Synthesis,structural, spectroscopic,and thermal studies of some transition-metal complexes of a ligand containing the amino mercapto triazole moiety

A new series of transition-metal complexes of Schiff base ligand containing the amino mercapto triazole moiety ( HL ) was prepared. The Schiff base and its metal complexes were elucidated by different spectroscopic techniques (infrared [IR], ¹H nuclear magnetic resonance, UV–Visible, mass, and electron spin resonance [ESR]), and magnetic moment and thermal studies. Quantum chemical calculations have been carried out to study the structure of the ligand and some of its complexes. The IR spectra showed that the ligand is chelated with the metal ion in a neutral, tridentate, and bidentate manner using NOS and NO donors in complexes 1 – 6 , 10–12 , and 7 and 8 , respectively, whereas it behaves in a monobasic tridentate fashion using NOS donor sites in copper(II) nitrate complex ( 9 ). The magnetic moment and electronic spectra data revealed octahedral and square pyramidal geometries for complexes 2 , 11 , 12 , and 5 – 8 and 10 , respectively. However, the other complexes were found to have tetrahedral ( 4 ), trigonal bipyramidal ( 1 and 3 ), and square planar ( 9 ) structures. Thermal studies revealed that the chelates with different crystallized solvents undergo different types of interactions and the decomposition pathway ended with the formation of metal oxygen (MO) and metal sulfur (MS) as final products. The ESR spectrum of copper(II) complex 10 is axial in nature with hyperfine splitting with ²B_1g as a ground state. By contrast, complexes 7 and 8 undergo distortion around the Cu(II) center, affording rhombic ESR spectra. The HL ligand and some of its complexes were screened against two bacterial species. Data showed that complex 12 demonstrated a better antibacterial activity than HL ligand and other chelates.     

Synthesis of nano-sized zeolite-Y functionalized with 5-amino-3-thiomethyl 1H-pyrazole-4-carbonitrile for effective Fe(III)-chelating strategy

Zeolite crystals having faujasite-type (FAU) topology in the nanometer range were first synthesized from amorphous rice husk ash at a low temperature of 363 K under autogenous pressure. Following this, surface functionalization of the produced zeolite with 5-amino-3-thiomethyl 1H-pyrazole-4-carbonitrile (pyrazole; Py) was carried out by two different methods, namely liquefied-period adsorption of Py (Py/Y_im) and a flexible ligand method (Py/Y_ss). The latter provides a larger amount of Py formed into as-made zeolite-Y. The sorption of Fe(III) onto Py/NaY afforded large meso–macroporosity introduced by the aggregation–assembly between Fe(III)Py complexes and NaY zeolite, which was typically evidenced for Fe(III)Py/Y_ss. The materials were characterized by XRD, FT-IR spectroscopy, thermal analysis (TGA) and porous structure by N₂ adsorption–desorption at 77 K. The XRD evaluation showed that the zeolite structure was managed right after adding Fe(III) to Py/Y, although a change in intensity of the zeolite reflections on complex formation was noticed. The FT-IR spectrum of Fe(III)Py/Y_ss exhibited two bands at 3594 and 3542 cm^?1 assigned to bridging hydroxyl groups associated with a Brönsted site, which did not exist in the spectra of Fe(III)Py/Y_im and Fe(III)-exchanged as-made NaY zeolite. This effect was ascribed to the induced greater electronegativity of the ligand towards Fe(III) species in dissociation of water molecules, producing acidic protons that are potential Brönsted acid sites. It was also evident that the Fe(III) adsorption capacity on Py/Y_ss is greater than on as-made NaY zeolite and Py/Y_im, owing most likely to the increasing concentration of the incorporating Py ligand which leads to an increase in the number of binding sites. The Fe(III) adsorption onto Py/Y_ss was well described by the pseudo-second-order kinetic model. Density functional theory (B3LYP/6-311G*) was performed to understanding the interaction mode of the ligand and complex with zeolite. The QSPR was calculated depending on the optimization geometries, frontier molecular orbitals, thermodynamic parameters, and global chemical reactivates, which were discussed for the studied compounds. The HOMOs, LUMOs and molecular electrostatic potentials were plotted to elucidate the interaction manner of the tested compounds with the zeolite. The nonlinear optical properties were elucidated via 1st and 2nd hyper-polarizabilities. The auto-degradation behavior was predicted for the complex, based on the ionization optional and bond dissociation enthalpy. The interactions between P_y and Fe(III)P_y with the zeolite surface have been described with molecular dynamics using a Monte Carlo simulation.     

