Interpenetration 3D nets

Interpenetrating 3D Nets Each Containing Two Types of Nodes with Different Connectivities... 

We classify the modes of interpenetration of 3D nets in terms of the topologies of the individual nets. 

Figure 32. (a) A simple 6-connected 3D net (4V) formed by linking nodes with trigonal prismatic geometry. A single net in [Eu Ag(CN)2 3(H20)3] has this topology, (b) Three nets of the type shown in (a) that interpenetrate in [Eu Ag(CN)2 3(H20>3]. Circles represent Eu. Linear connections represent EuNCAgCNEu links (shown in full in the central net). 

Fig. 10 (a) Coordination environment of Co, showing the building unit of [Co3(bpdc)3(bpy)] (8). (b) Packing diagram of one of the two nets of 8 viewed down the b axis, (c) Twofold interpenetrating 3D networks viewed down the a axis, (d) Space-filled model of 8 viewed perpendicular to the (001) plane... 

Fig. 3 Interpenetration of 3D nets (a) two interpenetrating diainondoid networks and (b) two interpenetrating a-Po nets in the structure of a-M(dca)2(pyz). (View this art in color at WWW. dekker. com.)...

Interpenetration of erystalline COFs have already been proved and reported by Yaghi et A crystalline imine-linked 3D COF-300 was prepared by condensation of 4,4, 4",4" -methanetetrayltetraaniline and ter-ephthalaldehyde (Figure 2.2). Powder X-ray diffraction analysis revealed COF-300 shared a five fold interpenetrated diamond net. Though many COFs have been synthesized to date, few interpenetration structures have been repotted because this analysis requires high erystallinity of the porous polymer. 

A final consideration is the density of the net, and the possibilities of interpenetration (see Interpenetration, Supramolecular Materials Chemistry), that is, two or more interwoven nets in the same structure. Both the srs and the ths nets have good geometrical properties for interpenetration as an identical net fits exactly into the voids of the first (these are called self-dual nets for a more stringent definition see ref. 22), whereas this is not true for the other 3D nets in Figure 6 The srs net is also less dense than the ths net, and this may also be a factor to consider. 

For 3D nets, the paralleFinclined interpenetration notation discussed above obviously does not apply, but there is nonetheless a rich variety of possible interpenedation topologies they can exhibit. 

The use of networks to describe and design crystal structures inevitably leads to the possibility of interpenetration of multiple networks. In such cases it is essential that the topology of interpenetration, as well as the individual network topology, is analysed and understood in detail. For ID and 2D networks, interpenetration can occur either in a parallel or inclined fashion, leading to overall entanglements of the same or higher dimensionality. Such systems can be described in terms of a mD(/nD) pD parallel/inclined interpenetration notation. Even highly symmetrical 3D nets such as diamond or a-Po can show, on rare occasions, different modes of interpenetration. 

Figure 3,9 Portion of the charge assisted hydrogen bonded 3D net formed by A-[Cr(2,2 -biimida20le)2(2,2 -biitnidazolato)](S04)-H20 [30] An isomorphous structure is found for [ Fe(2,2 -biimidazole>j COj-McOU [31], In these structures the net is triply interpenetrated.

Trigonal coordination around the metal ion can also lead to srs nets, such as in [Ag2(bis(phenylthio)methane)3](C104)2, shown in Figure 5.4 [16]. Two things are noteworthy about this latter structure it is formed by a single net, thus has no interpenetration, and it is formed by achiral molecular building blocks. We will return to the srs net in the interpenetration chapter as well as when we discuss 3D nets as specific synthetic targets in Chapter 12. 

The choice of the right solvent can be the difference between a 3D system and a product of lower dimensionality, both for hydrogen bonded systems and coordination polymers [17-21]. Also for the properties it may be critical, many of the 3D nets with permanent porosity have been synthesized in diethyl formamide, Dimethylformamide (DMF) or DMF/water mixtures. It has also been observed that lower concentrations of the reagents may hinder the formation of interpenetrated nets. It is believed that some solvents may form larger clusters inside uncompleted voids of a porous net and thereby help to build up the net. 

Feng R, Jiang F-L, Chen L et al (2009) A luminescent homochiral 3d Cd(ll) framework with a threefold interpenetrating uniform net 86. Chem Commun 43 5296... 

Interpenetration is less common for ID nets than it is for 2D or 3D nets, partly due to the fact that many 1D network topologies do not contain rings that can catenate and lead to interpenetration. Conversely, all 2D and 3D nets contain rings and thus interpenetration is more common. 

Figure 18 Interpenetration of nets of different dimensions (a) 1D/2D inclined interpenetration (b) 1D/3D interpenetration (c) 2D/3D interpenetration ...

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