Chromophoric interactions in [60]fullerene–porphyrin dyads investigated by solid-state UV–Vis and IR spectroscopies

Solid-state electronic (UV–Vis) and vibrational (IR) spectra of several fullerene–porphyrin conjugates were recorded in KBr in the spectral range between 400 and 50,000 cm⁻¹. It was observed that significant redistribution of the charges occurs in both fullerene and porphyrin moieties upon covalent linkage. This effect is mainly observed as shifts of both electronic and vibrational bands in comparison with the respective free porphyrin and fullerene features. Variable temperature IR measurements were also performed.     

Electrochemistry of the two-dimensional heteronuclear [Fe3Pt3(CO)15] n clusters (n=2-, 1-, 0): MO treatment of the skeletal adjustments in 86-84e − congeners

Electrochemical studies show that it is possible to move step-wise and reversibly between the redox congeners of the series [Fe₃Pt₃(CO)₁₅] ⁿ ,n=2-/1-/0. By contrast, a multielectron reduction of the dianion leads to an irreversible demolition of the species. When [Fe₃Pt₃(CO)₁₅]^2– is treated with one or two equimolar amounts of the oxidant [Fe(C₅H₅)₂]⁺, the oxidized species (n=1- andn=0) can be also obtained. It can be established or extrapolated from the already known structures of the dianion and the monoanion that the successive oxidations strengthen the inner Pt-Pt linkages of the overall quasiplanar Fe₃Pt₃ skeleton. MO analysis, by establishing the antibonding nature of the frontier level from which the electrons are added or subtracted, allows the correlation of the bonding features of the inner Pt₃ skeleton with the redox propensities of the system.     

On the existence of collisionless equivariant minimizers for the classical <Emphasis Type="Italic">n</Emphasis>-body problem

We show that the minimization of the Lagrangian action functional on suitable classes of symmetric loops yields collisionless periodic orbits of the n-body problem, provided that some simple conditions on the symmetry group are satisfied. More precisely, we give a fairly general condition on symmetry groups G of the loop space for the n-body problem (with potential of homogeneous degree -, with >0) which ensures that the restriction of the Lagrangian action to the space ^G of G-equivariant loops is coercive and its minimizers are collisionless, without any strong force assumption. In proving that local minima of ^G are free of collisions we develop an averaging technique based on Marchals idea of replacing some of the point masses with suitable shapes (see [10]). As an application, several new orbits can be found with some appropriate choice of G. Furthermore, the result can be used to give a simplified and unitary proof of the existence of many already known minimizing periodic orbits. Mathematics Subject Classification (2000) 70F10, 70F16, 37C80, 70G75     

High-precision measurements of light-induced torque on absorbing microspheres

Laser beams have been demonstrated to be capable of exerting torque as well as forces on microparticles. Using a custom magneto-optic manipulator, we directly measured the torque exerted by laser light on absorbing microspheres as a result of the transfer of spin angular momentum. A general method for measuring torque has been developed, and the experimental apparatus has shown a sensitivity of approximately 1 pN/nm.     

Radiochemical characterisation,heavy metal determination and morphologic evolution of coastal sediments in the Ravenna area (Italy)

The basic aim of this work was to achieve a preliminary but integrated characterisation of an area of the Ravenna littoral coastline. The use of suitable computerised procedures has allowed the reconstruction of the morphological evolution of this area by means of historical and recent cartography. Coastal sediments were characterised by sampling 3 cores at about 2 km offshore. The following aspects were studied: 1) Mineralogical characterisation of both the total and the fine fraction of sediments by X-ray Diffraction. 2) Characteristion of sedimentary horizons by radiodating. 3)Magnetic susceptibility profiling. 4) Determination of some heavy metals (Cu, Pb, Zn, Cd) by anodic stripping voltammetry.     

A counterintuitive, yet efficient synthesis of bis(indenyl)zirconium dihalides

The use of bisindenyl zirconium dimethyl in the synthesis of the corresponding dihalides is described. The synthesis of Ind₂ZrCl₂ has been carried out, cleanly and quantitatively, by chlorination of Ind₂ZrMe₂ (2) with a variety of inorganic chlorides, including BCl₃, SCl₂ in either toluene or methylene chloride, and HCl in Et₂O. The latter method is the preferred one, since it produces methane as the only byproduct, and the formed Ind₂ZrCl₂ precipitates quantitatively from the Et₂O solvent: a simple filtration then gives the analytically pure product in quantitative yield. Ind₂ZrBr₂ and Ind₂ZrI₂ are obtained by reacting 2 with Br₂ and I₂, respectively. The ‘inverse’ synthesis of metallocene dichlorides by chlorination of their dimethyl ‘derivatives’ has advantages compared to the classic method: first, Ind₂ZrCl₂ is obtained in higher yield (90-96%); second, it is easier to purify (at the dimethyl stage) and is obtained free from LiCl. Five bisindenyl zirconium complexes with different sigma ligands have been investigated in solution propylene polymerizations: it is found that the σ-ligands have no relevant influence on the catalyst activity, nor on the polymer properties.     

Low-temperature synthesis of soluble and processable organic-capped anatase TiO2 nanorods

We demonstrate the controlled growth of high aspect ratio anatase TiO2 nanorods by hydrolysis of titanium tetraisopropoxide (TTIP) in oleic acid (OLEA) as surfactant at a temperature as low as 80 degrees C. Chemical modification of TTIP by OLEA is proven to be a rational strategy to tune the reactivity of the precursor toward water. The most influential factors in shape control of the nanoparticles are investigated by simply manipulating their growth kinetics. The presence of tertiary amines or quaternary ammonium hydroxides as catalysts is essential to promote fast crystallization under mild conditions. The novelty of the present approach relies on the large-scale production of organic-capped TiO2 nanocrystals to which standard processing of colloidal nanocrystals, such as surface ligand exchange, can be applied for the first time. Concentrated colloidal titania dispersions can be prepared for a number of fundamental studies in homogeneous solutions and represent a new source of easily processable oxide material for many technological applications.     

Secondary ion mass spectrometry and X-ray photoelectron spectroscopy investigation on chemical vapor deposited CeO(2-)ZrO(2)-TiO(2) thin films

Mixed CeO(2)-ZrO(2) systems have attracted widespread interest for their use in three-way catalyst (TWC) technology for automotive exhaust conversion to non-toxic products. In this work, CeO(2)-ZrO(2) thin films were deposited, via chemical vapor deposition, in order to obtain nanoscale materials with a high surface-to-volume ratio, with precise control of system properties. The addition of TiO(2) as buffer layer was also investigated. Cordierite was chosen as substrate, being the usual refractory material for catalytic mufflers. The multilayers were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). In particular, the combination of SIMS and XPS allowed us to investigate both surface and in-depth chemical composition, studying also film-intermixing phenomena induced by annealing processes.