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The corrosion inhibition effect of di[(4-phenylimino)-4-diethyl salicylaldehyde] ether (L1) and di[(4-phenylimino)-2,6-diacetyl pyridine] ether (L2) as Schiff bases on carbon steel X48 in 1 M HCl were examined with gravimetric measurement, Tafel polarization and electrochemical impedance spectroscopy (EIS). It was observed that the two compounds L1 and L2 act as greatly corrosion inhibitors. The potentiodynamic polarization results indicate that they act as anodic and cathodic type. The adsorption of each inhibitor on the mild steel surface obeys Langmuir isotherm. The associated activation parameters together with the thermodynamic data are evaluated and discussed. The characterization of the adsorbed molecules (L1 and L2) formed on the metal surface was carried out by SEM and AFM. The improvement in corrosion resistance was related to the presence of different substituent groups, apparently due to the easiness of the electron acceptance as confirmed by the quantum chemical calculations. Additionally, the molecular dynamic simulations were used to clarify the inhibition mechanism, especially, the adsorption modes and configurations of the studied inhibitor molecules. [ABSTRACT FROM AUTHOR]

{(1Z)-2-oxo-N′-phenyl-N-quinolin-8-ylpropanehydrazonamide (H2L-H) and (1Z)-N′-(4-bromophenyl)-2-oxo-N-quinolin-8-ylpropanehydrazonamide (H2L-Br)} have been studied as corrosion inhibitors of carbon steel in 1 M HCl medium by the weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy EIS, scanning electron microscopy SEM coupled with Energy Dispersion X-Ray Spectroscopy EDS, Atomic Force Microscopy AFM, IR and UV-visible spectroscopy. The inhibition efficacy has been shown to increase with increasing inhibitor concentration. The corrosion of the carbon steel is mainly controlled by a charge transfer process. The temperature effect was evidenced and the thermodynamic parameters were calculated. The adsorption of the inhibitors on the metal surface obeyed the Langmuir adsorption isotherm. The hydrodynamic effect and the synergetic effect have been implemented. Inhibitory efficiency decreases with increasing rotation speed and the used additives adsorb cooperatively to form a protective layer on the metal surface. The results obtained by the experimental measurements and those of the theoretical calculations (DFT and MD simulation) are in good correlation. Equilibrium adsorption configurations of H2L-Br on Fe (1 1 0) surface obtained by molecular dynamic simulations [ABSTRACT FROM AUTHOR]

The inhibition effect of a new Schiff base, namely, 4,4′-thio bis{N-[ (E ) -phenol-3-ylmethylidene]aniline}(SB), on the corrosion of mild steel (MS) in a 1M HCl solution was investigated under both hydrodynamic flow and a stagnant environment at different temperatures and concentrations. To assess the inhibition effect, different characterization techniques have been used including the measurement of weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was found that the inhibition efficiency increases with the increase of the inhibitor concentration and decreases when the temperature increases. The adsorption of the inhibitor on the surface of MS obeys the Langmuir isotherm. The surfaces of MS, after being exposed to test solutions, were examined by atomic force microscopy (AFM). [ABSTRACT FROM AUTHOR]

The study of the corrosion inhibition of mild steel in acid medium 1 M HCl by the Schiff base compounds named {4,4′-Bis(pyrrole-2-carboxaldehyde) diphenyl diimino sulfide (L1) and 4,4′-Bis(thiophene-2-carboxaldehyde) diphenyl diimino sulfide (L2)} was carried out using various techniques: weight loss measurements, polarization curves, electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The influence of the concentration, immersion time and temperature was examined and the mode of adsorption of these inhibitors on the surface of the metal was highlighted by assigning the appropriate isotherm. The experimental results indicate that these compounds are effective corrosion inhibitors and the inhibitory competence rises with increasing inhibitor concentration. The adsorption of these compounds on the mild steel surface obeys the isotherm of Langmuir. The correlation between the molecular structures and the inhibitory properties of the compounds studied was performed using the Density Functional Theory (DFT) method. Furthermore, molecular dynamics (MD) simulation has been taken into account. The results indicate that the adsorption energy of L1 was less than L2, which is in accordance with the experimentally determined inhibition effect. [ABSTRACT FROM AUTHOR]

