Chemistry

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An [FeIII(biuret-amide)] complex has been immobilized onto mesoporous silica nanoparticles via Cu(I) catalyzed azide-alkyne click chemistry. This hybrid material functions as an efficient peroxidase mimic and was successfully used for the quantitative determination of hydrogen peroxide and glucose via a one-pot colorimetric assay. © 2012 Royal Society of Chemistry.

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(SoNS) School of Natural Sciences

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Chemical Communications

One pot glucose detection by [FeIII(biuret-amide)] immobilized on mesoporous silica nanoparticles: An efficient HRP mimic

A Matter of Density: Exploring the Electron Density Concept in the Chemical, Biological, and Materials Sciences

Introduction of Probability Concepts in Physics-The Path to Statistical Mechanics

Atoms in Molecules

Density Functional Approach to the Electronic Structure of Matter

Electron Density and Molecular Similarity

Time-resolved fluorescence Stokes shift and anisotropy measurements using a solvation probe in 0.78CH 3CONH 2 0.22{f LiBr (1-f) LiNO 3} melts reveal a strong decoupling of medium dynamics from viscosity. Interestingly, this decoupling has been found to occur at temperatures ∼50-100 K above the glass transition temperatures of the above melt at various anion concentrations (f LiBr). The decoupling is reflected via the following fractional viscosity dependence (η) of the measured average solvation and rotation times (τ s and τ r, respectively): τ x (ηT) p (x being solvation or rotation), with p covering the range, 0.20 p 0.70. Although this is very similar to what is known for deeply supercooled liquids, it is very surprising because of the temperature range at which the above decoupling occurs for these molten mixtures. The kinship to the supercooled liquids is further exhibited via p which is always larger for τ r than for τ s, indicating a sort of translation-rotation decoupling. Multiple probes have been used in steady state fluorescence measurements to explore the extent of static heterogeneity. Estimated experimental dynamic Stokes shift for coumarin 153 in these mixtures lies in the range, 1000 Δν tcm -1 1700, and is in semi-quantitative agreement with predictions from our semi-molecular theory. The participation of the fluctuating density modes at various length-scales to the observed solvation times has also been investigated. © 2012 American Institute of Physics.

Journal of Chemical Physics

Medium decoupling of dynamics at temperatures ∼100 K above glass-transition temperature: A case study with (acetamide + lithium bromidenitrate) melts

Steady state and time resolved fluorescence emission spectroscopy have been employed to investigate the effects of solvent confinement and electrolyte concentration on excited state intramolecular charge transfer (ICT) reaction in 4-(1-pyrrolidinyl) benzonitrile (P5C), 4-(1-piperidinyl) benzonitrile (P6C), and 4-(1-morpholenyl) benzonitrile (M6C) in AOT/n-heptane/acetonitrile and AOT/n-heptane/methanol reverse micelles. Dramatic confinement effects have been revealed via a huge reduction (factor ranging between 100 and 20) over bulk values of both equilibrium and reaction rate constants. A strong dependence on the size of the confinement (W s ) of these quantities has also been observed. W s dependent average static dielectric constant, viscosity and solvation time-scale have been determined. Estimated dielectric constants for confined methanol and acetonitrile show a decrease from the respective bulk values by a factor of 3-5 and viscosities increased by a factor of 2 at the highest W s considered. Addition of electrolyte at W s =5 for acetonitrile is found to produce a linear increase of confined solvent viscosity but leads to a non-monotonic electrolyte concentration dependence of average solvation time. Reaction rate constant is found to decrease linearly with electrolyte concentration for P5C and P6C but non-monotonically for M6C, the highest decrease for all the molecules being ∼ 20% over the value in the absence of added electrolyte in the solvent pool. The observed huge reduction in reaction rate constant is attributed to the effects of decreased solution polarity, enhanced viscosity and slowed-down solvent reorganization of the solvent under confinement in these non-aqueous reverse micelles. © 2011 Indian Academy of Sciences.

Journal of Chemical Sciences

Excited state intramolecular charge transfer reaction in non-aqueous reverse micelles: Effects of solvent confinement and electrolyte concentration#

Herein, we report a diversity-oriented-synthesis (DOS) approach for the synthesis of biologically relevant molecular scaffolds. Our methodology enables the facile synthesis of fused N-heterocycles, spirooxoindolones, tetrahydroquinolines, and fused N-heterocycles. The two-step sequence starts with a chiral-bicyclic-lactam-directed enolate-addition/substitution step. This step is followed by a ring-closure onto the built-in scaffold electrophile, thereby leading to stereoselective carbocycle- and spirocycle-formation. We used in silico tools to calibrate our compounds with respect to chemical diversity and selected drug-like properties. We evaluated the biological significance of our scaffolds by screening them in two cancer cell-lines. In summary, our DOS methodology affords new, diverse scaffolds, thereby resulting in compounds that may have significance in medicinal chemistry. Uno, DOS, tres: An enolate-mediated strategy was used to synthesize biologically relevant cyclic scaffolds. In silico analysis was used to evaluate the compounds in terms of, for example, polar surface area and chemical diversity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemistry - An Asian Journal

Reagent-based DOS: Developing a diastereoselective methodology to access spirocyclic- and fused heterocyclic ring systems

Recent advances in radical azidation using sulfonyl azides are presented. For instance, radical carboazidation using $\alpha$-iodoketones, desulfitative carboazidation and anti- Markovnikov hydroazidation of alkenes are described. These novel methods tolerate a large number of functional groups and allow the synthesis of organic azides that would be difficult to synthesize otherwise. The transformation of the azides using reductive processes as well as a Schmidt reaction under nonacidic conditions were used to synthesize alkaloids including indolizidine 167B, monomorine I, cylindricine C and lepadiformine C. {\textcopyright} 2012 IUPAC.

Pure and Applied Chemistry

Radical azidation reactions and their application in the synthesis of alkaloids

The peroxidase family of natural enzymes facilitate H2O 2 reduction by one electron transfer through aromatic substrates, if chromogenic, they can be used in the colorimetric detection of H 2O2 and subsequently glucose in tandem with glucose oxidase. Au nanoparticles encapsulated within porous silica exhibited peroxidase mimetic activity and kinetic parameter evaluation indicates an excellent affinity for H2O2. It is also shown to have a detection capability for glucose in very low concentrations and could be used for glucose detection in a one-pot assay. The material is synthesised by using cation-ended thiol-stabilised ultra small gold clusters as precursors. Removal of the thiols creates micropores within the silica, making this material unique in that the active centres are protected inside the silica, yet are accessible to reactant molecules. This characteristic makes the material ideal as a detection tool where attrition resistance will be advantageous. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012.