Experimental and Computational Anticorrosion Behaviors of Pyrazole s-Triazine/anilino-morpholino Derivatives for Steel in Acidic Solutions.

The corrosion inhibition of C-steel by two s-triazine/morpholino-anilino-pyrazole derivatives, namely, 4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-morpholino-N-phenyl-1,3,5-triazin-2-amine (1) and N-(4-bromophenyl)-4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-morpholino-1,3,5-triazin-2-amine (2) was investigated by impedimetric and potentiometric studies. It was found that (1) and (2) acted as cathodic-type corrosion inhibitors that retard the hydrogen evolution reaction. The percent corrosion inhibition, 98.5% for compound (2) (with bromo substituent) at 80 ppm, was slightly higher than 97.8% for (1) at 100 ppm. Thus, the replacement of a -H with -Br substituent increased the corrosion inhibition properties. Compound (2) exhibited Temkin isotherm adsorption, whereas compound (1) exhibited Langmuir adsorption. Scanning electron microscopy (SEM) analysis of the steel surface indicated that the inhibitors caused protection of the surface. The weight loss experiment also proved the decrease in the corrosion rate when inhibitors were added. The difference in inhibitory efficiency between compounds (1) and (2) was investigated by density functional theory (DFT) to study neutral and protonated species in gaseous and aqueous phases. The theoretical analysis demonstrated that compound (2) exhibited higher inhibitory activity on a metal surface compared to compound (1), aligning with the experimental results. The energy associated with the metal/adsorbate arrangement, represented by dE ads/dNi , was higher for (2) (-380.91 kcal mol-1) compared to (1) (-371.64 kcal mol-1). This indicated better adsorption of (2) over (1).

Bis(dimethylpyrazolyl)-aniline-s-triazine derivatives as efficient corrosion inhibitors for C-steel and computational studies.

4,6-Bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-phenyl-1,3,5-triazin-2-amine (PTA-1), N-(4-bromophenyl)-4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-amine (PTA-2) and 4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(4-methoxyphenyl)-1,3,5-triazin-2-amine (PTA-3) were synthesized and characterized. Their corrosion inhibition of carbon C-steel in 0.25 M H2SO4 was studied by electrochemical impedance. The inhibition efficiency (IE%) of triazine was superior due to the cumulative inhibition of triazine core structure and pyrazole motif. Potentiodynamic polarizations suggested that s-triazine derivatives behave as mixed type inhibitors. The IE% values were 96.5% and 93.4% at 120 ppm for inhibitor PTA-2 and PTA-3 bearing -Br and -OCH3 groups on aniline, respectively. While PTA-1 without an electron donating group showed only 79.0% inhibition at 175 ppm. The adsorption of triazine derivatives followed Langmuir and Frumkin models. The values of adsorption equilibrium constant K°ads and free energy change ΔG°ads revealed that adsorption of inhibitor onto steel surface was favoured. A corrosion inhibition mechanism was proposed suggesting the presence of physical and chemical interactions. Density functional theory computational investigation corroborated nicely with the experimental results. Monte Carlo simulation revealed that the energy associated with the metal/adsorbate arrangement dE ads/dN i, for both forms of PTA-2 and PTA-3 with electron donating groups (-439.73 and -436.62 kcal mol-1) is higher than that of PTA-1 molecule (-428.73 kcal mol-1). This aligned with experimental inhibition efficiency results.

Exploring the Sensing Potential of g-C3N4 versus Li/g-C3N4 Nanoflakes toward Hazardous Organic Volatiles: A DFT Simulation Study.

Ab initio calculations were performed to determine the sensing behavior of g-C3N4 and Li metal-doped g-C3N4 (Li/g-C3N4) quantum dots toward toxic compounds acetamide (AA), benzamide (BA), and their thio-analogues, namely, thioacetamide (TAA) and thiobenzamide (TAA). For optimization and interaction energies, the ωB97XD/6-31G(d,p) level of theory was used. Interaction energies (Eint) illustrate the high thermodynamic stabilities of the designed complexes due to the presence of the noncovalent interactions. The presence of electrostatic forces in some complexes is also observed. The observed trend of Eint in g-C3N4 complexes was BA > TAA > AA > TBA, while in Li/g-C3N4, the trend was BA > AA > TBA > TAA. The electronic properties were studied by frontier molecular orbital (FMO) and natural bond orbital analyses. According to FMO, lithium metal doping greatly enhanced the conductivity of the complexes by generating new HOMOs near the Fermi level. A significant amount of charge transfer was also observed in complexes, reflecting the increase in charge conductivity. NCI and QTAIM analyses evidenced the presence of significant noncovalent dispersion and electrostatic forces in Li/g-C3N4 and respective complexes. Charge decomposition analysis gave an idea of the transfer of charge density between quantum dots and analytes. Finally, TD-DFT explained the optical behavior of the reported complexes. The findings of this study suggested that both bare g-C3N4 and Li/g-C3N4 can effectively be used as atmospheric sensors having excellent adsorbing properties toward toxic analytes.