This work studies the influence of temperature (25–55 °C) and hydrodynamic conditions (0–2000 rpm) on corrosion inhibition of a azomethine compounds: PhN N C (COCH 3 ) = NC 6 H 4 Y {Y = OCH 3 (SB 1 ), CH 3 (SB 2 ), H (SB 3 ), Br (SB 4 ) and Y = Cl (SB 5 )} on mild steel in a 1 M HCl. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were employed. The results of electrochemical measurements show that the inhibition efficiency increased with increasing compound concentration and decreasing with temperature and hydrodynamic condition. The adsorption process on mild steel surface obeyed Langmuir isotherm. The associated activation parameters and thermodynamic data of adsorption were evaluated and discussed. The inhibition mechanism was determined by potential of zero charge (PZC) measurements. Corrosion attack morphologies were observed at stagnant and hydrodynamic conditions to verify qualitatively the results obtained by electrochemical methods. [ABSTRACT FROM AUTHOR]

In this paper, we report first, the synthesis and characterisation of three Schiff bases derived from histamine by condensation of histamine with various aldehydes. Then, we present a detailed DFT study based on B3LYP/6-31G(d,p) of geometrical structures and electronic properties of these compounds. The study was extended to the HOMO-LUMO analysis to calculate the energy gap (Δ), Ionisation potential (I), Electron Affinity (A), Global Hardness (η), Chemical Potential (μ), Electrophilicity (ω), Electronegativity (χ) and Polarisability (α). The calculated HOMO and LUMO energy reveals that the charge transfers occurring within the molecule. On the basis of vibration analyses, the thermodynamic properties of the titles compound were also calculated. [ABSTRACT FROM AUTHOR]

• New Schiff base and its corresponding α-aminophosphonate acid have been synthesised. • Antioxidant activities have been evaluated using the DPPH radical scavenging method. • A computentional DFT study of the antioxidant activity has been carried out. • Comparative experimental and computentional studies have been performed. • Global reactivity and Fukui indices have been calculated. A Schiff base (I1) and its corresponding α-aminophosphonic acid (P1) were synthesized using a simple and rapid preparation method and with a chemical yield of up to 75% and 68%, respectively. The structures of I1 and P1 were experimentally characterized by IR, 1H NMR, 13C NMR and 31P NMR spectroscopic methods. A test of their antioxidant activities was carried out and indicated that I1 and P1 were able to scavenge the DPPH radical. The main objective of this research was the theoretical study of the antioxidant power of I1 and P1. Density functional theory (DFT) calculations at the B3LYP/6-311+G(d, p) level were performed to determine BDE, PA, ETE, IP, PDE, spin density distribution parameters and HOMO-LUMO energies in order to study the antioxidant potential of the title products in the gas phase. According to the theoretical results, the abstraction of H atoms from the 2-OH and 1-OH groups of I1 and P1 compounds, respectively, is most preferable during the free radical scavenging process. In addition, it was shown that HAT is the thermodynamically dominant mechanism compared to SPLET and SET-PT. The calculated data of the antioxidant activity of I1 and P1 are consistent with the experimental results. A study of the chemical reactivity of these molecules was carried out. Calculations of the global parameters (chemical potential (μ), hardness (η), softness (S) and electrophilicity index (ω)) and Fukui indices of the studied compounds were done and discussed. These molecules have an electrophilic character. The Fukui functions were calculated to specify the interaction sites of these products. [Display omitted] [ABSTRACT FROM AUTHOR]

