Fabrication of magnetically separable palladium–graphene nanocomposite with unique catalytic property of hydrogenation

One step solvothermal route has been developed to prepare a well dispersed magnetically separable palladium–graphene nanocomposite, which can act as a unique catalyst against hydrogenation due to the uniform decoration of palladium nanoparticles throughout the surface of the magnetite–graphene nanocomposite and hence can be reused for several times. In addition to catalytic activity, palladium nanoparticles also facilitate the formation and homogeneous distribution of magnetite (Fe₃O₄) nanoparticles onto the graphene surfaces or else an agglomerated product has been obtained after the solvothermal reduction of graphene oxide in presence of Fe³⁺ alone.     

Synthesis and reactivity of enediyne–nucleobase hybrids: effect of intramolecular π-stacking

Three distinct classes of nucleobase-containing enediynes 1–9 with varying nature of the linker have been synthesized to explore the effect of π-stacking interaction in accelerating the rate of Bergman cyclization (BC). Chemical reactivity study, both experimental and computations demonstrated the important role that aromatic π-stacking interactions between the appended nucleobases within an enediyne frame play in lowering the activation barrier of Bergman cyclization.     

Fluoride ion sensing by an anion-π interaction

We report the discovery of a supramolecular interaction (anion-π and charge/electron transfer, CT/ET) involving fluoride ion and π-electron deficient colorless naphthalene diimide (NDI) receptors. Strong electronic interactions between lone-pair electrons of F(-) ion and π*-orbitals of the NDI unit lead to an unprecedented F(-)→NDI ET event, which produces an orange colored NDI(?-) radical anion. Further reduction of NDI(?-) by another F(-) ion produces a pink colored NDI(2-) dianion, rendering NDI a colorimetric F(-) sensor. Preorganization of two NDI units in overlapping positions using folded linkers improves their selectivity and sensitivity for the F(-) ion significantly, allowing F(-) detection at nM concentration in 85:15 DMSO/H(2)O solutions.     

Contractive Annulation: A Strategy for the Synthesis of Small,Strained Cyclophanes and Its Application in the Synthesis of [2](6,1)Naphthaleno[1]paracyclophane

A new synthetic strategy (contractive annulation) for the synthesis of highly strained cyclophanes has been conceived and its viability has been demonstrated through a nine‐step synthesis of [2](6,1)naphthaleno[1]paracyclophane from [2.2]paracyclophane.     

Unusual fluorescence spectral response of 1-(4-N,N-dimethylaminophenylethynyl)pyrene towards the thermotropic phase change in lipid bilayer membranes

The applicability of 1-(4-N,N-dimethylaminophenylethynyl)pyrene (DMAPEPy), a pyrene derivative showing intramolecular charge transfer, as a prospective probe for lipid bilayer membranes has been evaluated. High sensitivity of DMAPEPy to solvent polarity and viscosity makes it to act both as a polarity-sensitive probe and as a fluorescence anisotropy probe. The molecule shows high partition efficiency towards bilayer membranes in both solid gel as well as in the liquid crystalline phases. The emission spectrum, quenching experiment and lifetime data suggest bimodal distribution of DMAPEPy in the bilayer. Using the solvent polarity scales the polarity parameters of the two locations in lipid bilayer have been estimated. In the bilayer environment it exhibits remarkable spectral changes with temperature. The thermotropic phase change of the bilayer is sensitively monitored by fluorescence intensity as well as fluorescence anisotropy parameters. DMAPEPy is also capable of sensing the changes induced by membrane modifiers like cholesterol.     

Amending the Anisotropy Barrier and Luminescence Behavior of Heterometallic Trinuclear Linear [MIILnIIIMII] (LnIII=Gd,Tb, Dy; MII=Mg/Zn) Complexes by Change from Divalent Paramagnetic to Diamagnetic Metal Ions

The sequential reaction of a multisite coordinating compartmental ligand [2‐(2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino)‐2‐methylpropane‐1,3‐diol] (LH₄) with appropriate lanthanide salts followed by the addition of [Mg(NO₃)₂] ? 6 H₂O or [Zn(NO₃)₂] ? 6 H₂O in a 4:1:2 stoichiometric ratio in the presence of triethylamine affords a series of isostructural heterometallic trinuclear complexes containing [Mg₂Ln]³⁺ (Ln=Dy, Gd, and Tb) and [Zn₂Ln]³⁺ (Ln=Dy, Gd, and Tb) cores. The formation of these complexes is demonstrated by X‐ray crystallography as well as ESI‐MS spectra. All complexes are isostructural possessing a linear trimetallic core with a central lanthanide ion. The comprehensive studies discussed involve the synthesis, structure, magnetism, and photophysical properties on this family of trinuclear [Mg₂Ln]³⁺ and [Zn₂Ln]³⁺ heterometallic complexes. [Mg₂Dy]³⁺ and [Zn₂Dy]³⁺ show slow relaxation of the magnetization below 12 K under zero applied direct current (dc) field, but without reaching a neat maximum, which is due to the overlapping with a faster quantum tunneling relaxation mediated through dipole–dipole and hyperfine interactions. Under a small applied dc field of 1000 Oe, the quantum tunneling is almost suppressed and temperature and frequency dependent peaks are observed, thus confirming the single‐molecule magnet behavior of complexes [Mg₂Dy]³⁺ and [Zn₂Dy]³⁺.     

