Ligand substitution and electronic structure studies of bis(phosphine)cobalt cyclooctadiene precatalysts for alkene hydrogenation

Diene self-exchange reactions of the 17-electron, formally cobalt(0) cyclooctadienyl precatalyst, (R,R)-(iPrDuPhos)Co(COD) (P2CoCOD, (R,R)-iPrDuPhos = 1,2-bis((2R,5R)-2,5-diisopropylphospholano)benzene, COD = 1,5-cyclooctadiene) were studied using natural abundance and deuterated 1,5-cyclooctadiene. Exchange of free and coordinated diene was observed at ambient temperature in benzene-d6 solution and kinetic studies support a dissociative process. Both neutral P2CoCOD and the 16-electron, cationic cobalt(I) complex, [(R,R)-(iPrDuPhos)Co(COD)][BArF4] (BArF4 = B[(3,5-(CF3)2)C6H3]4) underwent instantaneous displacement of the 1,5-cyclooctadiene ligand by carbon monoxide and generated the corresponding carbonyl derivatives. The solid-state parameters, DFT-computed Mulliken spin density and analysis of molecular orbitals suggest an alternative description of P2CoCOD as low-spin cobalt(II) with the 1,5-cyclooctadiene acting as a LX2-type ligand. This view of the electronic structure provides insight into the nature of the ligand substitution process and the remarkable stability of the neutral cobalt complexes toward protic solvents observed during catalytic alkene hydrogenation.

Physicochemical colourants effects on polymeric composites printing toner

Purpose – This paper aims to report on production of the colour digital printing toners cyan, magenta and yellow. Colour digital electrophotographic printing is currently in high demand. The provision of a large colour gamut depends on appropriate selection of precise colourants to produce toner capable of producing a thin layer on paper. Design/methodology/approach – Printing toners were synthesised by the emulsion aggregation method, and then evaluated for chemical constitution and effects of the colourant substituents. Findings – Results demonstrated that increasing the polarity of a pigment produced better dispersion and lower particle size with narrower distribution and even better colour reproduction. While, changing a pigment’s characteristics did not affect the toner shape or its thermal properties. Practical implications – The developed method provides a simple way to synthesise colour printing toner. Social implications – Emulsion aggregation toners provide less hazardous materials during printing. Originality/value – Evaluations of the influence of solid-state parameters and physicochemical properties of the pigments on printing toner characteristics were done for the first time.

Multidimensional Scaling of Solid-State Parameters with Plasmon Energy and In-situ Spectro-Microscopic Determination and Imaging of Material Properties

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005

Defects and Phase Change Induced by Giant Electronic Excitations With GeV Ions And 30MeV Cluster Beam

MgO and LiNbO 3 single crystals were bombarded with GeV swift heavy ions (Pb, Gd) and 30MeV C60 clusters to study the damage production induced by giant electronic processes at stopping power up to 100keV/nm. The defect creation was characterized by optical absorption, transmission electron microscopy (TEM) and Rutherford backscattering spectrometry in channeling geometry (RBS-C). In MgO point defects (F type centers) and extended defects (dislocation loops) were created by ionization processes in addition to those associated with nuclear collisions. The F-center concentration induced by electronic energy excitations was studied at different temperatures and as a function of the particle electronic energy losses. TEM revealed that dislocation loops were produced close to the particle trajectories and amorphization was never observed. On the opposite, in LiNbO3 continuous amorphous tracks were evidenced above a threshold near 5keV/nm. The dependance of this effects with various solid state parameters will be discussed.