A green solid acid catalyst 12-tungstophosphoric acid H3[PW12O40] supported on g-C3N4 for synthesis of quinoxalines

Research on Chemical Intermediates - A green Keggin-type heteropoly-12-tungstophosphoric acid, (H3[PW12O40].12H2O) supported on graphitic carbon nitride g-C3N4 (HPW/g-C3N4-40), was developed for...     

Convenient Approaches towards the Synthesis of Novel Pyrano[2,3‐a]carbazoles

Previously not easily accessible pyrano[2,3‐a]carbazoles were synthesized in highly convergent syntheses avoiding multistep procedures from readily available 1‐hydroxycarbazoles. Substituted pyrano[2,3‐a]carbazoles were produced by three different methods by treatment of the 1‐hydroxycarbazoles with dimethyl acetylene dicarboxylate (DMAD) and triphenylphoshine, by reaction with ethyl 2‐methylacetoacetate in the presence of ZnCl₂/POCl₃, and by reaction with trifluoroacetic acid followed by Wittig reaction with (carbethoxymethylene) triphenylphosphorane. The article also highlights the optimization of reaction conditions and strategies to avoid formation of byproducts for all three types of reactions.     

A new methodology to recycle polyester from fabric blends with cellulose

Development of a simple process for separating cellulose and polyester from their mixed fabrics is indispensable for the recycling of waste mixed fabrics. The authors have developed an efficient two-step procedure that consists of an acid treatment and successive mechanical treatment of the mixed fabrics, or more specifically a 1-min static acid treatment of the mixed fabrics with 95 °C aqueous 10 N H₂SO₄ and successive mechanical beating in room-temperature water. The procedure was also found to be effective for the separation of regenerated cellulosic fabrics from their mixed fabrics with polyester. Cellulose was efficiently removed from polyester fabrics as a powder, with high recovery of both cellulose powder and polyester cloth.     

Heteropoly acid supported on activated natural clay-catalyzed synthesis of 3,4-dihydropyrimidinones/thiones through Biginelli reaction under solvent-free conditions

Dihydropyrimidinones/thiones (DHPM’s) have been prepared by one-pot condensation of methyl acetoacetate, aldehydes, urea/thiourea in the presence of heteropoly-11-tungsto-1-vanadophosphoric acid, H₄[PVW₁₁O₄₀]?·?32H₂O, (HPV) supported on activated natural clay (HPVAC) under solvent-free reaction condition have been proposed. The DHPM derivatives were identified through elemental analysis and melting point measurements and characterized by FT-IR, ¹H-NMR, ¹³C-NMR spectroscopic methods.     

A Highly Conjugated Benzimidazole Carbene‐Based Ruthenium Sensitizer for Dye‐Sensitized Solar Cells

A new type of carbene‐based ruthenium sensitizer, CB104, with a highly conjugated ancillary ligand, diphenylvinylthiophene‐substituted benzimidazolepyridine, was designed and developed for dye‐sensitized solar cell applications. The influence of the thiophene antenna on the performance of the cell anchored with CB104 was investigated. Compared with the dye CBTR, the conjugated thiophene in the ancillary ligand of CB104 enhanced the molar extinction coefficient of the intraligand π–π* transition and the intensity of the lower energy metal‐to‐ligand charge‐transfer band. However, the incident photon‐to‐current conversion efficiency spectrum of the cell anchored with CB104 (0.15 mM ) showed a maximum of 63 % at 420 nm. The cell sensitized with the dye CB104 attained a power conversion efficiency of 7.30 %, which was lower than that of the cell with nonconjugated sensitizer CBTR (8.92 %) under the same fabrication conditions. The variation in the performance of these two dyes demonstrated that elongating the conjugated light‐harvesting antenna resulted in the reduction of short‐circuit photocurrent density, which might have been due to the aggregation of dye molecules. In the presence of a coabsorbate, chenodeoxycholic acid, the CB104‐sensitized cell exhibited an enhanced photocurrent density and achieved a photovoltaic efficiency of 8.36 %.     

Dielectric and conduction mechanism studies of Ni doped LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> synthesized by solution combustion method

In the present work, structural, morphological, dielectrical, and electrochemical properties of LiNi_xMn_(2-x)O₄ (where x?=?0, 0.1,0.3, 0.5 mol%) prepared by solution combustion method were reported. X-ray diffraction studies confirmed the formation of cubic spinel structure without any impurity phases. Scanning electron micrographs revealed grains of micrometer range with a spherical like morphology and narrow size distribution. Dielectric parameters such as dielectric constant, dielectric loss, impedance, and electrical modulus were found to depend on temperature, frequency, and dopant concentration. AC conductivity was found to increase with increase in temperature exhibiting negative temperature co-efficient of resistance (NTCR) property in the material. Complex impedance and electrical modulus studies revealed the existence of temperature-dependent electrical relaxation in the material. The Correlated Barrier Hopping (CBH) model of conduction mechanism was confirmed by the decrease in s parameter with increase in temperature. Charge-discharge studies revealed the stabilization of spinel lattice by Ni ions, contributing to better capacity retention.     

