Department of Chemistry

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IIT Jodhpur

RSnCl3 (R = 2-phenylazophenyl) on reaction with Na2S·9H2O in a 1:1 mixture of acetone and methanol afforded a tetranuclear monoorganotin sulfide cage [(RSnIV)4(μ-S)6]· 2CHCl3·4H2O (R = 2-phenylazophenyl) (1). Complex 1 crystallizes in the monoclinic space group P2/n. The molecular structure of 1 contains five-coordinate tin centers in distorted trigonal bipyramidal geometry. Complex 1 is monoorganotin sulfide derivative having a tetranuclear double-decker cage-like structure. In 1, four tin centers are bridged by a μ2-S unit affording a ubiquitous Sn−S−Sn motif among monoorganotin sulfide compounds. In addition, each tin also has intramolecular coordination to a nitrogen atom of a 2-phenylazophenyl substituent (N → Sn). The DFT calculation suggests that the complex 1 involves mainly ligand based transitions. The complex 1 based device was studied for its electrical behavior and was found to show stable, reproducible memristive behavior with an on−off ratio of 103, which suggests that the complex 1 is a promising material for memory device applications. © 2019 American Chemical Society

World University root node

Department of Physics

ACS Applied Electronic Materials

Molecular Memory Switching Device Based on a Tetranuclear Organotin Sulfide Cage [(RSnIV)4(μ-S)6]·2CHCl3·4H2O (R = 2-(Phenylazo)phenyl): Synthesis, structure, DFT studies, and memristive behavior

An organophotoredox catalyzed efficient and robust approach for the synthesis of highly important 3-alkyl substituted chroman-4-one scaffold is developed using visible light induced radical cascade cyclization strategy. The reaction is initiated through the generation of alkyl radicals from N-(acyloxy)phthalimides under photoredox conditions, which subsequently undergo intermolecular cascade radical cyclization on 2-(allyloxy)arylaldehydes to afford chroman-4-one scaffolds. The presented strategy is attractive with regard to mild reaction conditions, operational simplicity, high functional group tolerance and broad substrate scope. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chemistry - An Asian Journal

Organophotoredox-Catalyzed Cascade Radical Annulation of 2-(Allyloxy)arylaldehydes with N-(acyloxy)phthalimides: Towards Alkylated Chroman-4-one Derivatives

A major unanswered question is how a TCR discriminates between foreign and self-peptides presented on the APC surface. Here, we used in situ fluorescence resonance energy transfer (FRET) to measure the distances of single TCR–pMHC bonds and the conformations of individual TCR–CD3ζ receptors at the membranes of live primary T cells. We found that a TCR discriminates between closely related peptides by forming single TCR–pMHC bonds with different conformations, and the most potent pMHC forms the shortest bond. The bond conformation is an intrinsic property that is independent of the binding affinity and kinetics, TCR microcluster formation, and CD4 binding. The bond conformation dictates the degree of CD3ζ dissociation from the inner leaflet of the plasma membrane via a positive calcium signaling feedback loop to precisely control the accessibility of CD3ζ ITAMs for phosphorylation. Our data revealed the mechanism by which a TCR deciphers the structural differences among peptides via the TCR–pMHC bond conformation. © 2019, CSI and USTC.

Fulltext

Cellular and Molecular Immunology

TCR–pMHC bond conformation controls TCR ligand discrimination

A Nonlinear Energy Sink (NES) having essential nonlinear stiffness, it is nonlinearly attached to a primary system. In contrast to Tuned Mass Damper, the NES could be capable over a wider frequency range and only require a small additional mass. NES have good potential for vibration mitigation and energy harvesting. One of the most common energy sources in an environment is ambient vibration. Some micro electro-mechanical system with magnetostrictive or piezoelectric materials is used to convert ambient vibration into electrical energy. That can be stored and used to power other devices such as wireless sensors, health monitoring sensors or replacing small batteries that have a finite lifespan or would require difficult and expensive maintenance. This study focuses on materials for energy harvesting with NES. Piezoelectric materials have a good capability to convert the mechanical vibration energy into electrical energy and vice versa; therefore, they are more suitable for energy harvesting with NES. A state of the art review of the piezoelectric material frequently used in NES coupled energy harvester with their relative merit is presented. (C) 2019 Elsevier Ltd. All rights reserved.

