Supramolecular framework

This is not to say, however, that supramolecular assemblies can only affect reactivity kinetically (i.e., by bringing reagents into proximity or providing a spatial barrier between them, as in the P4 example earlier). An important example of the perturbation of a thermodynamic equilibrium by a supramolecular coordination cage is the increased acidity of encapsulated amines within the M4L6 assembly shown in Fig. 17 [29], A wide variety of amines can be encapsulated within the supramolecular framework, bound as the protonated ammonium species. 

Access to non-symmetrically substituted, highly functionalized poly(bipyridines) would have great utility in the construction of supramolecular frameworks involved in photochemical, electrochemical, or catalytic systems. The Stille reaction provided a departure from the classical methods for the assembly of these skeletons. To this end, the symmetrical bromopyridine 263 participated in cross-coupling with stannane 264 producing bipyridine 265. The remaining functionality was then exploited to further elaborate these systems [95]. 

Silver cations form only rather labile -complexes with aromatic hydrocarbons. The nature of the complex formation may be described as solvation of silver salts in arene solution. Supramolecular framework structures can be isolated upon concentration, and the structure of many of these solvates has been determined2. The Ag(I) cations are found to be mostly r 2 or ry bound to the arene, but the coordination is weak and arene may be removed already at ambient temperature in a vacuum. This class of compounds for which no synthetic strategy is required, is no longer considered in this chapter which is orientated towards preparative methods. The adducts have not yet found any significant applications. 

We define polymorphic supramolecular isomers as supramolecular frameworks built from the same molecular components using the same interactions, i.e., supramolecular synthons (M-L, H-bonding, etc.), in all isomers giving rise to the same localized geometries but different framework topologies. To illustrate this terminology, we outline three examples of this class of isomerism. 

We define structural supramolecular isomers as supramolecular frameworks built from the same molecular components using different supramolecular interactions. Examples of structural supramolecular isomerism in coordination polymers are relatively rare, which probably reflects the requirement of multiple interactive modes being present in a single building-block, ligand, or hydrogen-bonding moiety. 

We define pseudopolymorphic supramolecular isomers as supramolecular frameworks built from the same molecular components but with different noninteracting guest molecules giving rise to different framework topologies. 

As the above description, neat imidazolium ILs have supramolecular framework. Furthermore, up to now, much evidence indicated that some of the supramolecular networks can be reserved when ILs are mixed with other materials and inclusion-type structures are formed. 

In addition, no direct hydrogen bonds between cations and anions were observed in the crystal structure of [l,3-dibenzylimidazolium]Br HiO, but water molecules connected anions and cations in the supramolecular framework (Leclercq et al., 2009c). In other words, water molecules were included in the crystal lattice. 

Thus, the existing states of water molecules in the liquid and crystal phases support the hypothesis of polar and non-polar regions of the supramolecular network. From another point of view, at low water content, the water could be regarded as guest included in the supramolecular framework of imidazolium ILs. 

In addition, when ILs are used as solvents, how will the supramolecular structures of ILs themselves affect the formation of supramolecular assemblies. For example, when the surfactant is added into the IL/oil mixture, two cases would happen. If the hydrophobic interactions between oil and surfactant are stronger than the interactions between IL and oils, liquid clathrate can be destroyed and O/IL microemulsions form. Otherwise, a new state would exist instead of O/IL microemulsions. However, in the reference, this field has not been mentioned. Moreover, because trivial water is difficult to be removed and could be included in the supramolecular framework of imidazolium ILs, ILs are not pure, which makes the system more complicated. This supramolecular structure may also affect the formation of supramolecular assemblies. Recently, we noticed that water plays the key role in the formation of IL based microemulsions. A small quantity of water can lead to great change in the phase diagram of IL/TX-100/ oil ternary systems. Therefore, the effect of the supramolecular structures of ILs on the formation of supa-amolecular assemblies is another valuable subject. 

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