A new sol-gel synthesis of Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> oxide and its electrochemical behavior in alkaline medium

In this investigation, Mn₃O₄ spinel-type oxide was synthesized at low temperature using the Pechini process. We employed a sol-gel route, in which a solution of Mn(II) in a mixture of citric acid and ethylene glycol was heated to form a polymeric precursor, followed by annealing at lower temperature. The oxide obtained was identified by X-ray diffraction, scanning electron spectroscopy, and Raman spectroscopy. The results revealed that the formation of Mn₃O₄ hausmannite structure with a minor secondary phase of MnSO₄ occurred at or above 280 °C. The sample powder consisted of fine grains with homogeneous morphology and an average size close to 1 μm was obtained. This new preparation procedure yielded an electrode oxide which appears to be a promising cathode material for fuel cells and metal-air batteries.     

Synthesis of New (4‐Acetonylidene‐2,6,8,9‐tetramethyl‐7H‐imidazo[1,5,4‐e,f][1,5]benzodiazepine) Derivatives

Imidazobenzodiazepine derivatives were obtained by cyclization of the condensation products 7‐amino‐2,5,6‐trimethylbenzimidazole with acetylacetone and ethyl acetoacetate. By careful examination of spectroscopic data and the open‐chain intermediate isolation, we have identified the formed compound structure.     

2H QUOSY 2D-NMR Experiments in Weakly Aligning Systems: From the Conventional to the Ultrafast Approach

We describe three anisotropic ultrafast (UF) QUadrupolar Ordered SpectroscopY (QUOSY) 2D-NMR experiments (referred to as ADUF 2D NMR spectroscopy) designed for recording the ²H homonuclear 2D spectra of weakly aligned (deuterated) solutes in sub-second experiment times. These new ADUF 2D experiments derive from the Q-COSY, Q-resolved and Q-DQ 2D pulse sequences (J. Am. Chem. Soc. 1999 , 121, 5249) and allow the correlation between the two components of each quadrupolar doublet, and then their assignment on the basis of ²H chemical shifts. The UF 2D pulse sequences are analyzed by using the Cartesian spin-operator formalism for spin I=1 nuclei with a small quadrupolar moment. The optimal experimental/practical conditions as well as the resolution, sensitivity and quantification issues of these ADUF 2D experiments are discussed on comparison to their conventional 2D counterparts and their analytical potentialities. Illustrative ADUF 2D experiments using deuterated achiral/prochiral/chiral solutes in poly-γ-benzyl-L-glutamate based chiral liquid crystals are presented, as well as the first examples of natural abundance deuterium (ANADUF) 2D spectrum using 14.1 T magnetic field and a basic gradient unit (53 G.cm⁻¹) in oriented solvents.     

Effect of Co substitution for Fe in Sr2FeMoO6 on electrocatalytic properties for oxygen reduction in alkaline medium

Double perovskites Sr₂Fe_1???x Co _x MoO₆ (x?=?0, 0.25, 0.5, 0.75 and 1) have been investigated as cathode material for oxygen reduction reaction (ORR) in 0.5 M NaOH at 25 °C using the rotating disk electrode. The electrocatalytic powders were prepared by a solid-state process and characterised by X-Ray powder diffraction, scanning electron microscopy and infrared spectroscopy. The electrochemical techniques considered are linear voltammetry, steady-state polarization and impedance spectroscopy. The electrocatalysts Sr₂Fe_1???x Co _x MoO₆/C consisting of the double perovskite oxides and carbon (Vulcan XC-72) were mixed and spread out into a thin layer on a glassy carbon substrate. The electrocatalytic activity was strongly influenced by the Co substitution at room temperature. The relation between catalytic performance and the degree of Co content was examined. The Co-containing catalysts exhibited lower activity attributed to their high resistivity, and the highest activity toward oxygen reduction was observed for Sr₂CoMoO₆.     

Synthesis and characterization of new polyamides based on Diphenylaminoisosorbide

New aromatic polyamides were synthesized by the microwave‐assisted polycondensation of an optically active isosorbide‐derived diamine with different diacyl chlorides in the presence of a small amount of N‐methylpyrrolidinone. Polymers with inherent viscosities between 0.22 and 0.73 dL/g were obtained corresponding to molecular weights up to 140,000 g/mol. With interfacial polymerization or the Higashi method, lower molecular weight polymers were obtained with inherent viscosities in the range of 0.04–0.36 dL/g. Differential scanning calorimetry measurements clearly demonstrated the high thermal stability of these polymers (mp = 180–300 °C) and the absence of decomposition. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6480–6491, 2005     

New materials derivatives of tetrathiapentalene functionalized by amide groups: Synthesis,characterization, and electrical study

A new series of bis-fused tetrathiafulvalene containing functional groups was synthesized. The synthesis was carried out by using routes involving cross coupling, reduction, and oxidation reactions. The identity of these new donors is confirmed by ¹ Wudl, F.; Smith, G. M.; Hufnagel, E. J. J. Chem. Soc. Chem. Commun. 1970, 21, 1453-1454.[Crossref] , [Google Scholar] H NMR spectroscopy, mass spectrometry, and elemental analysis. We have used the cyclic voltammetry in order to determine the character π-donors of these molecules and to verify the reversibility of the redox process involved. Molecular orbital diagram has been calculated using density-functional calculations. Charge transfer complexes with tetracyanoquinodimethane (TNQ) were prepared by chemical redox reactions.     

Potassium Fluoride on Alumina: An Easy Synthesis of 4-Alkylidene-2-Thione-1,3-Oxathiolanes from α-Acetylenic Alcohols

α-acetylenic alcohols and carbon disulfide in the presence on potassium fluoride on alumina without solvent give selectively 4-alkylidene-2-thione- 1,3-oxathiolanes     

π-Stacked ortho-Palladated Bipyridine Complexes Exhibiting Unusual Liquid Crystalline Behavior

A columnar structure with lamellar morphology in the liquid crystalline state is displayed by the palladium complex salt 1 , which is synthesized from nonmesogenic ligands.     

Fine-Tuning the Electronic Properties of Binuclear Bis(terpyridyl)ruthenium(II) Complexes

Vastly improved photophysical properties of terminal Ru^II terpyridine-based chromophores is achieved by insertion of an ethynylene group between the terpyridine ligand and a covalently linked aromatic nucleus. In the case where the aromatic nucleus possesses vacant coordination sites, as shown in 1 , complexation of certain cations (e. g., Zn²⁺, Cd²⁺, or Ba²⁺) at the central unit gives a further improvement in the photoproperties due to a better blending of the respective LUMO levels.