We present a free web application for the calculation of the buried volume (% V Bur ) of NHC ligands. The web application provides a graphic and user-friendly interface to the SambVca program, developed for the calculation of % V Bur values not only of NHC ligands but also of other classic organometallic ligands such as, for example, phosphanes and cyclopentadienyl-based ligands. To provide a reliable pro-

Complexes of iridium bearing NHC (NHC ) N-heterocyclic carbene) ligands were synthesized and fully characterized. The series [(NHC)Ir(cod)Cl] were obtained by simple cleavage of [Ir(cod)Cl] 2 . The [(NHC)Ir(cod)Cl] complexes were reacted with excess carbon monoxide, leading to [(NHC)Ir(CO) 2 Cl]. The infrared carbonyl stretching frequencies of these were recorded to quantify the electronic parameter of NHC ligands. X-ray diffraction study results allow for determination of NHC steric parameters within this series. These data allow for comparison with other ligand families.

No abstract

The influence of thermal treatments and supercritical carbon dioxide extraction procedures on the crystal structure and morphology of sPS aerogels is investigated mainly by wide-angle X-ray diffraction and scanning electron microscopy. The use of supercritical CO2 extraction treatments allows the obtaining of high porosity aerogels with fibrillar morphology, not only exhibiting the nanoporous δ phase but also the dense γ and β crystalline phases. Moreover, a procedure to obtain high-porosity aerogels exhibiting the recently discovered nanoporous ε-form is described. Measurements of the sorption capacity of organic molecules from diluted aqueous solutions, for aerogels presenting different crystalline phases, clearly indicate that ε-form aerogels are the only ones suitable for detection and removal of long organic pollutants.

No abstract

A model for molecular hydrogen interacting with aliphatic and aromatic hydrocarbons is presented. The model has been derived using ab initio techniques and molecular dynamics simulations. In particular, quadrupole moments of hydrogen, and variation on energy with intermolecular distance of different conformations for the hydrogen-benzene couple were calculated using the Møller-Plesset method. Hydrogen was modelled using a two-centre Lennard-Jones potential plus electrostatic interactions. Lennard-Jones parameters were optimized on the basis of a correct reproduction of experimental data of hydrogen solubility in benzene and cyclohexane, calculated using the test particle insertion method. Different sets of parameters for specific interactions (hydrogen-aliphatic and hydrogen-aromatic systems) were considered avoiding the simple use of Lorentz-Berthelot combining rules. Additionally, structural and thermodynamic properties of hydrogen-benzene, hydrogen-cyclohexane and hydrogen in an equimolar mixture of benzene-cyclohexane at different low concentrations of hydrogen were investigated by means of molecular dynamics simulations. Electrostatic charges were taken from ab initio quantum mechanical calculations but after careful analysis of the calculated properties, their irrelevance was evidenced. Moreover, Coulombic interactions make simulations more expensive and, therefore, we do not recommend their inclusion in the modelling of hydrogen-aliphatic and aromatic interactions.

Two different kinds of organoclays were prepared by mixing a pristine montmorillonite and a double‐chain ammonium salt in many different thermoplastic or elastomeric polymers. Independently of the chemical nature of the considered polymers, the obtained organoclays presented a basal spacing of 4 or 6 nm, when the mixing occurred in the absence or in the presence of a small amount of stearic acid (SA), respectively. X‐ray diffraction and Fourier transform infrared measurements support the hypothesis that these two kinds of organoclays correspond to paraffin‐type tilted and perpendicular bi‐layer intercalates, respectively. The co‐intercalation of SA molecules with the double‐chain amphiphile is suggested, to explain the observed expansion of the clay interlayer distance. The obtained results suggest an easy way to control the organoclay structure in polymer composites. Moreover, the authors on the basis of these results propose a criticism to the extensive literature that systematically explains most d basal spacing increase observed for clays in polymer with the penetration of apolar polymer chains in the clay interlayer space. Copyright © 2010 John Wiley & Sons, Ltd.

Summary: In this manuscript the influence of supercritical carbon dioxide extraction temperature on the morphology, the porosity, and the crystalline structure of syndiotactic polystyrene aerogels is investigated. Results show that depending on the extraction temperature, δ‐form, γ‐form, and β‐form high porosity aerogels characterized by a fibrillar morphology can be obtained.