Multi spectroscopic and computational investigations on the electronic structure of oxyclozanide

The present work contributes to a combined theoretical and experimental investigation on oxyclozanide. The experimental vibrational spectra were characterized by Fourier transform infrared (4000-400 cm^?1), Fourier transform Raman (4000-400 cm^?1), ¹H and ¹³C NMR were recorded in Deuterated methanol, UV–Vis (200–400 nm) techniques and theoretical optimized molecular geometry, harmonic vibrational spectra, magnetic spectra, and electronic spectra was calculated by Density Functional Theory (DFT) employed with B3LYP/6-311++G(d,p) basis set and compared with experimental data. The highest occupied molecular orbital - lowest unoccupied molecular orbital (HOMO-LUMO) energy was also calculated for the titled compound. The intermolecular interactions have been addressed through Hirshfeld surface analysis. In addition, Natural bond orbital (NBO) analyses of the title compound were performed to evaluate the suitable reactivity site and chemical stabilization behavior, Mulliken atomic charge distribution, and molecular electrostatic potential energy surfaces, were calculated to get a better insight into the structure of oxyclozanide. The experimental and theoretical findings suggest an excellent correlation to confirm the structure of oxyclozanide.     

One-step hydrothermal synthesis of marigold flower-like nanostructured MoS<Subscript>2</Subscript> as a counter electrode for dye-sensitized solar cells

MoS₂ thin films with marigold flower-like nanostructures were grown on conductive fluorine-doped tin oxide (FTO) substrates through a one-step hydrothermal synthesis for their application as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Different MoS₂ thin film samples (A–D) were grown on FTO slides using different concentrations of precursors (sodium molybdate and thioacetamide), while keeping the Mo/S molar ratio constant (1:4.6), in all samples. The effect of varying precursor concentrations (3.2–12.6 mM on MoS₂ basis) on the structure of the nanostructured thin films and their performance as DSSC-CEs was investigated. Scanning electron microscopy revealed a material with an infolded petal-like morphology. With increasing precursor concentration, the petal-like structures tended to form bunched nanostructures (100–300 nm) resembling marigold flowers. X-ray diffraction analysis, X-ray photoelectron, and Raman spectroscopy studies showed that the thin films were composed of hexagonal MoS₂ with good crystallinity. Hall effect measurements revealed MoS₂ to be a p-type semiconductor with a carrier mobility of 219.80 cm² V^?1 s^?1 at room temperature. The electrochemical properties of the thin films were examined using cyclic voltammetry and electrochemical impedance spectroscopy. The marigold flower-like MoS₂ thin films showed excellent electrocatalytic activity towards the I¯/I₃¯ reaction and low charge transfer resistance (R_ct) values of 14.77 Ω cm^?1, which was close to that of Pt electrode (12.30 Ω cm^?1). The maximum power conversion efficiency obtained with MoS₂ CE-based DSSCs was 6.32%, which was comparable to a Pt CE-based DSSC (6.38%) under one sun illumination. Similarly, the maximum incident photon-to-charge carrier efficiency exhibited by MoS₂ CE-based DSSCs was 65.84%, which was also comparable to a Pt CE-based DSSC (68.38%). The study demonstrated that the marigold flower-like nanostructured MoS₂ films are a promising alternative to the conventional Pt-based CEs in DSSCs.

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New triruthenium clusters as photoinduced DNA-binding and cleaving agents

1-Hydroxybenzotriazole and 1-hydroxypyridine-2-thione were incorporated as ligands with the cluster Ru3(CO)10 (NCMe)2 to give [(mu-H)Ru3(CO)10(mu2-2,3-eta2-NNN(O)C6 H4)] and [(mu-H)Ru3(CO)9(mu2-eta1 : eta2-C5H4N(O)S)], respectively. Irradiation of these two new triruthenium metal clusters individually with 350 nm UV light in a phosphate buffer (pH 6.0) containing form I DNA resulted in single-strand cleavage. Cluster [(mu-H)Ru3(CO)10(mu2-2,3--eta2-NNN (O)C6H4)] was also found to bind to calf thymus DNA upon UV irradiation.     

Rainbow beads: a color coding method to facilitate high-throughput screening and optimization of one-bead one-compound combinatorial libraries

We have developed a new color-encoding method that facilitates high-throughput screening of one-bead one-compound (OBOC) combinatorial libraries. Polymer beads displaying chemical compounds or families of compounds are stained with oil-based organic dyes that are used as coding tags. The color dyes do not affect cell binding to the compounds displayed on the surface of the beads. We have applied such rainbow beads in a multiplex manner to discover and profile ligands against cell surface receptors. In the first application, a series of OBOC libraries with different scaffolds or motifs are each color-coded; small samples of each library are then combined and screened concurrently against live cells for cell attachment. Preferred libraries can be rapidly identified and selected for subsequent large-scale screenings for cell surface binding ligands. In a second application, beads with a series of peptide analogues (e.g., alanine scan) are color-coded, combined, and tested for binding against a specific cell line in a single-tissue culture well; the critical residues required for binding can be easily determined. In a third application, ligands reacting against a series of integrins are color-coded and used as a readily applied research tool to determine the integrin profile of any cell type. One major advantage of this straightforward and yet powerful method is that only an ordinary inverted microscope is needed for the analysis, instead of sophisticated (and expensive) fluorescent microscopes or flow cytometers.