C3(SINGLE BOND)Mα Bond contribution to polarizability tensor and 3J(C1Mα) NMR coupling constant in 1-X-3-M-bicyclo[1.1.1]pentanes

In the present work, the relationship between the large substituent effects on ³J(C₁H) in 1-X-3-M-bicyclo[1.1.1]pentanes, I , and the polarizability of the bridgehead C₃(SINGLE BOND)M_α bond is investigated. The existence of such a relationship is suggested by the finding that the effect of an electronegative substituent X on ³J(C₁M_α) couplings in I (M=H) is due to a distortion of the C₃(SINGLE BOND)H bond toward the C₁ center, which enhances the Fermi contact interaction. If such distortion originates in an electrostatic effect, then in other members of this series it can be expected that the substituent effects on ³J(C₁M_α) couplings should depend strongly on the C₃(SINGLE BOND)M_α bond polarizability. Two approaches are followed. First, the ab initio CLOPPA-IPPP method is applied to study the C₃(SINGLE BOND)M_α bond contribution to the molecular static polarizability tensor in I (M=H, F, CH₃). Such bond polarizabilities are found to follow the same trend as calculated as well as experimentally determined substituent effects on ³J(C₁M_α) couplings, which were measured as part of this work in I [X=H, Cl; M=F, CH₃ and X=OCH₃; M=Sn(CH₃)₃]. Second, ³J(C₁M_α) couplings (M=H, CH₃) are calculated at an ab initio level for X=H, F, and they are compared with those obtained in the parent compound (X=H) if the calculation is carried out in the presence of an inhomogeneous electric field. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 181–188, 1998     

Two new dibenzobicyclic penta- and hexacoordinated tin compounds

Two new dibenzobicyclic penta- andhexacoordinated tin compounds ( 1–2 ) were prepared, derived from bis(2-hydroxy-3,5-di-tert-butyl-phenol)imine and dichloro-dimethylstannane and trichloro-n-butylstannane, respectively. Each compound is an example of two different coordination forms of the ligand. The crystalline complexes have been characterized by magnetic moment, infrared and mass spectrometry, elemental analysis, and X-ray diffraction studies. Compound 1 crystallized in the monoclinic system, space group P2₁/n; it contains a five-coordinated trigonal bipyramidal tin atom with methyl groups in equatorial positions and a planar dibenzobicyclic ring. It is a paramagnetic compound (μ_eff = 1.59 μ_B) due to the radical dianion nature of the ligand. Compound 2 crystallized also in the monoclinic system, space group P2₁/c; it contains a six-coordinated tin atom with an octahedral geometry; the dibenzobicyclic ring is planar, and the chlorine atoms are in trans positions. It is diamagnetic with a delocalized monoanion structure of the ligand. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:321–326, 1998     

Cobalt(II), nickel(II) and zinc(II) coordination compounds derived from aromatic amines

The structural and spectroscopic characterization of coordination compounds of four aromatic amines derived from benzimidazole, 2-aminobenzimidazole (L1), 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2), 2-(2-aminophenyl)-1H-benzimidazole (L3) and 6,6-dimethyl-5H-benzimidazolyl[1,2-c]quinazoline (L4) are reported. Cobalt(II) [Co(L1)₂(CH₃COO)₂] (1) and nickel(II) [Ni(L1)₂(CH₃COO)₂] (2) acetate coordination compounds of L1 are discussed. The synthesis and the X-ray crystal structure of the new 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2) is informed, together with its cobalt(II) [Co(L2)₂Cl₂] (3), [Co(L2)₂Br₂] (4) and zinc(II) [Co(L2)₂Cl₂] (5), [Zn(L2)₂Br₂] (6) coordination compounds. In these compounds the imidazolic nitrogen is coordinated to the metal center, while the ArNH₂ and the S-methylcarbodithioate groups do not participate as coordination sites. A co-crystal of L1 and L2 is analyzed. Structural analyses of the coordination compounds of L3 showed that this ligand behaves as a bidentate ligand through the aniline and the imidazole groups forming six membered rings in the cobalt(II) [Co(L3)Cl₂] (7) and zinc(II) [Zn(L3)Cl₂] (8) compounds, as well as the nickel(II) nitrate [Ni(L3)₂(H₂O)₂](NO₃)₂ (9). The quinazoline L4 was produced by insertion of one acetone molecule and water elimination in L3, its X-ray crystal diffraction analysis, as well as that of its zinc(II) coordination compound [Zn(L4)₂Cl₂] (10), are discussed.     