Department of Mechanical Engineering

MATERIALS TODAY-PROCEEDINGS

Materials for energy harvesting with a nonlinear energy sink: A literature review

γ-Ketohydroperoxide [3-(hydroperoxy)propanal] is an important reagent in synthetic chemistry and, in particular, oxidation reactions. It is considered to be a precursor for secondary organic aerosol formation in the troposphere. Due to enhanced reactivity and limitations associated with analytical techniques, theoretical methods have been employed to study the unimolecular reactivity of hydroperoxides. A number of automated reaction discovery techniques have been used to study the reactivity of γ-ketohydroperoxide, and a large number of reactions have been reported in such studies. In the present work, we have investigated the unimolecular reaction dynamics of this molecule using electronic structure theory calculations and direct chemical dynamics simulations to assess the relevance of different reaction pathways. Classical trajectories were launched from the reactant well with fixed amounts of total energies and integrated on-the-fly using density functional B3LYP/6-31+G∗ model chemistry. Three dissociation channels among the previously reported reactions were identified as important. Korcek decomposition, which was proposed earlier as a source of carbonyl compounds from thermal decomposition of γ-ketohydroperoxide, was not observed in the present high-temperature simulations. However, trajectories showed the formation of carbonyl compounds such as aldehydes via other pathways. Results are compared with previous studies, and detailed atomic-level reaction mechanisms are presented. © 2020 American Chemical Society.

Journal of Physical Chemistry A

Unimolecular Dissociation of γ-Ketohydroperoxide via Direct Chemical Dynamics Simulations

We report the effect of Co incorporation into a SiO2-Al2O3 supported catalytic system on the conversion, selectivity, and stability for the catalytic conversion of methyl oleate into diesel grade hydrocarbons with systematic changes in reaction parameters including temperature, time and hydrogen pressure. A series of cobalt loaded (4-12 wt\%) SiO2-Al2O3 catalysts were prepared by a simple wet impregnation method. The formation of a Co3O4 active catalyst phase and its homogenous dispersion on the SiO2-Al2O3 surface is revealed successively by XRD and TEM. The results showed that the formation of a Co3O4 phase over CoO/Co, the amount of Co loading, reaction time, temperature and H-2 pressure greatly determine the conversion and selectivity. Total ester conversions with more than 50\% selectivity towards n-heptadecane/n-octadecene were achieved at a temperature as low as 280 degrees C and 15 bar H-2 pressure within 10 h using a 6\% cobalt loaded catalyst. Significant hydrocracking was observed at higher metal loading under similar reaction conditions.

SUSTAINABLE ENERGY \& FUELS

Catalytic conversion of methyl oleate to hydrocarbons: impact of cobalt oxide species integration in SiO2-Al2O3

The catalytic deoxygenation of biomass to produce renewable carbon energy addresses major concerns of limited energy sources. In particular, the second-generation biodiesel by selective deoxygenation possesses a higher cetane number, lower cloud point, and higher oxidation stability compared to the fatty acid ester-based biodiesel, and therefore, can be fed directly to the current diesel engines. In present work, we address the significant concerns of cost-effectiveness, high hydrodeoxygenation (HDO) selectivity, modest hydrogen environments, and solvent-free condition using high surface area silica-alumina-supported cobalt oxide nanoparticles as a catalyst to produce fuel-grade hydrocarbons from fatty acid-based feeds that are palm oil and jatropha oil. The catalytic performance is tested for methyl stearate to achieve the best conversion efficiency with remarkable deoxygenation selectivity. The HDO selectivity was as high as 87\% at 250 degrees C and 30 bar H-2 pressure, whereas moderate HDO selectivity with relatively higher cracking was observed at 300 degrees C and 2 bar H-2 pressure. Remarkably, the HDO selectivity was comparable in the absence of solvent. The catalyst is recyclable with low metal leaching during the deoxygenation. The use of non-noble metal catalysts under solvent-free conditions offers facile production of fuel-grade hydrocarbons.

