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A new nonionic surfactant (NIS), namely, 17-hydroxy-3,6,9,12,15-pentaoxaheptadecyl-5- ((4-(((17-hydroxy-3,6,9,12,15-penta oxa hepta decyl) oxy) sulfonyl) phenyl) diazenyl)-2-(2-oxo-2H- chromene-3-carboxamido) benzene sulfonate was synthesized based on condensation reaction between an azo dye and polyethylene glycol. The chemical structure was elucidated from IR and 1H NMR spectral data and surface activity was measured. The inhibitive effect of the resultant NIS toward corrosion of steel in 1.0 M HCl was evaluated by potentiodynamic polarization, impedance spectroscopy (EIS), non-electrochemical methods (weight loss), surface morphology (SEM and EDX) and DFT calculations. The anti-corrosion performance showed an optimal efficiency of 96.04% at the concentration of 7.50 × 10−4 M from polarization measurements. Both the anodic and cathodic inhibition were acquired from Tafel plots polarizations (TFP). The adsorption of NIS onto steel surface obeyed Langmuir isotherm. In addition, SEM images showed higher surface protection in presence of inhibitor in agreement with a molecular dynamic simulation which exhibited optimal surface alignment between inhibitor and steel. A good agreement between electrochemical methods and DFT calculations was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel benzimidazole derivatives of three amino acids were prepared to prevent corrosion of steel. • Measurements of polarization and impedance were used to figure out how well metal was protected against corrosion. • The chemical structure was linked to the inhibitory efficiency using FMO and NBO calculations. • The average efficiencies of corrosion inhibition are outstanding, with values of 90.09%, 92.53%, and 93.43%. • The surface properties of steel were examined using the utilization of SEM-EDs measurements. Three benzimidazole derivatives, with tryptophan (BIT), tyrosine (BIY), and histidine (BIH) amino acid units, have remarkable protective properties as eco-friendly corrosion inhibitors for steel under severe acidic conditions. At a temperature of 303 K, the corrosion inhibition efficiency of BIT, BIY, and BIH at a concentration of 10 mM is 90.09 %, 92.53 %, and 93.43 %, respectively. Electrochemical tests indicate that the adsorption of these substances on the substrate leads to an increase in charge transfer resistance and interfacial electric double layer thickness. This effectively hinders the dissolution of metal and the evolution of hydrogen. The analysis of the surface structure and appearance using SEM-EDS indicates that the inhibitors have the ability to create a protective coating through both chemical and physical bonding, effectively protecting the metal from corrosive substances. Theoretical calculations, such as Density Functional Theory (DFT) and Natural Bond Orbital (NBO) analysis, along with FUKUI analysis, help identify active sites and adsorption configuration. This enhances our understanding of the corrosion mitigation mechanism. These findings align with the experimental conclusion that the formation of a stable protective film contributes to superior inhibition performance against acidic corrosion conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three novel cyano coumarin compound were synthesized and approved by FTIR, 1H NMR and Mass spectroscopy. • The synthesized inhibitors obeyed Langmuir adsorption mode with a chemical adsorption. • The metal was protected by the creation of a protective layer on the surface, according to SEM, EDX, and UV data. • The corrosion related to SRB can be controlled by the current organic coumarin inhibitors. New synthesized coumarin-buta-1, 3-diene conjugated dyes having donor–acceptor structure were prepared. The characterization of the synthesized dyes was approved by using IR, 1H NMR and Mass fragmentation analysis. The adsorption properties for the synthesized coumarin compounds were determined by experimental and theoretical methods. The corrosion inhibition effect of the synthesized coumarin dyes against steel in acid environment was investigated by plasma atomic emission spectrometer, weight loss and electrochemical methods. The highest corrosion efficiency was 97.62 % resulted from potentiodynamic polarization technique at the highest concentration for Dye 2 inhibitor. The adsorption mechanism of the inhibitors was investigated and thermodynamic parameters were calculated. The surface protection examination was carried out using scanning electron microscopy and the formation of the complex on the surface was approved using Energy dispersive X-ray spectroscopy and UV– visible spectroscopy. The quantum chemical calculations were used to confirm the donor–acceptor system of the synthesized coumarin compounds. The biological activity effect versus sulfate reducing bacteria was confirmed. The experimental and theoretical results assure that these current synthesized dyes have a good ability to protect the steel from corrosion by forming a protective layer on the surface. [ABSTRACT FROM AUTHOR]

In this work, three triazole Schiff base derivatives 1-((1H-1,2,4-triazol-3-ylimino)methyl)naphthalen-2-ol (TMN), N-(furan-2-ylmethylene)-1H-1,2,4-triazol-3-amine (FTA) and N-(thiophen-2-ylmethylene)-1H-1,2,4-triazol-3-amine (TTA) were synthesized under ultrasonic irradiation and were investigated as corrosion inhibitors. FT-IR, NMR, and elemental analysis were used to elucidate the chemical structure of the synthesized inhibitors. The inhibitive characteristics of these inhibitors on C-steel corrosion in 1.0 M HCl were studied using three different techniques. The applied techniques were Electrochemical frequency modulation, electrochemical impedance spectroscopy, and potentiodynamic polarization curves. The acquired data from the experimental methods showed that the optimal concentration for TMN, FTA, and TTA is 1.0 × 10−3 mol/L, and the inhibition efficiency reached up to 91.68%, 88.44%, and 87.29% for TMN, TTA, and FTA, respectively. Experiments also indicated that these compounds act as mixed-type inhibitors, and their concentration affects the inhibition efficiency in a directly proportional manner. Quantum paraments obtained from density functional theory (DFT) showed good agreement between experimental and computational results. [ABSTRACT FROM AUTHOR]

