEM) were conducted on the free acetyl ferrocene imine ligand and its Cd(II) chelate to confirm their nano-structure. To collect an idea about the effect of metal ions on anti-pathogenic properties upon chelation, the newly synthesized acetyl ferrocene imine ligand and some of its metal chelates were tested against a variety of microorganisms, including Bacillus subtilis, Staphylococcus aureus, Salmonella typhimurium, Escherichia coli, Aspergillus fumigatus, and Candida albicans. The ligand and its metal chelate were tested for cytotoxic activity in human cancer (MCF-7 cell viability) and human melanocyte cell line HBF4. It was discovered that the Cd(II) chelate had the lowest IC50 of the three and thus had the prior activity. Molecular docking was utilized to investigate the interaction of acetyl ferrocene imine ligand (HL) with the receptors of the vascular endothelial growth factor receptor VEGFR (PDB ID: 1Y6a), human Topo IIA-bound G-segment DNA crystal structure (PDB ID: 2RGR), and Escherichia coli crystal structure (PDB ID: 3T88).