Corrosion Inhibition of Mild Steel in Acidic Solutions Using 1,2,4-Triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine

The inhibiting action, thermodynamics, and adsorptive properties of 1, 2, 4-triazolo[1, 5-a]pyrimidine (TP) have been investigated for the corrosion of mild steel in 0.5 M H₂SO₄ and 0.5 M H₃PO₄ solutions by means of potentiodynamic, electrochemical impedance spectroscopy techniques and quantum chemical calculations. Results obtained revealed that TP is more effective in 0.5 M H₃PO₄ than in 0.5 M H₂SO₄. Theoretical fitting of different adsorption isotherms such as Langmuir, Flory–Huggins, Temkin, and the kinetic-thermodynamic models were tested. The obtained experimental data fitted all the applied adsorption isotherms except Langmuir. The thermodynamic activation parameters were calculated. The potential of zero charge was also determined using AC measurements to clarify the nature of surface charge of the mild steel in both acidic solutions. Quantum chemical parameters were calculated and explained. The data explained that the inhibition of mild steel in both acidic solutions takes place through physicochemical adsorption mechanism.     

The role of chalcones: helichrysetin,xanthohumol, and flavokawin-C in promoting neurite outgrowth in PC12 Adh cells

Chalcones are a group of compounds widely distributed in plant kingdom. The aim of this study was to assess the neurite outgrowth stimulatory activity of selected chalcones, namely helichrysetin, xanthohumol and flavokawin-C. Using adherent rat pheochromocytoma (PC12 Adh) cells, the chalcones were subjected to neurite outgrowth assay and the extracellular nerve growth factor (NGF) levels were determined. Xanthohumol (10 μg/mL) displayed the highest (p < 0.05) percentage of neurite-bearing PC12 Adh cells and the highest (p < 0.05) NGF level in the culture medium of xanthohumol-treated cells. While, helichrysetin induced a moderately high numbers of neurite-bearing cells, flavokawin-C did not stimulate neurite outgrowth. This work supports the potential use of xanthohumol as a potential neuroactive compound to stimulate neurite outgrowth.     

Theoretical study of the low‐lying electronic states of the molecular ion KRb+

The potential energy curves of the molecular ion KRb⁺ have been investigated for the 60 lowest molecular states of symmetry ²Σ⁺, ²Π, ²Δ, and Ω = 1/2, 3/2, and 5/2. Using an ab initio method, the calculation has been done in a one active electron approach based on nonempirical pseudopotentials with core valence effects taken into account through parameterized l‐dependent polarization potentials. Using the canonicals functions approach a rovibrational study is done by calculating the eigenvalues E_v, the rotational constants B_v, the centrifugal distortion constants D_v (up to 135 vibrational levels), and the spectroscopic constants ω_e and B_e for the five electronic states (1)²Σ⁺, (3)²Σ⁺, (1)²Π, (1)Ω = 1/2, and (1)Ω = 3/2. No comparison of these values with other results is yet possible because they are given here for the first time. Extensive tables of energy values of E_v, B_v, and D_v are displayed at http://hplasim2.univ‐lyon1.fr/allouche . © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Al(H2PO4)3 as an efficient and reusable catalyst for the multi-component synthesis of highly functionalized piperidines and dihydro-2-oxypyrroles

Extremely facile and efficient procedures have been developed for the synthesis of highly functionalized piperidines and dihydro-2-oxypyrroles via one-pot multi-component reactions in the presence of Al(H₂PO₄)₃ as a heterogeneous and eco-friendly catalyst under mild conditions. The multi-component reaction of aromatic aldehydes, aromatic amines, and β-keto esters catalyzed by Al(H₂PO₄)₃ in EtOH at room temperature provides highly functionalized piperidines in good to excellent yields. The structure as well as the relative stereochemistry of these functionalized piperidines was confirmed by single X-ray crystallographic analysis. The same catalyst was found useful for the synthesis of polyfuntionalized dihydro-2-oxypyrroles using a four-component reaction of amines, dialkyl acetylenedicarboxylates and formaldehyde in MeOH at ambient temperature. It is found that the catalyst is recyclable and can be used up to five times without significant loss of its activity.     

ZnII and PbII coordination chemistry of 2,6-bis(1,2,3-triazol-4-yl)pyridine (clickate) and the metal ion-dependent emission of ‘clickate’–appended anthracene

The effect of metal coordination of 2-(1-(9-anthryl)methyl-1,2,3-triazol-4-yl)-6-(1-n-octyl-1,2,3-triazol-4-yl)pyridine (2) on the emission of the appended anthryl group was investigated in acetonitrile. The tridentate 2,6-bis(1,2,3-triazol-4-yl)pyridyl ligand included in 2 is referred herein as ‘clickate’. Titrating zinc(II) perchlorate or zinc(II) chloride into the solution of fluorescent ligand 2 results in quenching, which is attributed to the formation of a dark 1:1 Zn^II complex of 2. Frontier molecular orbital analysis and cyclic voltammetric data support the occurrence of photoinduced electron transfer from the excited state of the anthryl group to the Zn^II-bound clickate moiety, which relaxes the excited fluorophore non-radiatively, i.e. quenches fluorescence. Fluorescence quenching of clickate 2 upon forming the Pb^II complex was also observed. The Zn^II/Pb^II-coordination chemistry of clickate was characterised via X-ray crystallography, isothermal titration calorimetry, ¹H NMR spectroscopy and absorption spectroscopy using the symmetrically substituted clickate 2,6-bis(1-n-octyl-1,2,3-triazol-4 yl)pyridine (1).     

Lie‐group method for solving the problem of fission product behavior in nuclear fuel

Calculation of the gas atom concentration is an important feature of all physical models of fission gas release. We apply Lie‐group method for determining symmetry reductions to the diffusion equation describing the fission gas release from nuclear fuel. The resulting nonlinear ordinary differential equation is solved numerically using nonlinear finite difference method. Effects of the dimensionless group constant, the time, and the grain radius on the concentration diffusion function have been studied, and the results are plotted. It is found that the concentration of gas atoms increases as the dimensionless group constant, the power index, and the time increase, and it decreases with increase of the grain radius. Copyright © 2013 John Wiley & Sons, Ltd.     

SERS imaging of silver coated nanostructured Al and Al2O3 substrates. The effect of nanostructure

The last few years have witnessed rapid development of highly ordered and reproducible surface‐enhanced Raman scattering (SERS) nanostructured substrates for their potential medical and analytical application such as biosensing and bioimaging. In this work, 5‐nm silver films deposited on nanostructured Al and Al₂O₃ templates are investigated as substrates for SERS. The chosen templates show different honeycomb nanostructures with two sets of dimension, i.e. pore diameter of ca. 25 and 50 nm and interpore distance of ca. 56 and 100 nm. The SERS imaging results reveal that the signal of the probe molecule (4‐thiazolidinone‐2‐thione) is distributed inhomogeneously on the substrate surface, and this fact is correlated with the morphology of nanostructures determined by atomic force microscopy. The variation of SERS intensity among the substrates is strongly correlated with the shape and size of potential SERS‐active sites, e.g. nanocups and nanopores. The strongest SERS response is found for the Ag/Al₂O₃ template anodized in sulfuric acid, which represents the nanopore array with the smallest dimensions (e.g. pore diameter, interpore distance etc.). Furthermore, depending on size and nanostructure shape, changes in the adsorption mechanism of the probe molecule are observed. Copyright © 2014 John Wiley & Sons, Ltd.