Etudes théoriques de dérivés (HqX) de la 8-hydroxyquinoléine : complexes Al(qX)3 et monocouches sur Al(111)

La 8-hydroxyquinoléine (Hq) et ses dérivés (Hq chimiquement modifiée) sont connus pour leur capacité à complexer des ions métalliques. Ils sont mis en oeuvre dans la dépollution des effluents aqueux, la conception de composants électroluminescents, et l’inhibition de la corrosion de surfaces métalliques. Les propriétés de ces molécules et des complexes formés avec des ions métalliques dépendent des modifications chimiques réalisées sur la Hq. Nous effectuons des études théoriques sur la Hq et deux de ses dérivés, la 5,7-dibromo-8-hydroxyquinoléine (HqBr) et l’acide 8 hydroxyquinoléine-5-sulfonique (HqSH), dans le cadre de la Théorie de la Fonctionnelle de la Densité et en prenant en compte les forces de dispersion (DFT-D). Dans un premier temps, nous avons déterminé les formes stables des complexes issus de l’interaction entre un cation Al3+ et les molécules Hq, HqBr et HqSH déprotonées, puis nous avons effectué des analyses topologiques (ELF et QTAIM) de la structure électronique de ces complexes. Des liaisons ionocovalentes sont formées entre les molécules et l’ion Al³. Puis, nous avons étudié l’adsorption des molécules Hq, HqBr et HqSH déshydrogénées sur une surface Al(111), dans le vide et en présence d’eau (modèle de solvant implicite). Les trois types de molécules peuvent former des couches stables compactes sur la surface Al(111). A contrario, les topologies d’adsorption d’une molécule isolée sont différentes pour la Hq, dont l’efficacité en tant qu’inhibiteur de la corrosion de l’aluminium a été démontré expérimentalement, et pour les HqBr et HqSH, qui ne démontrentaucune efficacité en tant qu’inhibiteurs de corrosion. Ces conformations différentes des molécules sur la surface Al(111) en début du processus de formation des couches organiques, pourraient jouer sur leur propriété de protection de l’aluminium contre la corrosion. Enfin, la formation de complexes directement sur la surface Al(111) a été étudiée par dynamique moléculaire ab initio afin d’explorer l’espace des conformations. De nombreuses géométries stables ont été déterminées et la formation d’un complexe sur la surface par adsorption de trois molécules déshydrogénées sur une surface Al(111) présentant un ad-atome est favorisée par rapport à la précipitation d’un complexe Alq3 préalablement formé dans le vide. Ainsi, nous présentons dans ce travail une description : i) de la nature précise des liaisons dans les complexes Alq3, ii) des géométries des dérivés de la Hq adsorbés sur une surface Al(111), iii) de la formation sur Al(111) de complexes de type Alq3 par adsorption de molécules Hq déshydrogénées sur une surface Al(111)

Molecular modeling applied to corrosion inhibition : a critical review

In the last few years, organic corrosion inhibitors have been used as a green alternative to toxic inorganic compounds to prevent corrosion in materials. Nonetheless, the fundamental mechanisms determining their inhibition performance are still far from understood. Molecular modeling can provide important insights into those mechanisms, allowing for a detailed analysis of the corrosion inhibition (CI) process. However, CI modeling is frequently underexplored and commonly used in a standardized way following a pre-determined recipe to support experimental data. We highlight six fundamental aspects (A) that one should consider when modeling CI: (A1) the electronic properties of isolated inhibitors, (A2) the interaction of the inhibitor with the surface, (A3) the surface model, (A4) the effect of the anodic and cathodic zones on the surface, (A5) the solvent effects, and (A6) the electrodes' potential effects. While A1-A3 are more frequently investigated, A4-A6 and some more complex surface models from A3 are usually not considered and represent gaps in the CI modeling literature. In this review, we discuss the main features of molecular modeling applied to CI, considering the aforementioned key aspects and focusing on the gaps that the emerging approaches aim to fill. Filling these gaps will allow performing more detailed simulations of the CI process, which, coupled with artificial intelligence (AI) methods and multiscale approaches, might construct the bridge between the nanoscale CI modeling and the continuum scale of the CI processes

Synthesis, Characterization, and Reactivity Evaluation of Late Transition Metal-Aluminum Heterobimetallic Complexes Toward Molecular Hydrogen

Synthesis, Characterization, and Reactivity Evaluation of Late Transition Metal-Aluminum Heterobimetallic Complexes Toward Molecular Hydroge

