Interpenetrated structures diamondoid networks

Figure 4 (a) Perspective views of the structure of a single adamantane cage with TUBA connections between cadmium ions, (b) View of the structure of 4d2DMF, showing the fourfold interpenetration of diamondoid networks. (Reprinted with permission from Ref 24. Copyright (2009) American Chemical Society.)... 

Network topologies can be extremely complex exhibiting complexity such as interpenetration. They are commonly described either by analogy to known structures (diamondoid, a-Po, NbO etc) or using either Wells or Schafli symbols. 

In the crystal structure of CU2O, each O atom is surrounded tetrahedrally by four Cu atoms, and each Cu atom is connected to two O atoms in a linear fashion. Hence the node is the O atom, and the rod is O-Cu-O. Figure 20.4.2 shows a single CU2O diamondoid network, and the crystal structure is composed of two interpenetrating networks. 

Crystal structure of CU2O (a) single diamondoid network and (b) two interpenetrating networks. 

Wuest has demonstrated that the pyridone moiety also generates a hydrogen-bonded supramolecular synthon that is suitable for building extended arrays.67 Remarkably, methanetetra(6-phenylethynyl-2-pyridone) exhibits a diamondoid network, sevenfold interpenetration and cavities large enough to enclathrate butyric or valeric acid.27 Wuest introduced the concept of tectons to describe molecules that inherently possess the molecular structure and intermolecular recognition features to predictably self-assemble into crystalline networks. He followed this study with several other examples of diamondoid networks sustained by the pyridone moiety 27c d... 

Finally, it should be noted that there are supramolecular synthons that do not rely upon hydrogen bonds. In this context, N—Br interactions were exploited to propagate a diamondoid network in the cocrystal formed by carbon tetrabromide and hexamethylenetetraaamine. This structure also represents a different but equally effective form of the modular approach two tetrahedral nodes with one possessing donor functionality and the other acceptor functionality only. The structure of the cocrystal formed by carbon tetrabromide and hexamethylenetetraaamine exhibits twofold interpenetration and does not enclathrate solvent or guest. 

The tendency of 2-pyridones to form hydrogen-bonded dimers (Fig. 8c) was exploited by Wuest and co-workers in the formation of diamondoid structures based on rigid tetrapyridones such as 9 [17]. Crystallisation of 9 from butyric acid/methanol/hexane gave the anticipated diamondoid network, which is sevenfold interpenetrating [75] and contains butyric acid molecules present in the pores. 

Figure 8.75 (a) Diamondoid networks and their components. Normal ice Ih has a hexagonal arrangement but two diamondoid polymorphs are known, (b) twofold interpenetration of adamantoid cages in a diamondoid structure (reproduced by permission of The Royal Society of Chemistry). 

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