Determination of lignans,phenolic acids and antioxidant capacity in transformed hairy root culture of Linum usitatissimum

Hairy root culture is a promising alternative method for the production of secondary metabolites. In this study, transformed root of Linum usitatissimum was established using Agrobacterium rhizogenes A4 strain from root cultures for lignans, phenolic acids and antioxidant capacity determination. Total lignin content (secoisolariciresinol diglucoside, secoisolariciresinol and matairesinol) was 55.5% higher in transformed root cultures than in the non-transformed root culture. Secoisolariciresinol was detected in higher concentration (2.107 μmol/g DM) in the transformed root culture than non-transformed culture (1.099 μmol/g DM). Secoisolariciresinol diglucoside and matairesinol were exclusively detected in the transformed root culture, but were not found in the non-transformed root culture. The overall production of phenolic acids in transformed roots was approximately 3.5 times higher than that of the corresponding non-transformed culture. Free radical scavenging DPPH˙ and ABTS˙⁺ assays showed 2.9-fold and 1.76-fold higher anti-oxidant activity in transformed root culture as compared to non-transformed.     

First raw transition metal complexes of salicylidene and 2-hydroxy-1-naphthylidene-N-cyanoacetohydrazone

Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of salicylidene-N-cyano-acetohydrazone H2L1 and 2-hydroxy-l-naphthylidene-N-cyanoacetohydrazone H2L2 have been prepared in ethanolic solution and characterized by analytical, spectral, magnetic susceptibility, molar conductivity and TGA measurements. The analytical data show that all the complexes derived from H2L1 and H2L2 are formed in molar ratios 1M:2L, except the complexes of Mn(II), Co(II) and Cu(II) acetates of H2L2 and the complexes of Mn(II), Co(II) and Ni(II) acetates and CuCl2 of H2L1 are formed in 1:1 molar ratios. The conductance data show that all metal complexes are non-electrolytes. Electronic absorption spectra and magnetic susceptibility measurements proved that the prepared complexes have octahedral configuration except [Co(HL2)OAc] which has tetrahedral structure. The ligand field parameters were calculated for the Co(II) and Ni(II) complexes and the data show that the covalent character of the metal ligand sigma-bond is low. The ESR parameters of the Cu(II) complexes at room temperature were calculated. Thermal TGA for some solid complexes are reported.     

First synthesis of selenadiazolo[3,4‐i] Benzazepine derivatives

5‐Methyl‐4‐nitro‐2,1,3‐benzoselenadiazole ( 1 ) was converted into (E)‐5‐(2‐dimethylamino)vinylbenzo‐[c](1,2,5)selenadiazole‐4‐amine ( 4 ) by initial treatment with dimethylformamide dimethyl acetal (DMFDMA) ( 2 ) followed by selective reduction using ammonium bromide in methanol. Compound 4 afforded the selenadiazolo[3,4‐i][1]benzazepine derivatives ( 7, 10, 13, 15 ) upon treatment with malononitrile ( 5 ), ethyl cyanoacetate ( 8 ) and cyanoacetamide ( 11 ) respectively.     

Temperature scanning ultrasonic velocity study of complex thermal transformations in solid lipid nanoparticles

The purpose of this study was to determine whether temperature scanning ultrasonic velocity measurements could be used to monitor the complex thermal transitions that occur during the crystallization and melting of triglyceride solid lipid nanoparticles (SLNs). Ultrasonic velocity ( u) measurements were compared with differential scanning calorimetry (DSC) measurements on tripalmitin emulsions that were cooled (from 75 to 5 degrees C) and then heated (from 5 to 75 degrees C) at 0.3 degrees C min (-1). There was an excellent correspondence between the thermal transitions observed in deltaDelta u/delta T versus temperature curves determined by ultrasound and heat flow versus temperature curves determined by DSC. In particular, both techniques were sensitive to the complex melting behavior of the solidified tripalmitin, which was attributed to the dependence of the melting point of the SLNs on particle size. These studies suggest that temperature scanning ultrasonic velocity measurements may prove to be a useful alternative to conventional DSC techniques for monitoring phase transitions in colloidal systems.     