Three new Schiff-bases compounds ( I-III ) were synthesized by a condensation reaction in 1:2 M ratios of 4,4′-diaminodiphenyl sulfide and pyrrol/thiophene/furan-2-carboxaldehyde in ethanol. The structural determinations of the Schiff-bases were identified with the help of elemental analysis then confirmed by UV–Vis, FT-IR and 1 H NMR. The products were obtained in excellent yields. On the other hand, the in vitro antibacterial and antifungal activities of the synthesized compounds were investigated using disc diffusion method. Schiff bases synthesized individually exhibited varying degrees of inhibitory effects on the growth of the tested microbial species. [ABSTRACT FROM AUTHOR]

A new Schiff base namely 1,13-bis-[(2-hydroxynaphtaldehyde) 4,7,10-trioxatridecane diimine] (HNTTD) was synthesized and its corrosion behavior in 1 M hydrochloric acid solution on mild steel (MS) X48 was studied by using weight loss, polarization curves, electrochemical impedance spectroscopy (EIS) and quantum chemical calculations. All measurements showed that, inhibition efficiency increases with increasing inhibitor concentration. Polarization curves indicate that the studied compound was acting as mixed type inhibitor. The adsorption of HNTTD on steel surface followed Langmuir’s adsorption isotherm. The molecular structure effect on the corrosion inhibition efficiency was investigated by using DFT calculations. The structural and electronic parameters were calculated and discussed. The results of AFM studies further confirmed the inhibition action of HNTTD. [ABSTRACT FROM AUTHOR]

The adsorption and inhibition effect of azomethine compounds: PhN = NAC (COCH 3 ) = NC 6 H 4 Y {Y = OCH 3 (SB 1 ), CH 3 (SB 2 ), H (SB 3 ), Br (SB 4 ) and Y = Cl (SB 5 )} on mild steel in 1 M HCl at 25 °C were studied using gravimetric measurements, cyclic voltammetry, UV–visible Spectrophotométrique and scanning electron microscope (SEM) methods. Inhibition efficiency was found to increase with the increase in azomethine SB 1 -SB 5 concentration. The adsorption of each inhibitor on mild steel surface obeys Langmuir adsorption isotherm. The results of cyclic voltammetry showed that the presence of azomethine compound decreases the charge density in the transpassive region. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a (SB 1 -SB 5 )-Fe complex. SEM and EDX observations confirmed the existence of protective inhibitor film on a metal surface. [ABSTRACT FROM AUTHOR]

The corrosion inhibition effect of new azomethine compounds: PhN N C (COCH 3 ) NC 6 H 4 Y {Y = OCH 3 (SB 1 ), CH 3 (SB 2 ), H (SB 3 ), Br (SB 4 ) and Y = Cl (SB 5 )} on mild steel in 1 M HCl, was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemistry analysis. It has been found that the inhibition efficiency increased with increasing inhibitor concentration. The polarization curves showed that these Schiff bases function as mixed inhibitors. The adsorption of studied compounds on mild steel surface was found to follow the Langmuir isotherm. Molecular modeling was used to correlate corrosion inhibition properties and calculated quantum chemical parameters. [ABSTRACT FROM AUTHOR]

Highlights: [•] The new synthesized Schiff base L is efficient inhibitor in HCl and H2SO4. [•] Inhibition efficiency of L increases with increasing the L concentration. [•] The Schiff base L acts by physical and chemical adsorption on mild steel X52. [•] The adsorption behavior of L obeys Langmuir adsorption isotherm. [Copyright &y& Elsevier]

Abstract: The crystal structure of a new Schiff base: 1,2-di[4-(2-imino 4-oxo pentane)phenyl]ethane (H2L) is described. This molecule undergoes tautomerism with three tautomers: keto-imine, enol-imine and keto-amine. It acts mainly as a tetradentate ligand. Its complexes with cobalt(II), nickel(II), copper(II) are characterised using spectroscopic determinations and cyclic voltammetry. These new complex species are formulated as [CoL]·(H2O)3, [(NiCl2)2(H2L)], [CuCl2(H2L)] and [CdCl2(H2L)], respectively. The coordination occurs through the N2O2 system, using various tautomers. [Copyright &y& Elsevier]