• Raman, Infrared and NMR spectra were interpreted based on keto-thione tautomer of 6-Methyl-2-thiouracil molecule. • Polarization and impedance measurements were analyzed for corrosion inhibition efficiency of mild steel in HCl. • FMO and NBO calculations were to correlate the active sites with the inhibition efficiency. • Adsorption annealing simulations locate the best adhering geometry of the inhibitor to the metal surface. Raman (3500-100 cm−1) and FT-ATR (4000-360 cm−1) spectra of solid 6-Methyl-2-thiouracil (6M2TU) have been recorded in addition to 1H and 13C NMR along with Mass fragmentation patterns. Moreover, the hydroxy-thiole, keto-thiole, hydroxy-thione and keto-thione tautomer's stability were theoretically probed using (DFT) B3LYP/6-31G(d,p) calculations in favor of keto-thione in the gaseous phase by ~12-24.5 kcal/mol. Moreover, the monomer and dimer structures were verified by MS/MS spectral measurements owing to the recorded m/z peaks at 141.2 and 281.1, respectively. The inhibition efficiency of 6M2TU towards mild steel iron (MSFe) against 1.0 M HCl has been investigated with molar concentrations of 0.75-7.5 × 10−3 at 30±2°C using potentiodynamic polarization, impedance measurements and electrochemical frequency modulation. The entitled compound shows a superior inhibition capability against corrosion ranged from 72-94% was obtained. The polarization curves suggest a mixed-type inhibitor for 6M2TU obeying the Langmuir adsorption model while the impedance data ensures an increase in the charge transfer resistance upon its adsorption on the surface of FeMS. Natural bond orbital (NBOs) showed an effective charge transfer from the inhibitor to d -orbitals of the metal in the following order; LP (S) > LP (O) > LP (N 1) > π (C=S) > LP (N 3) > π (C 5 =C 6) > π (C=O). The calculated low Δ E g a p (4.21 eV) predicts that 6M2TU have an efficient inhibition efficiency. Finally, The kinetic parameter F number (5.369673 cm−1) and the potential function (V 3) was estimated at 454±19 cm−1 (1.30±1.05 kcal/mol) implementing B3LYP/6-31G(d,p) optimized SPs and the calculated torsion frequency at 133 cm−1. [Display omitted] Raman, infrared and NMR spectra were used to study the molecular conformational/tautomeric structures of 6-Methyl-2-thiouracil. Vibrational interpretations were suggested for keto-thione tautomer based on normal coordinate analysis. The corrosion its inhibition effect on iron mild steel in HCl was investigated using potentiodynamic polarization and electrochemical impedance measurements favors a dominant/minor chemical/physical adsorption mechanism. [ABSTRACT FROM AUTHOR]

• Synthesis of a newly coumarin ligand and its complexes with Sm(III) and Eu(III) metal ions. • Photophysical and Luminescence results of Sm(III) and Eu(III) complexes exhibit strong red emissions. • Molecular Docking study observes the inhibition activity of coumarin compound toward xanthine oxidase enzyme. • DFT calculations show the optimized structure and separation energies of the coumarin compound. Herein, [M(HL) 2 (H 2 O) 2 NO 3 ·2H 2 O (M = Sm (III) /or Eu (III); HL = 4-(2-hydroxy benzylidene acetohyrazide)-7-hydroxy coumarin) were synthesized and characterized using several spectroscopic methods. The complexes stoichiometry with molar ratio 2L:1M were confirmed by Job's method. Tridentate ligand (HL) was coordinated to the lanthanide ions Sm(III) or Eu(III) through azomethine nitrogen atom, phenolic oxygen of hydrazide, and ketonic oxygen of the amide group. The photophysical properties of the ligand and its complexes were studied in different organic solvents and their fluorescence quantum yields were determined as well. Strong fluorescence emissions to red shifts of europium complex were observed at 580, 593, 617, 653, 693, 704 nm which were attributed to Eu(III) emission of 5D 0 →7F 0 , 5D 0 →7F 1 , 5D 0 →7F 2 , 5D 0 →7F 3, 5D 0 →7F 4, and 5D 0 →7F 5 , respectively. First-principles DFT calculations were performed to evaluate the optimized structure and separation energies of the HL compound, using the B3LYP/6-311++g(d,p) basis set. Molecular docking studies were carried out to predict the binding modes between the HL compound and active site of the xanthine oxidase enzyme [EC# (1.17.3.2) PDB ID: 1FIQ] which produced from liver patients of hepatitis C. The observed activity of the HL gave rise to the conclusion that it might exert its action through inhibition of the xanthine oxidase enzyme. [ABSTRACT FROM AUTHOR]