Synthesis and photophysical properties of poly-(phenylenevinylene) dendrimers with a ruthenium tris-bipyridine core

The photophysical processes have been investigated in first, second and third generation dendrimers with poly-(phenylenevinylene) branches and a ruthenium tris-bipyridine core, RuDn (n = 1–3). These dendrimers show very efficient forward singlet–singlet energy transfer from the branches to the ruthenium core upon UV irradiation, with efficiencies of 0.99 for RuD1 and 0.88 for RuD2 and RuD3 in CH₂Cl₂. The RuDn dendrimers show a bi-exponential emission decay in CH₂Cl₂, when excited with a 460 nm light with short lifetimes, however, the emission decay lifetimes become mono-exponential in 10% Triton X-100 aqueous solution (τ = 840 ns for RuD1, 890 ns for RuD2 and 1120 ns for RuD3).     

An eco-friendly multi-analyte high-performance thin layer chromatographic densitometric determination of amoxicillin,metronidazole, and famotidine in their ternary mixtures and simulated gastric juice: A promising protocol for eradicating Helicobacter pylori

Gastrointestinal tract disorders constitute a heavy burden to healthcare providers. To eradicate Helicobacter pylori infection, different triple therapy protocols have been proposed. Among which are combinations of proton pump inhibitors (e.g., omeprazole), histamine-2 receptor antagonists (e.g., famotidine), along with antibiotics (e.g., amoxicillin). In this work, a sensitive and accurate high-performance thin-layer chromatographic method was developed for the simultaneous determination of amoxicillin, metronidazole, and famotidine in bulk powder and laboratory-prepared combined-tablet mixtures. Complete separation of the cited compounds was achieved using pre-coated silica gel plates with a mixture of methanol:chloroform:toluene:water:glacial acetic acid (5:2:1.5:0.5:0.1 v/v/v/v/v) as the mobile phase. The method was fully validated as per the international conference of harmonization guidelines. Good linearity, a correlation coefficient of 0.9991, was obtained in the concentration ranges 0.1–1.6 μg/band (amoxicillin), 0.1–0.9 μg/band (metronidazole), and 0.1–0.9 μg/band (famotidine). Since the method allowed the determination of the three compounds in combined tablets with a high degree of selectivity, accuracy, precision, with cost-effectiveness, it could be used for regular quality control. Moreover, the applicability of the proposed method was extended to the determination of the ternary mixture in simulated gastric juice. Method greenness was assessed using different green metrics.     

Determination of Esomeprazole on an Electropolymerized L‐arginine and β‐cyclodextrin Modified Screen Printed Carbon Electrode

The formation of an inclusion complex of the proton‐pump inhibitor (PPI) drug esomeprazole (ESO) with ß‐cyclodextrin (ß‐CD) has been investigated and proven by cyclic voltammetry (CV). The formation constant of the complex was determined. Thereafter, an electropolymerized β‐CD and L‐arginine (L‐arg) modified screen printed carbon electrode (P‐β‐CD‐L‐arg/SPCE) was developed for the determination of ESO using differential pulse adsorptive stripping voltammetry (DPAdSV). A significant enhancement of the peak current was observed when applying an accumulation step due to the effect of adsorption. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) further indicated that the polymer of β‐CD and L‐arg efficiently improved the electron transfer kinetic between analyte and electrode surface. Under the optimized conditions, the oxidation peak current was linearly proportional to the concentration of the drug in the range of 1.0×10^?8 to 1.0×10^?5 M. The DPAdSV method was successfully used to determine the concentrations of the drug in spiked human serum samples.