Understanding the anticorrosion properties of chitosan grafted poly-aspartic acid against mild steel corrosion in 1 M HCl: Electrochemical and theoretical considerations

The mechanism of the anticorrosion effects of chitosan grafted with poly-aspartic acid (CTS-PAA) against mild steel in 1 M HCl has been provided using combined electrochemical and theoretical approaches. The successful grafting of chitosan (CTS) with poly-aspartic acid (PAA) was verified with intensive Furrier-transformed infrared spectroscopy (FTIR).   In the studied system, a minimal corrosion inhibition efficiency of about 60 % was obtained with the unmodified CTS whereas CTS-PAA inhibition efficiency reaching a maximum number of 98.9 % at 250 ppm concentration was obtained. Polarization studies show that the inhibitors acted on both the anodic and cathodic currents curves indicating a mixed inhibition protection mechanism while the electrochemical impedance data show that the protection was afforded by interfacial adsorption of the inhibitor species on the steel surface. The adsorption process fitted to Langmuir adsorption isotherm. The proposed inhibition mechanism linked the enhanced inhibition performance of CTS-PAA to the extension of the adsorption sites by the grafting agents which was confirmed with X-ray photoelectron spectroscopy (XPS) results. The experimental data were correctly complemented with density functional theory (DFT)/molecular dynamic simulation (MDS) data and the binding energy of the modified polymer is over two magnitudes higher than the individual molecules affirming the experimental findings.

A review on biomass-derived materials and their applications as corrosion inhibitors, catalysts, food and drug delivery agents

Owing to the overconsumption of petroleum-based resources and growing demand for fossil-based fuels and chemicals, it has become imperative to adopt alternative resources that are renewable. With the availability of biomass, it is believed that this technology has the capability to valorize waste into wealth. Recently, efficient utilization of plant biomass, a chief renewable resource, has gained tremendous attention in research as it offers distinct social, economic, and sustainable benefits. The present review focuses on the various biomass from waste resources. Subsequently, the applications of these polymeric biomass composites are reviewed in catalysis, drug delivery, and food applications. Finally, corrosion studies along with DFT calculations and theoretical aspects have also been reviewed. Naturally occurring carbohydrate polymers found in lignocellulosic biomass are biopolymers have been used for various physical and chemical applications; as catalyst, coatings, drug delivery, corrosion inhibitors etc. This review reports these material applications of carbohydrate polymers. In this review, we focus on new and emerging applications of polymers from lignocellulosic biomass

Ba(H2PO3)2.0.5H2O: Synthesis, crystal structure optimization, vibrational study, DFT computation and application as a corrosion inhibitor

This investigation involved the synthesis of barium phosphite Ba(H2PO3)2.0.5H2O by reacting barium chloride with phosphorous acid. The physical characteristics, FT-IR spectra, and X-ray diffraction were employed to validate the composition of the synthesized substance, and powder X-ray diffraction (PXRD) was used to determine the phase purity. The optimal molecular geometry, infrared intensities were calculated using density functional theory (DFT/B3LYP) methods with the LanL2DZ basis set. The HOMO-LUMO properties and geometries of this compound have been determined and discussed. The computational structural parameters are generally in agreement with the experimental investigations. The theoretical infrared for the title compound has been constructed. Additionally, the anti-corrosion properties of this compound were investigated in an acidic solution using weight loss and electrochemical techniques. The results showed good effectiveness, indicating the formation of a protective film on the C38 surface

Corrosion inhibition of carbon steel in acidic solutions using Phaseolus vulgaris L. extract as a green inhibitor

The anticorrosion characteristics of Phaseolus vulgaris L. aqueous leaves extract were examined for the protection of carbon steel in 0.5 M sulfuric acid and 0.5 M phosphoric acid solutions using potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). The extract acted as mixed-type inhibitor, and was more potent in H3PO4 than in H2SO4. The adsorption of the extract on the metal surface obeyed Flory–Huggins, Temkin, and the Kinetic-Thermodynamic isotherms but not the Langmuir model. Analysis of the thermodynamic and activation parameters suggested that physical adsorption governed the inhibition mechanism. The total phenolic, total flavonoid, total carbohydrates, and protein contents in the extract were 121.80 ± 3.65 mg GAE/g DW, 67.65 ± 2.31 mg RE/g DW, 2.67 ± 0.32 mg GE/g DW, and 0.122%, respectively. The richness of the extract in phenolic compounds justified the strong adsorption of the P. vulgaris phytochemicals onto the surface of the metal

From molecules to mobilities : modelling charge transport in organic semiconductors

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