The crystal and molecular structure of (−)—Crinine (C16H17NO3)

(–)—Crinine, C₁₆H₁₇NO₃, is an alkaloid extracted from the bulbs of Pancratium maritimum L. (Amaryllidaceae). The compound crystallizes in the space group P2₁2₁2₁ with cell dimensions a = 6.040(1), b = 12.382(1), c = 17.861(2) Å, with Z = 4. The molecule has five rings and an OH group. The N-containing, five-membered ring and the D ring have envelope conformations. The A and B rings have distorted chair and half-chair conformations, respectively.     

Novel vic-dioxime ligand containing calix[4]pyrrole moiety: synthesis,characterization, anion binding studies and complexation with Ni(II)

A new vic-dioxime functionalized calix[4]pyrrole was synthesized from anti-chloroglyoxime and 4-aminophenyl-calix[4]pyrrole at room temperature. The Ni(II) complex has been prepared by reacting the ligand with NiCl₂·6H₂O in ethanol. These receptors were characterized by elemental analyses, ¹H and ¹³C NMR spectra, IR and mass spectra. Electrochemical properties of the ligand, and its Ni(II) complex were investigated in CH₂Cl₂ solution by cyclic voltammetry at 100 mV s^?1 scan rate. Anion-binding studies were carried out using UV–Vis, and ¹H NMR titrations, revealed that the Ni(II) complex exhibits selective recognition toward F^? over other anions. The selectivity for F^– among the halides is attributed mainly to the hydrogen-bond interaction of the receptor with F^–. Receptor showed colour change from red to brown in the presence of tetrabutylammonium fluoride (TBAF) with 1:2 stoichiometry.     

Charge localization increases chemical expansion in cerium-based oxides

In this work, we demonstrate the mechanism by which electronic charge localization increases the chemical expansion coefficient in two model systems, CeO(2-δ) and BaCeO(3-δ). Using Density Functional Theory calculations, we predict that this coefficient is increased by more than 70% when charge is fully localized, consistent with the observation that materials with a smaller degree of charge localization have smaller chemical expansion coefficients. This finding has important consequences for devising materials with smaller chemical expansion coefficients and for the reliability of the widely-used Shannon's ionic radii.     

Synthesis of some azacrown derivatives and fabrication of their nanofilms on the glassy carbon surface

The modification of N-phenyl-aza-15-crown-5 (PA15C5) and N-(4-aminophenyl)-aza-15-crown-5 (4APA15C5) on glassy carbon (GC) electrode was performed by the electrochemical oxidation of the corresponding azacrown derivatives in anhydrous acetonitrile media. The electrochemical behavior of the resulting modified GC electrode was investigated in the presence of electroactive redox probes and these results, together with the X-ray photoelectron spectroscopy (XPS) and reflection-absorption infrared spectroscopy were used to confirm the attachment of these molecules onto the GC surface. The ellipsometric thicknesses of PA15C5 and 4APA15C5 films at the GC surface was obtained around 9.28 ± 0.40 and 10.50 ± 1.10 nm, respectively. Azacrown modified nanoscale surfaces serve as alkali metal sensor specific for their cavity in the crown ring.     

Surface electronic structure transitions at high temperature on perovskite oxides: the case of strained La0.8Sr0.2CoO3 thin films

In-depth probing of the surface electronic structure on solid oxide fuel cell (SOFC) cathodes, considering the effects of high temperature, oxygen pressure, and material strain state, is essential toward advancing our understanding of the oxygen reduction activity on them. Here, we report the surface structure, chemical state, and electronic structure of a model transition metal perovskite oxide system, strained La(0.8)Sr(0.2)CoO(3) (LSC) thin films, as a function of temperature up to 450 °C in oxygen partial pressure of 10(-3) mbar. Both the tensile and the compressively strained LSC film surfaces transition from a semiconducting state with an energy gap of 0.8-1.5 eV at room temperature to a metallic-like state with no energy gap at 200-300 °C, as identified by in situ scanning tunneling spectroscopy. The tensile strained LSC surface exhibits a more enhanced electronic density of states (DOS) near the Fermi level following this transition, indicating a more highly active surface for electron transfer in oxygen reduction. The transition to the metallic-like state and the relatively more enhanced DOS on the tensile strained LSC at elevated temperatures result from the formation of oxygen vacancy defects, as supported by both our X-ray photoelectron spectroscopy measurements and density functional theory calculations. The reversibility of the semiconducting-to-metallic transitions of the electronic structure discovered here, coupled to the strain state and temperature, underscores the necessity of in situ investigations on SOFC cathode material surfaces.     

Catalysis and reaction mechanisms of N-formylation of amines using Fe(III)-exchanged sepiolite

This study presents a rapid, economical and “green” N-formylation of anilines with formic acid (FA) using Fe(III)-exchanged sepiolite (IES) as a catalyst. The IES exhibited excellent catalytic properties and the reactions were complete within 20.90 min to afford products with high yields. The adsorption mechanism of FA on the IES sample was studied by infrared (IR) spectroscopy at a temperature range of 120–400°C. The thermal desorption of pyridine was detected by the IR technique to estimate the acidity of IES. Lewis acid-bound pyridine bands at 1618–1631 cm^-1 and 1443–1445 cm^-1 were observed even after the IES sample was heated above 400°C.     

Performance of birnessite-type manganese oxide in the thermal-catalytic degradation of polyamide 6

Birnessite-type manganese oxide (BMO) was prepared by oxidation of Mn(NO₃)₂ with H₂O₂ in KOH solution. The nature and the extent of degradation of polyamide 6 (PA6) in the presence of samples were analysed by thermogravimetric analysis under static air atmosphere at several heating rates between 5 and 30 °C min^?1. The surface and structure of BMO were characterized using infrared (IR) spectroscopy, X-ray diffraction, and thermal analysis techniques. The acid sites of BMO were investigated by IR using pyridine as a molecular probe. The activation energy for degradation estimated by Kissinger method for PA6 and BMO/PA6 system containing 10 mass% of BMO was found to be 212 and 144 kJ mol^?1 under air, respectively. The catalytic activity observed in BMP catalyst was associated to a high lattice oxygen mobility.