FUEL

Highly selective Co3O4/silica-alumina catalytic system for deoxygenation of triglyceride-based feedstock

Since the exposure of organophosphate pesticides are known to cause severe health consequences, it is important to understand the molecular interaction of these pesticides metabolites with vital biomolecules, especially with the proteins. Here, considering bovine serum albumin (BSA) as a model protein, we have examined its interaction with two selected organophosphate metabolites, 3,5,6-trichloro-2-pyridinol (TCPy) and paraoxon methyl (PM). TCPy and PM are resultant metabolites of two most widely used organophosphate pesticides chlorpyrifos and parathion respectively. 1H NMR line broadening, selective spin-lattice relaxation rate measurements, saturation transfer difference (STD) NMR of both TCPy and PM were carried out in the presence and absence of BSA. The obtained values of the affinity index (A), binding constants (Ka) and thermodynamic parameters indicated strong organophosphates-BSA interaction. Further, fluorescence quenching data on TCPy-BSA and PM-BSA interactions strongly supported the NMR results, besides providing the stoichiometry of these complexes. Molecular docking analysis unraveled viable, strong hydrogen bonds and electrostatic interactions in TCPy-BSA and PM-BSA complexes. This study also revealed substantial time-dependent changes in the 1H NMR intensity of PM in the presence of BSA, which suggests faster degradation of PM with increasing protein concentration during protein-metabolite interactions. The hydrolysis is attributed to the esterase-like action of BSA. The result provides key insights into the direct interaction of the organophosphate metabolites with a biologically important carrier protein, serum albumin. © 2019 Elsevier Inc.

Pesticide Biochemistry and Physiology

In vitro interaction of organophosphate metabolites with bovine serum albumin: A comparative 1H NMR, fluorescence and molecular docking analysis

Understanding the coupling of a hydration layer and a lipid membrane is crucial to gaining access to membrane dynamics and understanding its functionality towards various biological processes. To find out how significant the mutual influence of the hydration layer and bilayer dynamics is, a fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) lipid bilayer is simulated atomistically in the presence of the TIP4P/2005 water model at 308 K. Interface water (IW) molecules are classified based on their continuous physical proximity or ability to form hydrogen bonds with different moieties of lipid heads. A gradient in retardation of translational mean square displacements is found to operate coherently for both IW and lipid components across the bilayer normal. Deviations from Gaussianity in van Hove correlation functions increase for the lipids and decrease for the IW from the tails to the heads. The IW molecules exhibit Fickian but intermittent dynamics due to coupled vibrations in the local cage formed by the hydrogen bonds with the lipid heads followed by decoupled translational jumps. Importantly, the differences in regional dynamics of lipid heads are clearly reflected in the dynamics of spatially resolved IW molecules physically close to the lipid heads, but not to the dynamics of the hydrogen bonded IW molecules far from the lipid heads. These analyses imply that spatially resolved interface water dynamics can act as a sensitive reflector of regional membrane dynamics occurring at sub ps to hundreds of ps time-scales for several important biological functions at physiological temperature in the future. © the Owner Societies 2020.

Physical Chemistry Chemical Physics

Dynamic coupling of a hydration layer to a fluid phospholipid membrane: intermittency and multiple time-scale relaxations

The disposal of organic waste materials such as polymers is a serious problem to natural ecosystems as some of them can be non-biodegradable and potentially toxic. Thus, there is immense interest in developing processes that convert waste polystyrene into useable carbon. In this work, we developed a unique approach for obtaining graphitic carbon from waste polystyrene as a raw carbon source. The conversion process is catalyzed using the Ni-butanethiolate ink in ultralow quantities under an optimized temperature (800 °C) in the presence of 5% hydrogen in nitrogen. Interestingly, macroporous sugar cubes are used as a soft template to hold polystyrene and the catalyst together during decomposition, eliminating the need for a high-pressure source for retaining carbon for graphitization at high temperatures. An additional step of hydrogen annealing for pyrolyzed carbon nullifies the surface effects and improves the graphitization, reduces the point defects, and enhances the crystallinity of carbon and electrical conductivity specifically required for an electric double-layer capacitor (EDLC). The SPC8H-based graphitic carbon electrode exhibits perfect rectangular cyclic voltammetry characteristics with a symmetric triangular charge−discharge curve and a specific capacitance of ∼158 F/g at 1 A/g. The two-electrode EDLC device demonstrated excellent cyclic stability with a capacitance retention of ∼90% even after 10,000 cycles. This study reveals that the trashed polystyrene waste could be transformed into highly crystalline, graphitic carbon electrodes for energy storage devices. This indeed offers an alternative and sustainable approach with a low price to high-performance ratio that can probably manage the issue of white pollution at a commercial scale. © 2020 American Chemical Society