Aromatic compounds supramolecular interaction

Another type of supramolecular interaction of DNA is the intercalation of fused aromatic compounds into the stacked base pairs in double-stranded DNA (see Figure 6). Intercalation induces not only dehydration from the polar groups in intercalator but also concomitant unwinding, lengthening, dehydration, and stiffening of the DNA double helix. 

Noncovalent interactions with belt- or tube-like host molecules might also be suitable to a separation of carbon nanotubes by diameter. Cyclodextrines or beltshaped aromatic compounds could be named as examples here. They may not have proven their applicability as selective complexing agent yet, but considering their geometry reveals favorable dispositions for a discriminative interaction with certain nanotubes. Supramolecular arrangements with carbon nanotubes are also discussed in Section 3.5.7. 

A great variety of possibilities are available when a metal is part of a linear or crosslinked macromolecule (Section 1.2.1, Fig. 7-1). One possibility is the covalent incorporation of a metal into a homochain (metal-metal connections) or a heterochain (metal-heteroatom connections). Coordinative bonds between a metal ion and another coordinating donor group can lead to linear chains or to supramolecular organizations when coordination polymers are formed. n-Bonds between rt-rich aromatic compounds and metal ions can result in polymeric metallocenes. Covalent and coordinative bonds are realized in cofacially stacked metal complexes. In addition, dendrimers containing the interaction of metals and another group in different bonds are treated in this chapter. 

Planar coordination compounds with aromatic ligands, especially those having extended 7r-systems, show 7r-7r interactions in the solid state. The ligands shown in Figure 8 form complexes with silver(I) which have a supramolecular structure through 7r-7r interactions.586-596... 

The dominant supramolecular synthon present in these compounds is the pi-halogen dimer (PHD) interaction [22], This efficient packing motif results from two inversion-related host molecules packing such that one bromine atom from each is situated in the cleft of its V-shaped partner (Figure 3), in addition to aromatic endo, endo-facial interaction. 

The widespread occurrence of these ligands is not fortuitous, but reflects the folklore of laboratories undertaking synthesis, where it is appreciated that compounds with phenyl substituents and aromatic peripheries often have lesser solubilities in synthetic reaction mixtures, and therefore crystallize. It is also common but undocumented knowledge that compounds with phenyl substituents frequently form high-quality crystals. The prevalence of phenylated ligands and aromatic peripheries and the influences of specific phenyl-phenyl interactions in supramolecular chemistry are dubbed the phenyl factor. 

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