Synthesis and characterization of silica-gold core-shell (SiO<Subscript>2</Subscript>@Au) nanoparticles

This paper reports a systematic investigation of the growth and attachment of small gold nanoparticles to the functionalized surface of larger silica nanoparticles by three different methods. Nearly monodispersed silica particles and gold nanoparticles were prepared by sol-gel method. The size of the particle could be altered by changing the concentration of reactants, temperature and the time for which they react. The nanocoreshell particles prepared by three different methods were studied using scanning electron microscopy (SEM), UV-vis spectroscopy and Fourier transform infrared spectroscopy. We have found that the third method (c), a combination of the first two methods (a) and (b), has given better results.      

Analysis of thermal expansivity of iron (Fe) metal at ultra high temperature and pressure

In the present investigation we have explained the thermal and compression properties of HCP iron (Fe) at high pressure with variable temperature (isobars) and at high temperature with variable pressure (isotherm). The usual Tait equation of state is modified by incorporating the effect of thermal pressure. The calculated values of pressure for different isotherms and isochors and thermal expansivity (α) as a function of both temperature and pressure have been compared with those values obtained by Isaak et al and Wasserman et al.      

Kinetics and mechanism of ruthenium(III) catalysis in the oxidation of erythritol and dulcitol byN-bromoacetamide

Summary The kinetics of Ru^III catalysed oxidation of erythritol (1,2,3,4-tetrahydroxybutane) and dulcitol (1,2,3,4,5,6-hexahydroxyhexane) byN-bromoacetamide (NBA) in HClO₄ in the presence of Hg(OAc)₂ as a scavenger for Br^– have been investigated. The reactions are zeroth order with respect to both alcohols, and first order at low concentration of NBA tending to zero order at high NBA concentrations. The oxidation rate is directly proportional to [Ru^III] and a positive effect on the rate is observed for [H⁺] and [Cl^–] whereas a negative effect is observed for acetamide and ionic strength. D₂O and Hg(OAc)₂ do not influence the oxidation rate; (H₂OBr)⁺ is postulated as the oxidising species. A suitable mechanism consistent with the observed kinetic data is proposed.     

Synthesis,Molecular Docking and Potential Antioxidant Activity of Di/Trisubstituted Pyridazinone Derivatives

A number of pyridazinone derivatives bearing substituted benzylidene and heterocyclic/aromatic rings at 4^th and 6^th positions, respectively were synthesized in good to moderate yields and screened for antioxidant activity. Antioxidant activity of pyridazinone derivatives was evaluated by using several in vitro radical scavenging methods such as 1,1‐diphenylpicrylhydrazyl (DPPH), hydrogen peroxide (H₂O₂), nitric oxide (NO), reducing power, and metal chelating assay etc. Molegro virtual docker software was used to study the binding affinity of the title compounds with the xanthine oxidoreductase enzyme. Amongst the tested compounds, 5a, 5d, 5g & 5j were found to exhibit excellent antioxidant activity at par with the positive control, ascorbic acid. The molecular docking studies of these compounds demonstrated a good selectivity profile with xanthine oxidoreductase receptors. A preliminary study of the structural‐activity relationship showed that the presence of electron withdrawing group and heterocyclic ring on pyridazinone nucleus are associated with the best potency and selectivity profile. It could be proposed that xanthine oxidoreductase receptor may be involved in observed antioxidant activity of pyridazinone derivatives bearing aromatic ring and benzylidene substituents and thus the synthesized compounds are worthy of further exploration.     

C−H Bond Activation/Arylation Catalyzed by Arene–Ruthenium–Aniline Complexes in Water

Water‐soluble arene–ruthenium complexes coordinated with readily available aniline‐based ligands were successfully employed as highly active catalysts in the C?H bond activation and arylation of 2‐phenylpyridine with aryl halides in water. A variety of (hetero)aryl halides were also used for the ortho‐C?H bond arylation of 2‐phenylpyridine to afford the corresponding ortho‐ monoarylated products as major products in moderate to good yields. Our investigations, including time‐scaled NMR spectroscopy and mass spectrometry studies, evidenced that the coordinating aniline‐based ligands, having varying electronic and steric properties, had a significant influence on the catalytic activity of the resulting arene–ruthenium–aniline‐based complexes. Moreover, mass spectrometry identification of the cycloruthenated species, {(η⁶‐arene)Ru(κ²‐C,N‐phenylpyridine)}⁺, and several ligand‐coordinated cycloruthenated species, such as [(η⁶‐arene)Ru(4‐methylaniline)(κ²‐C,N‐phenylpyridine)]⁺, found during the reaction of 2‐phenylpyridine with the arene–ruthenium–aniline complexes further authenticated the crucial roles of these species in the observed highly active and tuned catalyst. At last, the structures of a few of the active catalysts were also confirmed by single‐crystal X‐ray diffraction studies.     