Chalcogels: porous metal-chalcogenide networks from main-group metal ions. Effect of surface polarizability on selectivity in gas separation

We report the synthesis of metal-chalcogenide gels and aerogels from anionic chalcogenide clusters and linking metal ions. Metal ions such as Sb(3+) and Sn(2+), respectively chelated with tartrate and acetate ligands, react in solution with the chalcogenide clusters to form extended polymeric networks that exhibit gelation phenomena. Chalcogenide cluster anions with different charge densities, such as [Sn(2)S(6)](4-) and [SnS(4)](4-), were employed. In situ rheological measurements during gelation showed that a higher charge density on the chalcogenide cluster favors formation of a rigid gel network. Aerogels obtained from the gels after supercritical drying have BET surface areas from 114 to 368 m(2)/g. Electron microscopy images coupled with nitrogen adsorption measurements showed the pores are micro (below 2 nm), meso (2-50 nm), and macro (above 50 nm) regions. These chalcogels possess band gaps in the range of 1.00-2.00 eV and selectively adsorb polarizable gases. A 2-fold increase in selectivity toward CO(2)/C(2)H(6) over H(2) was observed for the Pt/Sb/Ge(4)Se(10)-containing aerogel compared to aerogel containing Pt(2)Ge(4)S(10). The experimental results suggest that high selectivity in gas adsorption is achievable with high-surface-area chalcogenide materials containing heavy polarizable elements.     

Hexanuclear Zn(II) and Mononuclear Cu(II) Complexes containing imino phenol ligands: Exploitation of their Catalytic and Biological Perspectives

A unique hexanuclear zinc(II) ( 1 ) and two mononuclear copper(II) ( 2 and 3 ) complexes anchored with imino phenol ligand HL ¹ and HL ² were synthesized with good yield and purity (where HL ¹  = 4‐tert‐butyl‐2,6‐bis((mesitylimino)methylphenol and HL ²   =  5‐tert‐butyl‐2‐hydroxy‐3‐((mesitylimino)methyl)benzaldehyde). These complexes were characterized by utilizing various spectroscopic protocols like NMR, FTIR, UV as well as ESI‐Mass spectrometry, elemental analysis and single crystal X‐ray diffraction studies. Their potential to bind calf thymus DNA (CT‐DNA) was tested utilizing different techniques such as UV–visible and fluorescence spectroscopy. The experiment implies that they interact with CT‐DNA via non‐intercalative mode with moderate capabilities (K_b ~ 10⁴ M^?1). On the other hand, these complexes have high capabilities to quench the fluorescence of bovine serum albumin (BSA) following the static pathway. In addition, they are active catalysts for the oxidation reaction of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to 3,5‐di‐tert‐butylquinone (3,5‐DTBQ) under aerobic condition. From the recorded EPR signals of all complexes, it has been concluded that the oxidation reaction proceeds via ligand oriented radical pathway instead of metal based redox participation. Kinetic studies using 1 – 3 indicate that it follows Michaelis–Menten type of equation with moderate to high turnover number (k_cat). Apart from these aspects, complexes 1 – 3 were screened for their cytotoxic behavior towards HeLa cells (human cervical carcinoma) and found quite active with comparable IC₅₀ values to cisplatin.     

Azadirachta indica leaves mediated green synthesized copper oxide nanoparticles induce apoptosis through activation of TNF-α and caspases signaling pathway against cancer cells

Green nanotechnology elucidates highly prioritized anticancer activity. We synthesized Copper oxide nanoparticles (CuONPs) using leaves of Azadirachta indica (A. indica) plants and studied the molecular mechanism of cancer cell apoptosis. After their synthesis, with the help of expository tools like Fourier transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM), Dynamic light scattering (DLS) and surface zeta potential we confirmed the successful synthesis of CuONPs. Here, crystalline structure of green synthesized CuONPs of 36?±?8?nm size and spherical shape was able to kill MCF-7 and Hela cells, estimated by MTT assay. Successful internalization of Cu⁺² ions inside the cell was estimated by the atomic absorption study. Cellular uptake of Cu⁺² ions inflicted significant Reactive Oxygen Species (ROS) generation inside the cancer cells, thereby leading to DNA fragmentation as observed by DAPI staining. In in vivo model, CuONPs reduced the breast tumor volume in Balb/C mice and increased the mean survival time through the alteration of pro-inflammatory cytokines level. In case of both in vivo and in vitro models, CuONPs altered the pro-inflammatory cytokine level and pro-apoptotic protein expressions. In future, green synthesized CuONPs might be beneficial for its application as an anticancer drug in in vivo (mice model) and in vitro, though further study is needed on its toxicity.