Covalently functionalized carbon nanoparticles with a chiral Mn-Salen: a new nanocatalyst for enantioselective epoxidation of alkenes.

A new protocol to obtain carbon nanoparticles (CNPs) covalently functionalized with a chiral Mn-Salen catalyst is described here. The new nanocatalyst (CNPs-Mn-Salen) was tested in the enantioselective epoxidation of some representative alkenes (CN-chromene, 1,2-dihydronaphthalene and cis-ß-ethyl styrene), obtaining better enantiomeric excess values than that of the catalyst single molecule, highlighting the role of the nanostructure in the enantioselectivity.

The memory-driven order-disorder transition of a 3D-supramolecular architecture based on calix[5]arene and porphyrin derivatives.

A 3D supramolecular polymer based on calix[5]arene tethered poly(p-phenyleneethynylene) with a complementary porphyrin endowed with alkanediyldiammonium functions is prepared in solution but collapses when transferred to a chemically inert solid matrix forming a dispersion of de-phasing porphyrin aggregates. We found that a short thermal shock induces the de-aggregation of the porphyrin aggregates, and a partial restoration of the original 3D-supramolecular architecture.

Selective oxidation reactions of natural compounds with hydrogen peroxide mediated by methyltrioxorhenium.

We have investigated the oxidative behaviour of natural compounds such as methyl abietate (1), farnesyl acetate (2), α-ionone (3), ß-ionone (4), methyl linolelaidate (5), methyl linolenate (6) and bergamottin (7) with the oxidant system methyltrioxo-rhenium/ H2O2/pyridine. The reactions, performed in CH2Cl2/H2O at 25 °C, have shown good regio- and stereoselectivity. The oxidation products were isolated by HPLC or silica gel chromatography and characterized by MS(EI), 1H-, 13C-NMR, APT, gCOSY, HSQC, TOCSY and NOESY measurements. The selectivity seems to be controlled by the nucleophilicity of double bonds and by stereoelectronic and steric effects.

A ratiometric naphthalimide sensor for live cell imaging of copper(I).

A new naphthalimide derivative bearing a tetrathia-azacrown for high affinity and selective binding to Cu(+) was synthesised. Copper recognition properties in solution were evaluated using (1)H NMR and fluorescence spectroscopy. Live cell imaging by confocal microscopy highlighted the capabilities of the new sensor for the two-wavelength detection of intracellular monovalent copper in neuronal cells.

An integrated X-ray and molecular dynamics study of uranyl-salen structures and properties.

Uranium complexes of bis(p-tert-butyl-salicylidene)-1,2-diphenylethylenediamine (1) and bis(salicylidene)-1,2-diphenylethylenediamine (2) have been synthesized and investigated by X-ray single crystal diffraction and MD calculations in Periodic Boundary Conditions. Both compounds form crystals which are densely packed and do not provide voids accessible to solvent molecules. The configurations adopted by 1 and 2 are determined by well defined T-shaped and π-stacking non covalent interactions between phenyl groups of adjacent molecules as well as by a network of hydrogen bonds. These interactions and the relative arrangements of the molecules, explain the packing in the crystal structures. Each uranyl moiety shows a penta-coordination in the equatorial plane perpendicular to the trans oxygens giving rise, in both compounds, to a bypiramidal geometry. As usual for this class of compounds, the 5th position is characterized by the presence of the coordinated solvent. The in silico simulations confirm this hypothesis in very fine details. Moreover, in 1, even the partial occupancy of the solvent molecule determined from the crystal structure refinement, was shown to be due to a constrained freedom of motion of the solvent molecule that can be reproduced by molecular dynamics. This suggests that the reported disorder is not due to a poor quality of the harvested crystals but to a structural feature. In further agreement with the above mentioned results, DFT calculations demonstrated that the molecular orbital configuration and energies suit the described properties of complexes 1 and 2 suggesting a potential enantioselective activity as already shown by molecules belonging to this class of compounds.

Synthesis and characterization of some chiral metal-salen complexes bearing a ferrocenophane substituent.

The C(2)-symmetrical "salen" ligand (+)-9 bearing two [5]ferrocenophane substituents has been prepared in five steps starting from readily available diacetylferrocene, p-hydroxybenzaldehyde and (R,R)-N,N'-diphenylethylenediamine. Reaction of (+)-9 with Mn(OAc)(3), Co(OAc)(2) ZnEt(2) or UO(2)(OAc)(2) gave the corresponding metal-complexes which were characterised by spectroscopic methods.