Mononuclear gallium (III) complexes based on salicylaldoximes: Theoretical study of structures, topological and NBO analysis of hydrogen bonding interactions involving O–H···O bonds

AbstractThe intramolecular O–H···O resonance-assisted hydrogen bonds in crystal structures of mononuclear gallium (III) complexes with salicylaldoximes are investigated. The molecular structures of these compounds were taken from X-ray crystal structures and further used to perform theoretical calculations at B3LYP/6-311G(d,p) level. The geometrical parameters of O–H···O intramolecular H-bonds were analyzed. The natural bond orbital theory (NBO) and the atoms in molecules theory (AIM) were also applied to get a more precise insight into the nature of such H-bond interactions. The bond critical points and the ring critical points were determined and their characteristics were also analyzed

Microwave assisted synthesis of La-1 (-) xCaxMnO3 (x=0, 0.2 and 0.4): Structural and capacitance properties

The effect of calcium incorporation on the physicochemical and electrochemical properties of the LaMnO3 (LM) perovskites was studied via several techniques. Moreover, a new microwave assisted method was used to synthesize La(1-x)Ca(,)M(x)nO(3)(LCM) perovskites with various calcium content (x = 0.2 and 0.4). Then, the physicochemical properties of the materials such as crystal structure, particle size, surface area, reducibility and band gap energy were investigated by X-ray Diffraction (XRD), High resolution Scanning and Transmission Electron Microscope (HR-SEM and HR-TEM), BET analysis, Temperature-programmed Reduction (TPR) and UV-visible Diffuse Reflectance Spectroscopy (UV-VIS DRS). The increase in partial concentration of calcium resulted in a high specific surface area, larger particle size and an enhanced reducibility along with an increase in the band gap energy. In addition, cyclic voltammetry was applied to LM and LCM perovskites to determine the effect of calcium incorporation on the capacitance of the electrochemical cell. It showed that the capacitance decreases with the amount of Ca2+ incorporated into the LM structure. This effect is linked to the formation of Mn4+, which hinders the electron transfer in the structure. The decline in the charge transfer is revealed by the specific capacitance. Finally, our findings showed that the microwave assisted method provides a green, efficient and time-saving route for perovskite synthesis and the calcium incorporation induces a negative effect on the capacitance properties of the LM perovskites

Mesoporous ZnCr₂O₄ Nanocatalyst with High Specific Surface Area for Facile Synthesis of Flavonoid Derivatives

ZnCr2O4 nanoparticles with a high specific surface area have been fabricated using a hydrothermal synthetic process and were used as an effective catalyst to synthesize flavonoid derivatives. The textural and structural properties of the spinel were studied by X-ray diffraction (XRD), Field Emission scanning electron microscope (FE-SEM), nitrogen sorption techniques, and Fourier transform infrared spectroscopy (FT-IR). XRD confirmed the formation of cubic Zinc Chromite spinel with a small crystallite size of 5.04 nm. While Transmission Electron Microscopy (TEM) illustrated the particle size of ∼8, 10, and 16 nm. Textural analysis by N2 sorption revealed a mesoporous system with a high specific surface of 215 m2/g for ZnCr2O4. Moreover, all desired flavonoids were obtained in high yields under solvent-free conditions with the aid of the ZnCr2O4 catalyst. Structures of all flavonoid derivatives were confirmed by 1H-NMR, 13C-NMR, FT-IR, and their melting points.</p