Supramolecular aggregate/assembly

Fig. 7. Formation of a supramolecular aggregate composed of a compound containing nine melamine rings (the three-layered nonamelamine derivative A) and nine molecules of neohexylisocyanurate (B). Of the 16 possible conformers that can result, two are shown The first has the nine molecules of B arranged in three rosettes of three molecules each, stacked atop each other in the second, the rosettes are staggered with respect to each other such that the rosettes in the first and third layers of A are aligned with each other, but not with the rosette in the second layer. The supramolecular assembly is stabilized...

Size and shape Certain steric effects can be achieved using characteristically wedge-shaped dendrons. Thus, self-assembling dendrons have been connected to supramolecular aggregates with defined dimeric or hexameric structures. Such aggregates can form columnar superstructures which reveal liquid-crystalline properties. Spherical superstructures arise from the self-assembly process when conical dendrons are used14 14,161 Similar... 

Figure 1.2 Schematic illustrating the difference between a cavitate and a clathrate (a) synthesis and conversion of a cavitand into a cavitate by inclusion of a guest into the cavity of the host molecule (b) inclusion of guest molecules in cavities formed between the host molecules in the lattice resulting in conversion of a clathrand into a clathrate (c) synthesis and self-assembly of a supramolecular aggregate that does not correspond to the classical host-guest description.

We saw in Figure 1.2c that supramolecular chemistry is not just about solid state or solution host-guest chemistry but increasingly emphasises self-assembly and the construction of multi-nanometre scale devices and ultimately materials based on nanometre-scale components (a nanometre is 10 9 of a metre). Strict supramolecular self-assembly (Chapter 10) involves the spontaneous formation of a multi-component aggregate under thermodynamically controlled conditions based on information encoded within the individual building blocks (referred to as tectons ) themselves. The aggregate might comprise only one kind of molecule (as in the multiple copies of the same protein that comprise... 

These examples serve to highlight that supramolecular self-assembly and topo-chemical diacetylene polymerizations are a perfect match. Topochemical diacetylene polymerizations are an advantageous means of covalent capture for the reasons outlined above. The required order may, on the other hand, be provided by supramolecular self-assembly, which extends the scope beyond singlecrystalline monomers. This aspect becomes particularly important in the case of functional monomers in order to address specific applications. However, in contrast to previous investigations, the targeted preparation of hierarchically structured poly (diace tylene)s with a defined, finite number of strands required the presence of equally well-defined, uniform supramolecular polymers [106] with the propensity to form predictable superstructures, instead of micellar or vesicular ID aggregates. 

Entrapment of guests within self-assembled capsules provides a fourth method for the construction of chiral supramolecular aggregates. In fact, confinement of guests into cavities with a proper shape and size limits their available space and allows the control over their reciprocal positioning. This reflects directly into their mutual electronic and steric interaction and, as a consequence, in their stereorecognition (Fig. 4D). 

This chapter deals with formation of cyclic 2D and 3D structures in solution by self-assembly of two or more components using hydrogen bonds as the major interactions. Obviously, the formation of a defined supramolecular aggregate stabilized by non-covalent forces is a thermodynamically driven process which reflects a balance between enthalpy and entropy. Consequently, the product of a non-covalent macrocyclic synthesis must be evaluated and predicted in terms of thermodynamic minima in an equilibrium mixture. 

---