Throngh-bond interaction

FIGURE 18. The symmetty-adapted, orthogonal linear combinations of the localized u-oibitals of norbomadiene 75 belonging to the irredncible representations Ai and B2 of the point gronp C2v The A and B l combinations are the relay oibitals for throngh-bond interaction between and n j which define, according to eqnation 56, the orbitals and... 

The lone pairs on the oxygen atom in disiloxane, disilaoxirane, and 1,3 -cyclodis-iloxane have been shown [131] by the bond model analysis [132-134] to delocalize significantly to the silicon atoms throngh the interaction of the n-orbital... 

Notably, the bicyclic radical 41 is localized, in sharp contrast to the allylic-type delocalization of cyclotrigermenyl radical 39 and cyclotetrasilenyl radical 40. The obvions reason for snch a distinction is the absence of the neighboring to the Ge-radical center tt-bond necessary for the effective throngh-bond delocalization of the unpaired electron in the radical 41, whereas the through-space radical-C=C bond interaction is not sufficiently strong to indnce the effective delocalization of the unpaired electron. 

The third example in Scheme 3.64 represents the cation-radical of 1,3,6,8-tetraazatricyclo [4.4.1.F ]dodecane. Zwier et al. (2002) prodnced evidence of instantaneous electron delocalization over the four equivalent nitrogen atoms. This extensive delocalization in a completely saturated system is a principal featnre of the third example and reveals the consequences of orbital interactions throngh space and bonds. The space—bond delocalization can serve as a driving force for the cation-radical rearrangements as it has recently been exemplified by transformation of the phenyl-honsane cation-radical into a mixtnre of phenylbicyclononenes (Gerken et al. 2005). 

Figure 1 Chemical functionalization of carbon nanotubes (CNTs) involves the covalent bonding of a variety of chemical groups (R) to the graphitic lattice of CNTs. Supramolecular approaches can, in principle, enable the attachment of the same functionality (R) throngh nondestructive noncovalent interactions to CNTs in both an exohedral and endohedral fashion.

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