Graphite-like overlap

Figure 2.1. Schematic representation of the HOMO of the perylene molecule (a) and graphite-like overlap mode typical of the highly conducting perylene based conductors (b)...

The alternation of double and single bonds means that each C atom has an unhybridized /7-orbital that can overlap with the /7-orbital on either side. This arrangement allows electrons to be delocalized along the entire chain like a onedimensional version of graphite. 

Scanning tunneling microscopy leads to the supposition that the primary particles consist of superimposed, scale-like layers of graphite. For this reason, the L-values determined by X-ray diffraction have to be regarded as a median overlap surface of graphite layers and not as the average size of individual crystallites. 

One of the more interesting structural findings is that the TCT intercalate is oriented perpendicular to the graphite planes. This is most likely due to the preference of the chlorine atom to interact with the graphite layers at an angle of 180 from its bond to the TT molecule. Otherwise, the overlap of the chlorine would be at the unlikely angle of 90 . 

Why is C50 so stable As with benzene and graphite, each carbon atom in C50 is attached to three other atoms and therefore is sp -hybridized. The fourth valence electron of each carbon lies in a orbital that is perpendicular to the spherical surface. These orbitals overlap to form a pi cloud outside and inside the sphere, like the pi cloud above and below the plane of a benzene ring. Hence the structure is in a sense aromatic and exceptionally stable. Indeed, Cgo was recently detected in certain black, lustrous rocks where it may have been trapped more than half a billion years ago ... 

Diamond is a covalent-network solid that has C—C rr bonds but no tt bonds. Graphite and buckminsterfuUerene have tt bonds tiiat result from the sideways overlap of p orbitals. Elemental silicon exists only as a diamond-like covalent-network solid with (T bonds sUicon exhibits no form tiiat is analogous to either graphite or buckminsterfuUerene, apparently because Si—Si tr bonds are weak. 

Anderson and Kang used ab initio methods to calculate the characteristics of proton reduction on a diamond-like cluster [6]. With recent advances in calculation methods, it has been possible to increase the sizes of clusters used in calculations, so that they become increasingly realistic. Recently, Ohwaki et al. have treated this topic using density functional theory (DFT), comparing the diamond and graphite surfaces and have found definite differences in the potential dependences of the overlap in... 

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