Palladium complexes 1122 INDEX

Goodall [7] polymerized norbomene using the cationic chromium-palladium/ boron pair complex, (IV) to aM of roughly 1,200,000 daltons with a PDI index of 1.2. 

However, this assumption is not necessarily justified. Even for a well-faceted nanoparticle there are a number of nonequivalent adsorption sites. For example, in addition to the low-index facets, the palladium nanoparticle exhibits edges and interface sites as well as defects (steps, kinks) that are not present on a Pd(l 1 1) or Pd(lOO) surface. The overall catalytic performance will depend on the contributions of the various sites, and the activities of these sites may differ strongly from each other. Of course, one can argue that stepped/kinked high-index single-crystal surfaces (Fig. 2) would be better models (64,65), but this approach still does not mimic the complex situation on a metal nanoparticle. For example, the diffusion-coupled interplay of molecules adsorbed on different facets of a nanoparticle (66) or the size-dependent electronic structure of a metal nanoparticle cannot be represented by a single crystal with dimensions of centimeters (67). It is also shown below that some properties are merely determined by the finite size or volume of nanoparticles (68). Consequently, the properties of a metal nanoparticle are not simply a superposition of the properties of its individual surface facets. 

In summary, a Pd(l 1 1) single-crystal surface is not sufficient to model the complex adsorption behavior of palladium nanoparticles, even for nanoparticles which mostly exhibit (111) facets. High Miller index stepped or kinked single-crystal surfaces may provide better models of nanoparticles. However, one should remember that CO adsorbed on defects of defect-rich Pd(l 11) became invisible at high coverages Furthermore, it will be demonstrated in a following section that the... 

Refractive index studies allow measurements of the birefringence, but also of the polarisability. The mean polarisability (a) can be determined using an isotropic liquid solution, whereas the polarisability anisotropy (Aa) is measured in the mesophase. Polarisability studies have been made on palladium, platinum, iridium and silver metallomesogens, and show a higher polarisability for the metal complexes than for their parent ligands. ... 

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