Lewis acid-mediated Michaelis-Arbuzov reaction at room temperature: a facile preparation of arylmethyl/heteroarylmethyl phosphonates

A facile preparation of arylmethyl and heteroarylmethyl phosphonate esters was achieved involving a Lewis acid mediated Michaelis-Arbuzov reaction at room temperature. Interaction of arylmethyl halides/alcohols with triethyl phosphite in the presence of Lewis acid at room temperature afforded phosphonate esters in good yields.     

Design and divergent synthesis of aza nucleosides from a chiral imino sugar

Several novel nucleoside analogues as potential inhibitors of glycosidases and purine nucleoside phosphorylase (PNP) have been synthesized via selective coupling of an appropriate nucleobase at different positions of an orthogonally protected imino sugar as a common precursor. This synthetic strategy offers a straightforward protocol for the assembly of imino sugar containing nucleosides, establishing a new repertoire of molecules as potential therapeutics.     

Signatures of Ge2Sb2Te5 film at structural transitions

Ge₂Sb₂Te₅ (GST) films, one of the most suitable Chalcogenide alloys for Phase change Random Access Memory applications are studied for changes in sheet resistance, optical transmission, morphology and surface science by annealing at various transition temperatures. The crystallization leads to an increase of grain size and roughness in the films and the resistance changes to three orders of magnitude. Optical studies on GST films show distinct changes during phase transitions and the optical parameters are calculated. An increase of Tauc parameters B^1/2 indicates a reduction in disorder during phase transition. It is confirmed from XPS studies that Ge-Te, Sb-Te bonds are present in both amorphous and crystalline phases whereas Sb-Ge, Te-Te, Sb-Sb bonds are absent.     

Manipulation of magnetic nanostructures through low temperature metal–oxygen chemistry: Co/CoO exchange biased nanodonuts and Co nanotips

Dense nanodonut and nanotip type morphologies are shown to self-evolve in ultrathin cobalt films during growth under vacuum, depending on the level of oxygen incorporation and temperature. The nanodonut morphology forms at room temperature and the corresponding magnetic hysteresis shows exchange bias (～35 Oe shift along the field axis), which is attributed to the presence of CoO and its exchange coupling with cobalt. The morphology evolves into nanotip features with increase of growth temperature, with concurrent elimination of the oxide component and exchange bias.     

Emissive Iridium(III) Complexes with Phosphorous‐Containing Ancillary

Ir(III) metal complexes and related emitters bearing all kind of cyclometalated chromophoric chelates and non‐chromophoric ancillary are extensively studied during the past three decades. Many of them have been found to display bright room temperature phosphorescence from triplet excited states in both solution and solid states, offering a possible application in contemporary optoelectronic technologies, including organic light emitting diodes, electrochemiluminescence, biological imaging and chemical sensing. Among reported materials, there are Ir(III) complexes with at least one phosphorus (P)‐containing ligand and/or ancillary chelate, together with cyclometalates or equivalents that are in control of the actual emission energy. Particularly, possession of P‐based donor can lead to divergent structural and photophysical properties compared to the traditional designs. This review aims to provide a literature overview as well as the authors’ personal account to the development of relevant Ir(III) based phosphors bearing these P‐donors. To the readers’ convenience, the contents are subdivided into six sessions, according to whether or not they are charge natural, or with mono‐ or dianionic electronic character, and in accordance to their divergent bonding modes, i. e. monodentate, bidentate and tripodal coordination. In many cases, the P‐based ancillaries offer an easy accessible route to the formation of efficient sky‐blue and true‐blue emitters due to their π‐accepting property, together with enlarged emission energy gap and destabilized upper lying quenching state.     

Catalytic reduction of organic dyes at gold nanoparticles impregnated silica materials: influence of functional groups and surfactants

Gold nanoparticles (Au NPs) in three different silica based sol–gel matrixes with and without surfactants are prepared. They are characterized by UV–vis absorbance and transmission electron microscopic (TEM) studies. The size and shape of Au NPs varied with the organo-functional group present in the sol–gel matrix. In the presence of mercaptopropyl functionalized organo-silica, large sized (200–280 nm) spherical Au NPs are formed whereas in the presence of aminopropyl functionalized organo-silica small sized (5–15 nm) Au NPs are formed inside the tube like organo-silica. Further, it is found that Au NPs act as efficient catalyst for the reduction of organic dyes. The catalytic rate constant is evaluated from the decrease in absorbance of the dye molecules. Presence of cationic or anionic surfactants greatly influences the catalytic reaction. The other factors like hydrophobicity of the organic dyes, complex formation of the dyes with anionic surfactants, repulsion between dyes and cationic surfactant, adsorption of dyes on the Au NPs also play important role on the reaction rate.     

DISPERSION-CORRECTED DENSITY FUNCTIONAL THEORY STUDIES ON GLYCOLIC ACID-METAL COMPLEXES

Journal of Structural Chemistry - The structure and metal complexation studies using dispersion-corrected density functional theory methods are performed for four stable glycolic acid conformers...