Selective hydrogenation of cinnamaldehyde catalyzed by palladium nanoparticles immobilized on ionic liquids modified-silica gel

In this paper, preparations of supported Pd catalysts by immobilization of Pd(OAc)₂ on silica gel that was modified by N-3-(-3-triethoxysilylepropyl)-3-methylimidazolium based ionic liquids ([(TESP)MIm][X], X = Cl⁻, ${\text{NO}}_3^{-}$, ${\text{BF}}_4^{-}$, and ${\text{PF}}_6^{-}$), and together with their catalytic applications for hydrogenation of cinnamaldehyde, were investigated. Depending on the ionic liquid involved, palladium can exist in the form as either palladium carbene complex (X = Cl⁻) or palladium nanoparticles with size less than 10 nm ($\text{X}={\text{NO}}_3^{-}$, ${\text{BF}}_4^{-}$, and ${\text{PF}}_6^{-}$), which, in turn, lead to different catalytic activities in respect to hydrogenation of cinnamaldehyde. Supported Pd nanoparticles were demonstrated to be high active and reusable catalysts for selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde, due to the stabilization effect of ionic liquids. Keeping the yield of product as 100%, they can be reused for nine times with neither Pd leaching nor activity loss, and offer the value of TON as high as nearly 500,000.     

Synthesis of a new ion imprinted polymer material for separation and preconcentration of traces of uranyl ions

Uranyl ion imprinted polymers (IIPs) were synthesized by formation of ternary or binary complexes of uranyl ion $({\text{UO}}_2^{2+})$ with Piroxicam (Pir) and 4-vinylpyridine (VP) as chelating agent following copolymerizing with styrene as functional monomer and divinylbenzene (DVB) or ethyleneglycoldimethyl methacrylate (EGDMA) as cross-linking monomer using 2,2′-azobisisobutyronitrile as initiator. Control polymers (CPs) were prepared under identical conditions without the use of uranyl imprint ion. The synthesized polymers were characterized by IR spectroscopy, X-ray diffraction and thermal analysis techniques. Of the several polymers synthesized, the imprinted polymer formed with ternary complex of ${\text{UO}}_2^{2+}\text{-Pir}''–''\text{VP}$ (1:2:2;IIP1) showed quantitative enrichment of uranyl ion from aqueous solution. Then various parameters that affect the preconcentration were optimized in both batch and column methods. The percent enrichment and retention capacity of IIP1 for ${\text{UO}}_2^{2+}$ was found to be 98% and 38.58 mg g⁻¹, respectively. The proposed IIP1 was tested for preconcentration of uranyl ion from ground water and sea water samples.     

Ferromagnetic interactions in a bis(μ-end-on azido)cobalt(II) linear trimer

A linear trinuclear Co(II) compound, [Co₃(μ_1,1-N₃)₄(N₃)₂(H₂O)₂(bpbp)₂] · 2H₂O (1, bpbp = 3,3′-bis-Dimethylamino-1,1′-pyridine-2,6-diyl-bispropenone), is reported. The central Co(II) ion is bridged to Co(II) ions on both sides by four end-on azide (${\mathrm{\mu }}_{1\text{,}1}\text{-}{\text{N}}_3^{-}$) ligands resulting in a centrosymmetric trimer with adjacent Co?Co distance of 3.233 Å. Each Co(II) ion possesses distorted octahedral geometry, the central one is coordinated by two aqua ligands and four ${\mathrm{\mu }}_{1\text{,}1}\text{-}{\text{N}}_3^{-}$ nitrogen atoms and each terminal Co(II) is coordinated by two ${\mathrm{\mu }}_{1\text{,}1}\text{-}{\text{N}}_3^{-}$ nitrogen atoms, one terminal ${\text{N}}_3^{-}$ nitrogen atom and capped by terminal tridentate bpbp ligand. Variable temperature magnetic studies indicate ferromagnetic coupling between adjacent Co(II) ions within the trimer.