Department of Chemistry

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IIT Jodhpur

Synthesis of pyrazolo[1,5-c]quinazolines from four easily available precursors is presented through a one-pot tricyclic Pd(ii)/Ag(i) relay catalysis. The bimetallic relay cascade forges five new chemical bonds by concatenating six discrete chemical steps. The relay catalysis enables four-component assembly of pyrazolo[1,5-c]quinazolines that selectively inhibit EGFR, exhibit apoptosis through the ROS-induced mitochondrial-mediated pathway, and arrest the cell cycle at the G1 phase. © 2018 The Royal Society of Chemistry.

World University root node

Chemical Communications

Relay tricyclic Pd(ii)/Ag(i) catalysis: Design of a four-component reaction driven by nitrene-transfer on isocyanide yields inhibitors of EGFR

This brief proposes an event-triggered composite control of a two time scale system. A periodic sampling requirement is relaxed and both slow and fast states of the system decide independently when transmitting their current measurements based on a time-dependent triggering rule. The distinct feature of this scheme is that it does not require synchronized measurement updates of its slow and fast dynamics. Further, the theory of singular perturbation is used to decouple the system into slow and fast subsystems, and stability of the system is established. The proposed control strategy guarantees convergence of system states to an adjustable region around origin excluding the Zeno behavior. Simulation results manifest the effectiveness of the proposed approach. © 2004-2012 IEEE.

Department of Electrical Engineering

IEEE Transactions on Circuits and Systems II: Express Briefs

Event-Triggered Composite Control of a Two Time Scale System

In this study, a series of mineral and organic acids are introduced to natural clay modification. Several analytical techniques are employed to identify the physical and chemical changes in clay. The effect of surfactants on these properties is also investigated. The samples are prepared using simple acid treatment without filtration. The alteration in surface morphology is proportional to the acid strength as evident from SEM and XRD analyses. Therefore, the treatment with mineral acid and organic acid/HNO3 results in the formation of new layers by surface modification as depicted in SEM images, and a higher degree of suppression in characteristic XRD reflections of clay is noticed. However, the treatment with organic acids modifies the existing interlayer spacing of clay, and therefore, the XRD characteristic reflections of clay are less affected. These observations are also supported by FT-IR analysis. The surface area of modified clay is dependent on the acid strength, composition and size of counter-anion of acid. An increase in surface area and porosity is noticed after surfactant modification of HNO3-treated clay, where the change is more prominent at the concentration higher than their respective critical micelle concentration. Thermal stability is dependent on the chemical composition and surface area of clay materials. A relatively higher absorbance is observed for modified clay materials compared with untreated clay during DRS analysis. The catalytic efficiency of modified clay materials in Eriochrome Black T degradation has been demonstrated. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

Journal of Materials Science

On the investigation of acid and surfactant modification of natural clay for photocatalytic water remediation

Fluorinated α-Fe2O3 nanostructures are synthesized via a facile hydrothermal route using Selectfluor™ (F-TEDA) as a fluorinating as well as growth directing agent. The addition of incrementally increasing amount of F-TEDA to Fe precursor under hydrothermal conditions resulted in preferential growth of α-Fe2O3 along (110) orientation with respect to (104) direction by ~ 35%, the former being important for enhanced charge transport. On increasing fluorination, the heirarchical dendritic-type α-Fe2O3 changes to a snow-flake type structure (F-TEDA-20%) anisotropically growing along the six directions however, at higher F-TEDA concentrations (≥ 30%), loosely held particulate aggregates are seen to be formed. The X-Ray Photoelectron Spectroscopy (XPS) suggest the maximum fluorinarion of α-Fe2O3 at 1.21 at% in 30% F-TEDA. Further, optical absorption studies reveal reduction in optical band gap from 2.10 eV in case of pristine to 1.95 eV for fluorinated α-Fe2O3. A photoanode made by taking 20% fluorinated α-Fe2O3 in a ratio of 10:90 with respect to TiO2 (P-25) showed improved performance in dye sensitized solar cells with an increase in efficiency by ~16% in comparision to that of pristine Fe2O3 and TiO2. Furthermore, anode consisting of thin films of fluorinated α-Fe2O3 on FTO also exhibit enhanced current density on illumination of ~100 W/m2. The increase in photoelectrochemical activity seems to be due to the combination of two factors namely preferential growth of α-Fe2O3 along (110) direction resulting in an improved charge transfer efficiency and reduced recombination losses due to the presence of fluorine. © 2017 Elsevier B.V.

Solar Energy Materials and Solar Cells

Surface fluorination of α-Fe2O3 using selectfluor for enhancement in photoelectrochemical properties

Photocatalytic activity of low band gap hydrogenated HfO2 doped TiO2 (H-HfO2/TiO2), HfO2 doped TiO2 (HfO2/TiO2) and TiO2 (pristine) were investigated by photocatalytic degradation of five different industrial dyes. The current study envisages the effect of doping hydrogen and HfO2 up on TiO2 for photocatalytic degradation of different chemically structured dyes. Methylene Blue attains fast degradation efficiency of 90%, within 10 min of the reaction due to high photocatalytic adsorption and degradation over the rough TiO2 surface. Effect of pH on dye degradation is observed, leading to disintegration and mineralization. © 2018

Materials Letters

Heterostructured HfO2/TiO2 spherical nanoparticles for visible photocatalytic water remediation

