Supramolecular pentagons

Scheme 7. Supramolecular pentagon. Reproduced from reference 5. Copyright 2000American Chemical Society.

Figure 3. Supramolecular pentagon formed with five-by-five methodology. Reproduced from reference 27. Copyright 2001 American Chemical Society.

In the case of the spherical nano-ohjects (Table 14.1), formed by 12 pentagonal (Mo)Mo5 units linked by 30 mono- or dinuclear linkers, there is, for each species, a nanoscaled capsule cavity and 20 size-tunable specific nanopores of the type M 0 (for example with n = 6 or 9), which can act as substrate specific receptors [8]. The cavity can even house smaller polyoxometalates, like different Keggin ions, to form a supramolecular nanocomposite of a unique kind (see Figure 14.10) [13]. Some typical interesting reactions are ... 

F. Patthey, and W. D. Schneider, Conservation of chirality in a hierarchical supramolecular self-assembled stmc-ture with pentagonal symmetry, Angew. Chem., Int. Ed. 44(33), 5334-5337 (2005). 

The coordination geometry around antimony is pentagonal bipyramidal, with a benzene molecule occupying one axial site another axial site is occupied by a chlorine atom bonded to antimony by a primary Sb-Cl bond. In the equatorial plane there are two primary (normal covalent) Sb-Cl bonds (in the range 2.340-2.378 A) whereas three other secondary Sb- -Q interactions (range 3.401-4.04 A) distort the geometry and contribute to the formation of the supramolecular architecture. The supramolecular assembly exists only in the solid state in solution or melt disassembly occurs. 

Figure 6.18 (a) Pentagonal and hexagonal structures of per-hydro)ylated pillar[5]-arene 6.9 and pillar[6]arene 6.25. (b) 2D supramolecular polymerization by oxidation of hydroquinone units. 

Aside from supramolecular squares and triangles, a variety of other two-dimensional species have been synthesized over the past number of years. Included amongst these are pentagons and hexagons (Schemes 7 and 8). 

Indeed, Lehn and co-workers were able to produce a supramolecular, star-like pentagon when the iron starting material was iron(II) chloride (Scheme 7 5,26). Additionally, they were able to produce a supramolecular, star-like... 

Supramolecular hexagons via either a three-by-three angle-angle approach similar to that of the two-by-two squares or a six-by-six angle-side approach similar to that of the four-by-four squares are much more common tlm the five-by-five pentagons (5,30-33). As such, a host of research into these types of systems appears in the literature, and many interesting species abonnd. 

---