Internal Structure and Magnetic Properties in Cobalt Ferrite Nanoparticles: Influence of the Synthesis Method

The design of novel nanostructured magnetic materials requires a good understanding of the variation in the magnetic properties due to different synthesis conditions. In this work, four different procedures for fabricating Co‐ferrite nanoparticles with similar sizes between 7 and 10 nm are compared by studying their structural and magnetic properties. Non‐aqueous methods based on the thermal decomposition of metal acetylacetonates at high temperatures, either with or without surfactants, provide highly crystalline nanoparticles with large saturation magnetization values and a coherent reversal of the magnetic moment. However, variations in the density of defects and in the shape of the nanocrystals determine the distribution of switching fields and the effective magnetic anisotropy, which reaches up to ≈1 × 10⁷ erg cm^?3 for oleic acid‐capped 9 nm nanoparticles. It is shown that the saturation magnetization values for nanoparticles produced by different methods are in the range between 49 and 95 emu g^?1 due to differences in the stoichiometry, in the cation occupancy, in the magnetic disorder and in the spin canting of the magnetic sub‐lattices, the latter evaluated by in‐field Mössbauer spectroscopy.     

Lacunar Keggin Heteropolyacid Salts: Soluble,Solid and Solid-Supported Catalysts

Polyoxometalates are an important class of environmentally friendly catalysts. The Keggin heteropolyacids containing tungsten or molybdenum addenda atoms have received great attention because they have attractive acid and redox properties, which may be easily tunable through changes in their composition and structure. The replacement of their protons by large radium cations makes insoluble the Keggin heteropolyacids and increases their surface area. On the other hand, the removal of tungsten or molybdenum atoms from the Keggin heteropolyanion generates vacancies, which can activate different organic substrates. Therefore, solid lacunar heteropolyacid salts are potentially active catalysts and selective in a plethora of reactions. These catalysts are used either in homo- or heterogeneous conditions. In this review, we wish would highlight recent advances achieved in the chemistry of lacunar Keggin heteropolyacids. We describe their use as solid, soluble or solid-supported catalysts in reactions of oxidation of alcohols and olefins, oxidative desulfurization and acid-catalyzed reactions such as acetalization, esterification, and transesterification.     

Integration Operators in Average Radial Integrability Spaces of Analytic Functions

Mediterranean Journal of Mathematics - The original article has been published inadvertently with errors in page number 2.     

Polyol-assisted coprecipitation synthesis of BiOI photocatalyst and its activity to remove NOx

Research on Chemical Intermediates - BiOI samples were synthesized by coprecipitation method in glycerol medium at 100 °C followed by a thermal treatment of the precursor powders at...     

Simultaneous in situ generation of hydrogen peroxide and Fenton reaction over Pd-Fe catalysts

High mineralization degree of organic compounds can be achieved by a novel environmentally-friendly full heterogeneous Pd-Fe catalytic system, which involves in situ generation of hydrogen peroxide from formic acid and oxygen, and oxidation of organic compounds by Fenton process in a one-pot reaction.     

Hypervalent triphenyl and diphenyl tin coordination compounds derived from 2-(1H-benzimidazol-2-yl)phenol

Reactions of 2-(1H-benzimidazol-2-yl)phenol (1) and SnPh₃Cl, SnPh₂Cl₂ and SnCl₄ were investigated. One tetracoordinated triphenyltin(IV) compound: triphenyltin-2-(1H-benzimidazol-2-yl)phenolate] (3) and its adducts: [O → Sn] dimethylsulfoxide triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (4), [O → Sn] aqua triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (5) [O → Sn] ethanol triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (6), [N → Sn] pyridine triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (7), where 1 acts as a monodentate ligand bound through the phenol oxygen, were obtained. In the pentacoordinated compounds 4-7, the tin atom has tbp geometry. The three phenyl groups are in equatorial positions, whereas the benzimidazole and the Lewis base are in apical positions. Two hexacoordinated tin compounds: diphenyltin-bis[2-(1H-benzimidazol-2-yl-κN)phenolate-κO] (8), dichlorotin-bis[2-(1H-benzimidazol-2-yl-κN)phenolate-κO] (9) bearing two bidentate ligands are reported. The coplanar ligands in 8 and 9 form six membered rings by oxygen and nitrogen coordination. The tin geometry is all-trans octahedral. In 8 the two phenyl groups, and in 9 the two chlorine atoms are perpendicular to the plane of the ligands. Compounds were identified in solution mainly by ¹H, ¹³C and ¹¹⁹Sn NMR and in the solid state by X-ray diffraction analysis.