A General Catalyst Based on Cobalt Core–Shell Nanoparticles for the Hydrogenation of N-Heteroarenes Including Pyridines

Herein, we report the synthesis of specific silica-supported Co/Co₃O₄ core–shell based nanoparticles prepared by template synthesis of cobalt-pyromellitic acid on silica and subsequent pyrolysis. The optimal catalyst material allows for general and selective hydrogenation of pyridines, quinolines, and other heteroarenes including acridine, phenanthroline, naphthyridine, quinoxaline, imidazo[1,2-a]pyridine, and indole under comparably mild reaction conditions. In addition, recycling of these Co nanoparticles and their ability for dehydrogenation catalysis are showcased.     

Synthesis,characterization, molecular docking and biological activity of 5,6-bis-(4-fluoro-phenyl)-3,4,7,8-tetraaza-bicyclo[8.3.1]tetradeca-1(13),4,6,10(14),11-pentaene-2,9-dione and its transition metal complexes

Macrocyclic Schiff base ligand through the condensation of 1,3-dicarbonyl-phenyl-dihydrazide with 4,4′-difluorobenzil and its Co(II), Ni(II), Cu(II) and Zn(II) metal complexes have been synthesized. The ligand and metal complexes were characterized by analytical and physicochemical methods. An octahedral geometry arising from coordination of N2O2 donor atoms from the macrocyclic framework has been proposed for all metal complexes. Synthesized ligand and metal complexes were investigated for in vitro antibacterial and antioxidant activity. Complex [Ni(C₂₂H₁₄N₄F₂O₂)(OCOCH₃)₂] has shown remarkable antibacterial activity (Minimum inhibitory concentration 8–16?μg/ml) comparable to commercial antibiotic Ciprofloxacin. Anticancer activity of synthesized compounds against Squamous Cell Carcinoma (SCC4), head and neck cancer cell line has also been studied at different concentrations and at different time points. Complexes [Co(C₂₂H₁₄N₄F₂O₂)(NO₃)₂] and [Cu(C₂₂H₁₄N₄F₂O₂)(OCOCH₃)₂] have shown remarkable anticancer results (IC₅₀ 31.1 and 43.1?μM) against the tested cell line in concentration dependent manner. Molecular docking studies were carried out to find the binding mode of the synthesized macrocyclic Schiff base ligand to Epidermal Growth Factor Receptor (EGFR) Kinase (PDB ID: 1M17).     

Validated LC–MS/MS method for quantification of agomelatine in human plasma and its application in a pharmacokinetic study

An analytical method based on liquid–liquid extraction has been developed and validated for analysis of agomelatine in human plasma. Fluoxetine was used as an internal standard for agomelatine. A Betasil C18 (4.0 × 100 mm, 5 µm) column provided chromatographic separation of analytes followed by detection with mass spectrometry. The method involves simple isocratic chromatographic conditions and mass spectrometric detection in the positive ionization mode using an API‐4000 system. The proposed method has been validated with linear range of 0.050–8.000 ng/ml for agomelatine. The intra‐run and inter‐run precision values are within 12.12% and 9.01%, respectively, for agomelatine at the lower limit of quantification level. The overall recovery for agomelatine and fluoxetine was 67.10% and 72.96%, respectively. This validated method was used successfully for analysis of plasma samples from a pharmacokinetic study. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of surfactant and annealing temperature on optical properties of sol–gel derived nano-crystalline TiO2 thin films

Titanium dioxide thin films have been synthesized by sol–gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 °C. The influence of surfactant and annealing temperature on optical properties of TiO₂ thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO₂ films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO₂ films was estimated by Tauc's method at different annealing temperature.     

General and selective synthesis of primary amines using Ni-based homogeneous catalysts

The development of base metal catalysts for industrially relevant amination and hydrogenation reactions by applying abundant and atom economical reagents continues to be important for the cost-effective and sustainable synthesis of amines which represent highly essential chemicals. In particular, the synthesis of primary amines is of central importance because these compounds serve as key precursors and central intermediates to produce value-added fine and bulk chemicals as well as pharmaceuticals, agrochemicals and materials. Here we report a Ni-triphos complex as the first Ni-based homogeneous catalyst for both reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes to prepare all kinds of primary amines. Remarkably, this Ni-complex enabled the synthesis of functionalized and structurally diverse benzylic, heterocyclic and aliphatic linear and branched primary amines as well as aromatic primary amines starting from inexpensive and easily accessible carbonyl compounds (aldehydes and ketones) and nitroarenes using ammonia and molecular hydrogen. This Ni-catalyzed reductive amination methodology has been applied for the amination of more complex pharmaceuticals and steroid derivatives. Detailed DFT computations have been performed for the Ni-triphos based reductive amination reaction, and they revealed that the overall reaction has an inner-sphere mechanism with H₂ metathesis as the rate-determining step.

