60 research outputs found
Ionic Liquids under Confinement: From Systematic Variations of the Ion and Pore Sizes toward an Understanding of the Structure and Dynamics in Complex Porous Carbons
We use molecular simulations of an ionic liquid in contact with a range of nanoporous carbons to investigate correlations between the ion size, pore size, pore topology, and properties of the adsorbed ions. We show that diffusion coefficients increase with the anion size and, surprisingly, with the quantity of adsorbed ions. Both findings are interpreted in terms of confinement: when the in-pore population increases, additional ions are located in less-confined sites and diffuse faster. Simulations in which the pores are enlarged while keeping the topology constant support these observations. The interpretation of properties across structures is more challenging. An interesting point is that smaller pores do not necessarily lead to a larger confinement. In this work, the highest degrees of confinement are observed for intermediate pore sizes. We also show a correlation between the quantity of adsorbed ions and the ratio between the maximum pore diameter and the pore limiting diamete
Adsorption and corrosion inhibition accomplishment for thiosemicarbazone derivatives for mild steel in 1.0 M HCl medium: Electrochemical, XPS and DFT studies
Four benzaldehyde thiosemicarbazone derivatives namely as 2-benzylidene-N-phenylhydrazinecarbothioamide
(L1), 2-(4-hydroxybenzylidene)-N-phenylhydrazinecarbothioamide (L2), 2-(4-chlorobenzylidene)-Nphenylhydrazinecarbothioamide
(L3), and 2-(4-methylbenzylidene)-N-phenylhydrazinecarbothioamide
(L4) were successfully synthesized and elucidated by physical and spectral techniques, to be specific,melting
point, elemental analysis (CHNS), infrared spectroscopy (FTIR) and 1H and 13C nuclear magnetic resonance
spectroscopy (NMR). These organic corrosion inhibitors behaviour for mild steel (MS) in 1.0 M HCl solution was
examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques.
Fromthe electrochemical measurements, most ligands behave as efficient inhibitors for theMS in 1.0MHCl solution
which contribute the maximum inhibition efficiency up to 93.38% for L3. The potentiodynamic polarization
measurements unfolds each synthesized compoundweremixed-type inhibitor based on the shifting of corrosion
potentials (Ecorr) found to be lesser than±85 mV. The electrochemical impedance spectroscopy (EIS) analysis revealed
retardation of metal corrosion succeeded by cause of adsorption of the four thiosemicarbazone derivatives
inhibitor molecules at the metal/solution interface. The adsorption of thiosemicarbazone molecules on the low
carbon steel surface in 1.0 M HCl solution obeys Langmuir adsorption isotherm. Scanning electron microscopy
(SEM) and atomic force microscopy (AFM) demonstrates in the presence of optimum concentration of L1-L4
inhibitors at 0.04mMindicates greatly reduced surface roughness ofMS in comparisonwith uninhibited solution.
The findingswere further reinforced via surface elemental analysis ofmetal/solution interface viaX-ray Photoelectron
Spectroscopy (XPS), which unveils L3 exhibit the greatest inhibition efficiency. The most plausible reason is
due to benzene rings in the molecular structure increases the adsorption ability in supporting the substituent of
chloro as well as conjugated double bond of C=N and C=S that chemisorbed along the surface of metal. The
oxide species of FeO, Fe2O3 and FeOOH found to be chemisorbed and physisorbed on MS surface. The impact of
molecular properties on the corrosion inhibition and the adsorbed sites of L1-L4 on the metal were investigated
using density functional theory calculations (DFT) at the B3LYP/6–311+G (d,p) level of theory. Fromthe Frontier
Molecular Orbitals (FMO), the Highest OccupiedMolecular Orbitals (HOMO) discloses adsorption of L2 on theMS
surface generally due to 2-(4-hydroxybenzylidene)-N-hydrazinecarbothioamide, whereas for L1, L3 and L4 associated
to the inclusion of phenyl carbothioamide. The Lowest Occupied Molecular Orbitals (LUMOs) of L1-L4 are
comparatively resembling and delocalized of all molecules. DFT reveals protonated thiosemicarbazones exhibits
high correlations coefficients as up to 99–100% in comparison to the corresponding neutral forms of themolecules.
The increase in the inhibition efficiency of protonated L1, L2 and L3 is proportional to the ΔN and DM
On the development of an original mesoscopic model to predict the capacitive properties of carbon-carbon supercapacitors
We report on the development of a lattice model to predict structural, dynamical and capacitive properties of electrochemical double layer capacitors. The model uses input from molecular simulations, such as free energy profiles to describe the ion adsorption, and experiments, such as energy barriers for transitions between lattice sites. The model developed is approximately 10,000 times faster than common molecular simulations. We apply this model to a set of carbon structures with well-defined pore sizes and investigate the solvation effect by doing simulations with neat ionic liquids as well as acetonitrile-based electrolytes. We show that our model is able to predict quantities of adsorbed ions and capacitances in a range compatible with experimental values. We show that there is a strong dependency of the calculated properties on the pore size and on the presence or absence of solvent. In particular, for neat ionic liquids, larger capacitances are obtained for smaller pores, while the opposite trend is observed for organic electrolytes
Novel 3-chloro-6-nitro-1H-indazole derivatives as promising antileishmanial candidates: synthesis, biological activity, and molecular modelling studies
An efficient pathway was disclosed for the synthesis of 3-chloro-6-nitro-1H-indazole derivatives by 1,3-dipolar cycloaddition on dipolarophile compounds 2 and 3. Faced the problem of separation of two regioisomers, a click chemistry method has allowed us to obtain regioisomers of triazole-1,4 with good yields from 82 to 90% were employed. Also, the antileishmanial biological potency of the compounds was achieved using an MTT assay that reported compound 13 as a promising growth inhibitor of Leishmania major. Molecular docking demonstrated highly stable binding with the Leishmania trypanothione reductase enzyme and produced a network of hydrophobic and hydrophilic interactions. Molecular dynamics simulations were performed for TryR-13 complex to understand its structural and intermolecular affinity stability in a biological environment. The studied complex remained in good equilibrium with a structure deviation of ∼1–3 Å. MM/GBSA binding free energies illustrated the high stability of TryR-13 complex. The studied compounds are promising leads for structural optimisation to enhance the antileishmanial activity
A Quantum Chemical and Statistical Study of Phenolic Schiff Bases with Antioxidant Activity against DPPH Free Radical
Phenolic Schiff bases are known as powerful antioxidants. To select the electronic, 2D and 3D descriptors responsible for the free radical scavenging ability of a series of 30 phenolic Schiff bases, a set of molecular descriptors were calculated by using B3P86 (Becke’s three parameter hybrid functional with Perdew 86 correlation functional) combined with 6-31 + G(d,p) basis set (i.e., at the B3P86/6-31 + G(d,p) level of theory). The chemometric methods, simple and multiple linear regressions (SLR and MLR), principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed to reduce the dimensionality and to investigate the relationship between the calculated descriptors and the antioxidant activity. The results showed that the antioxidant activity mainly depends on the first and second bond dissociation enthalpies of phenolic hydroxyl groups, the dipole moment and the hydrophobicity descriptors. The antioxidant activity is inversely proportional to the main descriptors. The selected descriptors discriminate the Schiff bases into active and inactive antioxidants
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