X-ray structure and temperature dependent luminescent properties of two bimetallic europium complexes

The structural, luminescent and temperature dependent luminescent properties of two homodinuclear europium complexes bridged by 2,2′-bipyrimidine (bpm) are reported. β-Diketonate ligands 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione (tfa) and 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (tta) are used as capping ligands resulting in complexes of the form [Eu(tfa)₃]₂bpm (1) and [Eu(tta)₃]₂bpm (2). All Eu^III ions are eight coordinate with six O atoms from the β-diketones and two N atoms from the polyazine bridging ligand. Excitation of the β-diketonate ligands tfa or tta at ca. 340 nm in toluene solutions results in the characteristic Eu^III emission in the visible region of the spectrum. The emission intensity and lifetime associated with the Eu^III centers decrease as the temperature of the solution is increased. Lifetime measurements are fit to a monoexponential while the temperature dependent lifetime data is fit to an Arrhenius-type equation. Evaluation of the data in comparison to data obtained from the monometallic Eu^III analogs reveal very similar photoluminescent properties. This suggests little electronic communication between Eu^III ions via the polyazine bpm bridging ligand.     

Novel Electrochemical Synthesis and Characterization of Zn(II) Metal Organic Framework for Photo-catalytic and Sensing Applications

Multidentate 1,3,5-benzenetricarboxylic acid (organic linker), Zn (II) based Zn-BTC has been synthesized via electrochemical method. Quantitative and Qualitative analyses of synthesized metal–organic framework (MOF) have been done using Fourier Transform Infrared (FTIR) Spectroscopy, Energy Dispersive X- Ray Spectroscopy (EDS), and Photoluminescence (PL). Powder X-Ray Diffraction (PXRD) and Scanning Electron Microscopy (SEM) have been used for crystallographic and morphological & topographical analyses, respectively. Crystallographic studies confirm the formation of face-centered cubic (fcc) crystal structure with good crystallinity. Photo-catalytic activity of synthesized MOF has been tested using Methylene Blue (MB) dye as a test contaminant in aqueous media under sunlight irradiation. Recorded results reveal that the synthesized MOF efficiently degrade MB dye upto 96% under sunlight exposure after 270 min. Photoluminescence studies indicate that Zn-BTC could be used as an efficient material for sensing of nitroaromatic compounds (NACs): 4-Nitroaniline (4-NA), 2-Nitroaniline (2-NA), 3- Nitroaniline (3-NA), 2,4-Dinitrotoulene (2,4-DNT), 4-Nitrotoulene (4-NT) in N,N’-Dimethylformamide (DMF) by fluorescence quenching and shows maximum quenching efficiency towards 3-NA (72.80%). Notably, the variation in luminescence intensity of 3-NA@Zn-BTC shows a linear relationship over its different concentrations from 0–1000 ppb range with K_SV?=?2.7?×?10⁴ M^?1 and R²?=?0.9924 with limit of detection 0.889 ppb (6.43 µM) (LOD). The possible ways of luminescence quenching are successfully explained by the combination of Photoinduced Electron Transfer (PET) and Resonance Energy Transfer (RET) mechanisms. Additionally, the Density Functional Theory (DFT) calculations have been employed to support the experimental results. Zn-BTC fully demonstrates the power of a multi component MOF, which provides a feasible pathway for the design of novel material towards fast responding luminescence sensing and photocatalytic degradation of pollutants.

Graphical Abstract

     

Study of Anti-Apoptotic mechanism of Ruthenium (II)Polypyridyl Complexes via RT-PCR and DNA binding

A set of novel mononuclear polypyridyl complexes of Ru (II) with N – N donar ligands 1, 10 phenanthroline (phen), 2, 2′ bipyridine (bpy), 4, 4′-dimethyl 2, 2′ bipyridine (dmb) and an intercalating ligand (bnpip = 2-(4-butoxy-3-nitrophenyl)-1H-imidazo [4,5-f] [1,10] phenanthroline) have been synthesized and characterized by various spectral methods. The RT - PCR assays suggest that ruthenium (II) complexes inhibit MCF-7, breast cancer cell line by inducing apoptosis via inhibition of cell cycle check points cyclin D, cyclin E and also upregulation of caspase 8 (protein involved in late Apoptosis). Further the binding potency of Ru (II) complexes were investigated using various spectroscopic techniques like UV–visible, fluorescence and viscosity studies. The complex binds to DNA in an intercalative mode as confirmed by viscosity data with differential binding strength. All complexes show cleavage of the pBR322 DNA through a singlet oxygen production. Theoretical evidence via docking of the complex with DNA reveals the significant residues of binding as guanine.     

Double Schiff bases derivatives of chitosan by selective C-6 and C-2 oxidation mediated by 5-fluorosalicylaldehyde aniline by TG-GC-MS and TG-FTIR analysis

Abstract

This enhancement in the activity may be efficient on the basis that ligands mainly possess CH=N bond. The use of a structure-based drug design approach (SBDD) provides a way for investigation as well as to understand the molecular basis of the target protein and ligand molecule interactions at the atomic level. Structure-based drug design is the design and optimization of a chemical structure to identify a compound suitable for clinical testing the drug candidates. Chitosan is a polysaccharide with recognized biological activities for improving the functionality of polysaccharide 5-Fluorosalicylaldehyde aniline system. The used for selectively oxidized chitosan to produce tailored derivatives. C-2-5-Fluorosalicylaldehyde-C-6 aniline double Schiff base derivatives of chitosan were synthesized. The structure and properties of the newly synthesized product were characterized by FT-IR, ¹H-NMR, ¹³C-NMR, GC-Mass spectroscopy, and thermal analysis (DSC/TGA). An exothermic process discusses a DSC and TGA analysis of thermal behavior of this polymer was shown to be a possible thermal polymerization of the double bonds in the polymer chains and thermo-oxidation of the polymer.