A Ni-triphos based homogeneous catalyst enabled the synthesis of all kinds of primary amines by reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes.     

A Hybrid Monte‐Carlo sampling smoother for four‐dimensional data assimilation

This paper constructs an ensemble‐based sampling smoother for four‐dimensional data assimilation using a Hybrid/Hamiltonian Monte‐Carlo approach. The smoother samples efficiently from the posterior probability density of the solution at the initial time. Unlike the well‐known ensemble Kalman smoother, which is optimal only in the linear Gaussian case, the proposed methodology naturally accommodates non‐Gaussian errors and nonlinear model dynamics and observation operators. Unlike the four‐dimensional variational method, which only finds a mode of the posterior distribution, the smoother provides an estimate of the posterior uncertainty. One can use the ensemble mean as the minimum variance estimate of the state or can use the ensemble in conjunction with the variational approach to estimate the background errors for subsequent assimilation windows. Numerical results demonstrate the advantages of the proposed method compared to the traditional variational and ensemble‐based smoothing methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and in vitro biology of Co(II), Ni(II), Cu(II) and Zinc(II) complexes of functionalized beta-diketone bearing energy buried potential antibacterial and antiviral O,O pharmacophore sites

The clinically active functionalized β-diketones 1-(2′,4′-dihydroxyphenyl)-3-(2″-substitutedphenyl)-propane-1,3-dione (L₁)–(L₂) have been synthesized from Baker–Venkataraman transformation of 2,4-diaroyloxyacetophenones. Their transition metal complexes (1)–(8) have been prepared and characterized by physical, spectral and analytical data. The functionalized beta-diketone potentially acts as bidentate ligand and co-ordinate with the transition metal atom through beta-diketo system. The complexes have general formula [ML₂] where M = Co(II), Ni(II), Cu(II), Zinc(II) and L = ligand. The 1-(2′,4′-dihydroxyphenyl)-3-(2″-substitutedphenyl)-propane-1,3-dione and their transition metal complexes have been screened for in vitro antibacterial, antifungal and antioxidant bioassay. The biological activity data show that the transition metal complexes are more potent antibacterial, antifungal and antioxidant agents than the parent functionalized beta-diketone against different bacterial and fungal species. This constitutes a new group of compounds that can be used as potential metal derived drugs. Ultimately, here we can prompt about the use of metals for the drugs. The metal complexes were also studied for their thermogravimetric analyses.     

Field emission studies of silver nanoparticles synthesized by electron cyclotron resonance plasma

Field emission has been studied for silver nanoparticles (25-200 nm), deposited within a cylindrical silver target in an electron cyclotron resonance (ECR) plasma. Particle size distribution was controlled by optimum biasing voltages between the chamber and the target. Presence of non-oxidized silver was confirmed from the X-Ray diffraction analysis; however, thin protective layer of oxide was identified from the selective area electron diffraction pattern obtained with transmission electron microscopy. The silver nanoparticles were seen to exhibit hilly pointed like structures when viewed under the atomic force microscopy (AFM). The emissive properties of these particles were investigated by field emission microscopy. It is found that this technique of deposition is ideal for formation of nanoparticles films on different substrate geometries with size controllability as well as its application to emission devices.     

Chiron approach to the synthesis of yashabushidiol B, (3S,5S)-1-(4′-hydroxyphenyl)-7-phenylheptane-3,5-diol, and its 4′-methoxy analogue

The total synthesis of yashabushidiol B 4, a linear diarylheptanoid containing a 1,3-diol system and its analogues 5 and 6 has been achieved by utilizing intermediate 7, which was derived from d-glucose. The Wittig reaction is the key step of our synthetic strategy.