Journal of Physical and Theoretical Chemistry
Volume:14 Issue: 2, Summer 2018

The study examined corrosion inhibition of corrosion inhibition of 5-methyl-2H-imidazol-4-carboxaldehyde and 1H-Indole-3-carboxaldehyde on mild steel in acidic medium using weight loss and Density Functional Theory (DFT) methods. DFT calculations were carried out at B3LYP/6-31+G** level of theory in aqueous medium on the molecular structures to describe electronic parameters. The values of thermodynamic parameters such as free energy of adsorption (ΔGºads), adsorption equilibrium constant (Kads), adsorption entropy (ΔSºads), adsorption enthalpy (ΔHºads) and activation energy (Ea) were calculated, analyzed and discussed. The adsorption process on mild steel surface showed that 4-methylimidazol-5-carboxaldehyde and Indole-3-carboxaldehyde obeyed Freundlich and Temkin adsorption isotherms respectively. Also, the molecular parameters associated with inhibition efficiency such as EHOMO, ELUMO, band gap energy (ELUMO- EHOMO), softness (S), electron affinity (EA) and number of electrons transfer were calculated. The higher inhibitory property of 5-methyl-2H-imidazol-4-carboxaldehyde was attributed to the presence of higher number of protonation sites as a result of higher number of nitrogen atoms, increase in number of plane protonated species and higher net charges on the ring atoms.

In the present work, the quantum theoretical calculations of the molecular structure of the compound 2-(Cyclohexylamino)-2-oxo-1-(quinolin-4-yl)ethyl 4-Chlorobenzoate have been predicted using Density Functional Theory (DFT) in the gas phase. The geometry of the title structure was optimized by B3LYP/6-31+G* and HF/6-31+G* levels of theory. The theoretical 1H and 13C NMR chemical shift values of the title structure are calculated and compared with the experimental results. The calculated results are in good agreement with the experimental data. The theoretical vibrational frequencies values are obtained and compared with the experimental data. The electronic spectra of the title structure in the gas phase were carried out by TDB3LYP/6-31+G* and TDHF/6-31+G* levels of theory. Frontier molecular orbitals (FMOs), the molecular electrostatic potential (MEP), natural charges distribution (NBO charges), electronic properties such as ionization potential (I), electron affinity (A), global hardness (η), electronegativity (χ), electronic chemical potential (μ) and electrophilicity (ω), chemical softness (S=1/η), and NBO analysis were investigated and discussed by theoretical calculations.

M06-2X functional was employed to study halogen-π interactions in X-C2-Y…C8H8 complexes (X, Y=H, F, Cl, and Br). In fact, interactions of mono- or di-halogenated acetylenes and planar cyclooctatetraene as an anti-aromatic π system were considered. Relationship between binding energies of the complexes and charge transfer effects was investigated. Also, electronic charge density values were calculated using atoms in molecules (AIM) method to connect properties of bond, ring, and cage critical points (BCPs, RCPs, and CCPs) to binding energies of the mentioned complexes. Size of halogen atoms has a role on strength of halogen-π interactions. Decrease of electronic charge density values at BCPs and CCPs of the complexes and increase of alteration of these values at RCPs is relatively consistent with increase of binding energies. Electron-withdrawing nature of Br atom leads to inverse charge transfer in some complexes.Description of halogen-π interactions on an anti-aromatic ring help to design new molecular systems with unique properties for crystal engineering.

The characterization of an optical sensor membrane is described for the determination of Hg2+ ions based on the immobilization of 5, 6 Di methyl -1- ( 4 methyl benzyl) -2- para tolyl-1H-benzimidazole (DMBPTBI) on a triacetylcellulose membrane. The membrane responds to mercury ions by changing color reversibly from orange to red in universal buffer solution at pH 2. Under optimum conditions, the proposed membrane displayed a linear range of 0.1-12 μg mL-1 with a limit of detection of, 0.02 μg mL-1 at a wavelength of 558 nm. The response time of the optode was about 8 -10 min, depending on the concentration of mercury (II) ions. The coefficients of variation (CV) of the sensor response for, 1.0 μg mL-1 of Hg(II) was, 1.8% and the CV between seven membranes was 2.3%. The sensor can readily be regenerated with the ethylene diamine solution. The optode is fully reversible and the selectivity of optode to Hg2+ ions in universal buffer is relatively good as interferences. The proposed optode was applied successfully for the determination of mercury (II) in various samples.

In this study Bis(1,4-dinitro toprop-2-yl) Nitramine, BNA, was attached to boron nitride nano- cages (B12N12). , thermodynamic parameters of BNA with B12N12 have been computed using one of the methods of density functional theory (B3LYP) In the temperature variety 300 to 400 K each 10 degree one times, were calculated. So these materials were geometrically optimized. After that thermodynamic parameters were calculated. Enthalpy values (ΔH), Specific heat capacity (Cv) and Gibbs free energy (ΔG) were computed for these reactions. Finally, the effect of nano structures on explosion properties and other chemical attributes of BNA were evaluated.

In this 4D-QSAR study, we obtained pharmacophore identification and biological activity prediction for 50 propoxy methylphenyl oxadiazole derivatives by the Electron Conformational Genetic Algorithm approach. In light of the results given in the data obtained from quantum chemical calculations at HF/3-21 G level, the electron conformational matrices of congruity (ECMC) were built by EMRE software. Considering the pharmacophore atoms, a parameter pool was introduced into the field. To find the theoretical biological activity of the molecules used in this study, the non-linear least squares regression method and genetic algorithm were used to determine the best subset of variables affecting bioactivity. As can be understand from our explanations, it should be noted that the results obtained in this study are in good agreement with the experimental data presented in the literature. The model for the training and test sets attained by the optimum 8 parameters gave highly satisfactory results with R2training= 0.872, q2=0.836 and SEtraining=0.059, q2ext1 = 0.787, q2ext2 = 0.786, q2ext3=0.830, ccctr = 0.933, ccctest = 0.896 and cccall = 0.926.

In this paper, quantum chemical parameters at density functional theory (DFT) B3LYP/6-31G** (d,p) level of theory were calculated for three organic corrosion inhibitors [N-benzoyl-N-(p-aminophenyl) thiourea, N-benzoyl-N-(thiazole) thiourea and N-acetyl-N-(dibenzyl) thiourea. The calculated molecular descriptors such as the HOMO, LUMO, dipole moment, chemical potential (μ), chemical hardness (ղ), global nucleophilicity (ω) and average electronic charges on nitrogen atoms were explained in line with the experimental observed inhibitory efficiency for the compounds. The calculated results revealed that electron density on the rings (Qring (e)) and thiocarbonyl sulphur atom (S* in C=S) are strongly correlated to the observed %IE. Therefore, electronic interactions such as π-cationic and n-cationic interactions between the molecules and metal surface played prominent roles in adsorption process than electron donor-acceptor model as early reported by Uday et al., 2013 [19].

Simvastatin is a hypolipidemic drug used with exercise, diet and weight – loss to control elevated cholesterol or hypercholesterolemia. It is a member of the Statin class of pharmaceuticals. This paper delives voltammetric techniques is an electrochemical technique used in analytical applications and fundamental studies of electrode mechanism. This review summarizes some of the recent development and application of direct different electrodes in electrochemical for drug Simvastatin in their dosage forms and biological samples as reported in the period 1948 till 2017 years.