Polyhedron 

About: Polyhedron is an academic journal. The journal publishes majorly in the area(s): Ligand & Crystal structure. It has an ISSN identifier of 0277-5387. Over the lifetime, 19190 publication(s) have been published receiving 304079 citation(s). The journal is also known as: 3-polytope & polyhedra.

The use of new ionic liquids in two-phase catalytic hydrogenation reaction by rhodium complexes

Abstract: The reaction of 1-n-butyl-3-methylimidazolium chloride (BMIC) with sodium tetrafluoroborate or sodium hexafluorophosphate produced the room temperature-, air- and water-stable molten salts (BMI+)(BF4−) (1) and (BMI+)(PF6−) (2), respectively, in almost quantitative yield. The rhodium complexes RhCl(PPh3)3 and [Rh(cod)2][BF4] are completely soluble in these ionic liquids and they are able to catalyse the hydrogenation of cyclohexene at 10 atm and 25°C in a typical two-phase catalysis with turnovers up to 6000.

Silasesquioxanes as ligands in inorganic and organometallic chemistry

Abstract: Silasesquioxanes are an interesting class of ligands for both main group and transition-metal elements. A variety of coordination environments can be supported by silasesquioxane ligands, and it is now possible to prepare metallasilsesquioxanes containing practically any stable element from Groups 1015. This article surveys the synthesis, characterization, and reactivity of silasesquioxane ligands. Structure, bonding and structural dynamics of both silasesquioxanes and metallasilasesquioxanes are also discussed. The chemistry of silasesquioxanes and metallasilasesquioxanes can provide important insights into the chemistry of silica and silica-supported transition-metal catalysts. The uniqueness of silasesquioxanes as models for silica is discussed and several systems which provide molecular-level insights into the surface chemistry of silica and silica-supported catalysts are discussed.

Enhanced photocatalytic activity of nanostructured titanium dioxide/polyaniline hybrid photocatalysts

Abstract: An organo-inorganic photocatalytic nanocomposite material based on conjugated polymer, polyaniline (PANI) with titanium dioxide (TiO2) nanoparticles has been developed by performing in situ chemical oxidative polymerization of aniline with ammonium persulfate (APS) oxidant in the presence of hydrothermally synthesized TiO2 nanoparticles. The structural and morphological properties of TiO2/PANI nanocomposites were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), respectively. The TEM results of the TiO2/PANI nanocomposites showed that TiO2 nanoparticles of 5–10 nm of sizes are dispersed in the PANI matrix. FT-IR spectra show that the TiO2/PANI nanocomposites are almost identical to the structure of PANI alone. The photocatalytic activities of the nanocomposites were evaluated by the photocatalytic degradation of Rhodamine B (RhB), Methylene Blue (MB) and phenol in the presence of UV-light irradiation. The composite catalysts exhibited higher photocatalytic activity for the degradation of organic pollutants than unmodified TiO2 nanoparticles, which is due to sensitizing effect of PANI.

Synthesis, structures and fluorescence of nickel, zinc and cadmium complexes with the N,N,O-tridentate Schiff base N-2-pyridylmethylidene-2-hydroxy-phenylamine

Abstract: Mono-, tri- and dinuclear neutral complexes [Ni(HL)(L)] · (ClO4) · 0.16(H2O) (1), [ZnLZn(OOCCH3)4ZnL] (2) and [Cd2L2(OCH3CO)2(H2O)2] (3) have been obtained from the reaction between the potentially tridentate N,N,O-donor Schiff base ligand HL, where HL = N-2-pyridylmethylidene-2-hydroxy-phenylamine with nickel, zinc or cadmium salts, respectively. The ligand has been prepared by 1:1 condensation of pyridine-2-carboxaldehyde and 2-aminophenol. The ligand and metal complexes were characterised by elemental analysis, spectroscopic studies such as IR, UV–Vis, 1H NMR, fluorescence, electrochemical and magnetic susceptibility measurement. The structures of the three complexes have been determined by single-crystal X-ray diffraction. The nickel ions in 1 show a distorted mer-octahedral geometry. In 2, the terminal zinc ions have coordination geometry midway between square pyramidal and trigonal bipyramidal, whilst the central zinc ion has slightly distorted octahedral geometry. The trinuclear unit is held together by bridging deprotonated phenolic oxygen atoms from the Schiff base and acetate groups. In 3, two monocapped-octahedron cadmium ions are held together by μ2-diphenoxo bridges. Among the three synthesised complexes, 1 is nonfluorescent while the other two can serve as potential photoactive materials as indicated from their characteristic fluorescence properties.