In the present study, we attempt to characterize fluorinated ligand-serum albumin interaction in solution by a set of one-dimensional 19F ligand-based experiments. In this regard, a model system diflunisal (DFL)-human serum albumin (HSA) has been chosen to benchmark the utility of 19F relaxation and diffusion-based experiments in deciphering ligand-protein interactions. Further, we extend the application of a similar set of 19F experiments to unravel the molecular interaction in an unexplored system of 2,6-difluorobenzoic acid (DFBA)-bovine serum albumin (BSA). Interaction analysis of DFBA-SA is of particular interest because DFBA is not only a stable metabolite of a number of pesticides but also used as the starting reagent of many fluorinated drugs. Observation of 19F-1H &amp; 1H-1H saturation transfer difference effects confirmed binding of the ligands to SA. Further, these ligand-protein complexes were probed in terms of the dissociation constant (KD), number of binding sites (n), bound fraction of the ligand (Pb), the complex lifetime (Δres), and exchange rate (Kex). Although Carr-Purcell-Meiboom-Gill (CPMG)-based transverse relaxation and diffusion analysis quantified the former three quantities, the latter two were determined by the constant time fast pulsing CPMG method. Additionally, 19F competition binding experiments performed with well-characterized BSA site markers and DFBA indicated nonspecific binding of DFBA to BSA, whereas similar measurements in the case of HSA with DFL and DFBA revealed superior binding interaction of DFL with SA. © 2018 American Chemical Society.

Journal of Physical Chemistry B

Binding Interaction of Organofluorine-Serum Albumin: A Comparative Ligand-Detected 19F NMR Analysis

Perbenzoic acid (a weak organic acid) and its conjugate base (perbenzoate anion, C6H5C(O)O2−) are important organic reagents used extensively in synthetic chemistry. A few studies are available in the literature on the structure and reactivity of the perbenzoate anion. Gas phase dissociation of the perbenzoate anion and its substituted analogues by collision induced dissociation mass spectrometry experiments revealed carbon dioxide (CO2) loss as the major dissociation pathway. CO2 loss was proposed to occur via intramolecular nucleophilic attack by the negatively charged oxygen atom at the ipso or ortho position of the benzene ring. In the present work, we investigated decomposition pathways of perbenzoate anion in the gas phase via classical direct chemical dynamics simulations to establish the atomic level reaction mechanisms. Classical trajectories were integrated on-the-fly using the density functional B3LYP/6-31+G* level of electronic structure theory. Removal of CO3, CO2 from the perbenzoate anion and isomerization to an oxydioxirane intermediate were the primary reaction pathways observed in the simulations. In a major fraction of the trajectories, elimination of CO2 happened via initial CO3 loss from the perbenzoate anion followed by removal of O atom from the unstable neutral CO3 molecule. © 2018 Elsevier B.V.

International Journal of Mass Spectrometry

Theoretical study of perbenzoate anion decomposition pathways in the gas phase

Recent years have witnessed a resurgence of novel, efficient and practical protocols for radical-mediated cross-coupling reactions involving N-(acyloxy)phthalimides (NHPI esters) as redox-active esters. After the initial discovery of the redox-active properties of NHPI esters, exciting examples of SET-based cross-coupling reactions under thermal or photolytic conditions leading to diverse C–X (X=C, B, Si, Se, S) bonds have been published. The operational simplicity and broad applicability exhibited in redox-active NHPI ester-based cross-couplings bode well for their widespread adoption. The review presented herein covers all the recent developments in the field of redox-active ester (RAE)-based cross-couplings since the initial discovery. Depending on the conditions employed the reactions have been categorized into photoinduced and non-photoinduced cross-couplings with representative examples and insightful mechanistic discussions. (Figure presented.). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Advanced Synthesis and Catalysis

N-(Acyloxy)phthalimides as Redox-Active Esters in Cross-Coupling Reactions

Fluorescence in situ hybridization (FISH) is the primary technology used to image and count mRNA in single cells, but applications of the technique are limited by photophysical shortcomings of organic dyes. Inorganic quantum dots (QDs) can overcome these problems but years of development have not yielded viable QD-FISH probes. Here we report that macromolecular size thresholds limit mRNA labeling in cells, and that a new generation of compact QDs produces accurate mRNA counts. Compared with dyes, compact QD probes provide exceptional photostability and more robust transcript quantification due to enhanced brightness. New spectrally engineered QDs also allow quantification of multiple distinct mRNA transcripts at the single-molecule level in individual cells. We expect that QD-FISH will particularly benefit high-resolution gene expression studies in three dimensional biological specimens for which quantification and multiplexing are major challenges. © 2018, The Author(s).

Fulltext

Nature Communications

Enhanced mRNA FISH with compact quantum dots

Formamide (NH2CHO), being the simplest organic molecule containing an amide functional group, serves as a prototype to study protein and peptide chemistry. Formamide has been found in Comets and interstellar media and its decomposition results in smaller molecules such as NH3, CO, HCN, HNCO, etc. These smaller molecules are considered to have been potential precursors for the formation of complex biological molecules, such as nucleic acids and nucleobases, in the early Earth. Several experimental and theoretical investigations of formamide decomposition have been reported in the literature. In the present work, unimolecular decomposition of formamide in the electronic ground state was investigated by classical direct chemical dynamics simulations. The calculations were performed at three different energies using the density functional B3LYP/aug-cc-pVDZ level of electronic structure theory. The major dissociation products observed were NH3, CO, H2, HNCO, H2O, HCN, and HNC along with products of a few minor dissociation channels. Reactivity, atomic level mechanisms, and product branching ratios were investigated as a function of total energy. © 2018 the Owner Societies.