Search

The temperature variation of the thermal conductivity, the electrical resistivity and the thermoelectric power of a graphitized polyimide film has been measured in the temperature range 2 < T < 300 K. The effect of electrochemical intercalation with FeCl4- ions has also been studied. The thermal conductivity results confirm the high degree of graphitization that may be obtained with polyimide films. It shows how intercalation increases the structural disorder and how the intercalate substantially contributes to the thermal conductivity at low temperatures. The electrical-resistivity and thermoelectric-power measurements reveal that the density of free carriers is about three times lower in stage-2 FeCl4- solvated intercalation compounds obtained by an electrochemical way than in stage-2 FeCl3 compounds synthetized by a classical method.

Li-graphite compounds were recently obtained under pressure with a Li/C ratio as high as 1/2. At ambient temperature and pressure, the system relaxes to a composition close to Li7C24, and the IR frequencies, the positions of the X-ray diffraction lines and Li NMR point to a lattice composed of two-dimensional clusters of 7 Li atoms on a substrate of 24 C atoms, but neither the calculated structure factor nor 7Li NMR give evidence of local axial symmetry, as found for instance in LiC6.The Madelung energy of structures obtained by modifying the positions of the Li atoms in the clusters was calculated. A significant gain in stabilization was found for a radial shift of the peripheral Li atoms placing them about 3.2 Å from each other within each cluster, in a configuration reminiscent of a Penrose lattice, with 5 or 6 nearest neighbors for each Li. A rough modelization of Li-Li covalency was also included by localizing some negative charge between first-neighbor Li+ ions, with a consequent further gain in stability. The Madelung energy is comparable to that of other LiCn structures (2 ≤ n ≤ 6). In all cases, energetically favorable structures are characterized by 'smooth' local potentials of electrostatically equivalent species.

Partially graphitized carbons were functionalized by carboxylic groups which were esterified with 4‐hydroxybenzaldehyde. A chiral diphosphine moiety, analogous to the DIOP framework, was then synthesized from the aldehyde function. The supported chiral diphosphine was transformed into a rhodium catalyst. Preliminary results of asymmetric hydrogenation or asymmetric hydrosilylation are described.

The layered Ni(CnH2n+1NH2)2Ni(CN)4acts as a host structure for amines, yielding Ni-(CnH2n+1NH2)2Ni(CN)4,xCnH2n+1NH2(with 0 ≤ x ≤ 0.4 and 12 ≤ n ≤ 16) which are easily prepared by various procedures including solid–solid reaction. The guest can be removed and re-included; it can be replaced by aromatics. Phase transitions of the clathrate (with amines as guest) occur in the range 55–85 °C, obviously related to the transitions previously observed in the parent compound Ni(CnH2n+1NH2)2Ni(CN)4.