Synthesis of 2- and 4-substituted 5,12-dihydroxy-6,11-dioxo-1-azanaphthacenes from 2-aminoquinizarine

The reaction of 2-aminoquinizarine with α,β-unsaturated carbonyl compounds in presence of 10N-hydrochloric acid gives 2- and 4-substituted 5,12-dihydroxy-6,11-dioxo-1-azanaphthacenes.     

Synthesis and characterization of titanates of the formula MTiO3 (M = Mn,Fe, Co,Ni and Cd) by co-precipitation of mixed metal oxalates

When divalent metal chloride solutions of Mn, Fe, Co, Ni and Cd were mixed with potassium titanyl oxalate solution, mixed metal oxalates were obtained in the case of Fe, Co and Ni at room temperature in the pH range 1.5–3. In the case of manganese, heating was found to be necessary to induce precipitation and complete precipitation occurred at 80 °C. Mixed cadmium and titanyl oxalate precipitation was complete at a pH of 3 at room temperature. Various physico-chemical techniques were employed to characterize the as-dried oxalate precursors and the final MTiO₃ oxide powders (M = Mn, Fe, Co, Ni and Cd) obtained on thermal decomposition. All these experimental results relating to the synthesis and characterizations of MTiO₃ oxides are presented in this paper. The results suggest that the reaction of potassium titanyl oxalate and metal chloride solutions may not lead to the formation of a single molecular precursor by direct salt elimination reaction in the pH range 1.5–3.     

Anion recognition by bisimidazolium and bisbenzimidazolium cholapods

Bile acid-based acyclic receptors bearing two imidazole and benzimidazole moieties have been synthesized. Anion binding studies using ¹H NMR revealed that imidazolium receptor exhibits high selectivity for chloride ion while benzimidazolium receptor showed selectivity for Y-shaped acetate ion through hydrogen bond interactions involving imidazolium C-2 and acetyl methylene hydrogens.     

Enhanced Four-Electron Selective Oxygen Reduction Reaction at Carbon-Nanotube-Supported Sulfonic-Acid-Functionalized Copper Phthalocyanine

In the present work, the oxygen reduction reaction (ORR) is explored in an acidic medium with two different catalytic supports (multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped multi-walled carbon nanotubes (NMWCNTs)) and two different catalysts (copper phthalocyanine (CuPc) and sulfonic acid functionalized CuPc (CuPc-SO₃⁻)). The composite, NMWCNTs-CuPc-SO₃⁻ exhibits high ORR activity (assessed based on the onset potential (0.57 V vs. reversible hydrogen electrode) and Tafel slope) in comparison to the other composites. Rotating ring disc electrode (RRDE) studies demonstrate a highly selective four-electron ORR (less than 2.5 % H₂O₂ formation) at the NMWCNTs-CuPc-SO₃⁻. The synergistic effect of the catalyst support (NMWCNTs) and sulfonic acid functionalization of the catalyst (in CuPc-SO₃⁻) increase the efficiency and selectivity of the ORR at the NMWCNTs-CuPc-SO₃⁻. The catalyst activity of NMWCNTs-CuPc-SO₃⁻ has been compared with many reported materials and found to be better than several catalysts. NMWCNTs-CuPc-SO₃⁻ shows high tolerance for methanol and very small deviation in the onset potential (10 mV) between the linear sweep voltammetry responses recorded before and after 3000 cyclic voltammetry cycles, demonstrating exceptional durability. The high durability is attributed to the stabilization of CuPc-SO₃⁻ by the additional coordination with nitrogen (Cu-N_x) present on the surface of NMWCNTs.     

Electronic,mechanical, phase transition,and thermo-physical properties of TMC (TM = V,Nb, and Ta): high pressure ab initio study

The structural, electronic, mechanical, phase transition, and thermo-physical properties of refractory carbides, viz. VC, NbC, and TaC have been computed in stable B1 and high pressure B2 phases by means of two different ab initio calculations using pseudo- and full-potential schemes. These materials have mixed covalent-, metallic-, and ionic-type bonding. The calculations of elastic constants show the mechanical stability of these materials in B1 phase only. The brittle nature and anisotropy is observed in these materials in B1 phase. Non-central forces are present in both the phases. Elastic wave velocities and Debye temperature have also been calculated. The present results on structural, phase transition, elastic, and other properties are in reasonably good agreement with the available experimental and theoretical data. The calculations in high pressure phase need experimental verification.     

Theoretical investigation of the alloxan–dialuric acid redox cycle

The redox cycle between alloxan, a mild oxidizing agent, and its reduction partner, dialuric acid, is investigated using density functional theory. It is found that the initial step is the one‐electron reduction of alloxan followed by protonation, yielding a stable neutral radical, AH^·. The radical can then accept another electron to form the dialuric acid anion. The formation of this anion is thermodynamically favored in both the gas phase and in solution. The radical may also undergo dimerization to alloxantin, followed by the transfer of a proton from one moiety to another, yielding alloxan and dialuric acid. This reduction is thermodynamically feasible in the gas phase, but not in aqueous solution. In the case of reduction of alloxan by glutathione at the physiological pH, computed redox potentials indicate that a two‐electron reduction is the favored course of reaction, yielding directly the dialuric acid anion, which then undergoes aerial oxidation to yield the superoxide radical. The redox cycling between alloxan and dialuric acid is responsible for the diabetogenic activity of alloxan, producing cytotoxic radicals on reoxidation of dialuric acid. © 2013 Wiley Periodicals, Inc.     

Radiation effect on temperature distribution in three-dimensional Couette flow with suction or injection

A theoretical analysis of three-dimensional Couette flow with radiation effect on temperature distribution has been analysed, when the injection of the fluid at the lower stationary plate is a transverse sinusoidal one and its corresponding removal by constant suction through the upper porous plate is in uniform motion. Due to this type of injection velocity, the flow becomes three-dimensional. The effect of Prandtl number, radiation parameter and injection parameter on rate of heat transfer has been examined by the help of graphs. The Prandtl number has a much greater effect on the temperature distribution than the injection or radiation parameter.     

Alpha-deuteron structure of 6Li as predicted by a separable-potential three-body model

Schroedinger's equation with separable n-p (³S₁) and $\text{n}\text{-α (}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}$ potentials solved to obtain a three-body model of the ⁶Li ground-state wave function. This model predicts the α-n-p binding energy of ⁶Li to be 4.67 MeV [Exp.: 4.53 MeV = 3.697 + 0.834 (Coulomb)], the asymptotic normalization constant of the d-α tail to be 2.39, and the amount of d+α component to be 65%. The ⁶Li→α+d vertex function is slightly more momentum dependent than present experiments suggest.