Seven-connected nets

The RCSR currently contains some 75 uninodal seven-connected nets, but only two contain four-membered rings, svn and wfq, the remaining having three-membered rings as shortest circuits. In general, we get closer and closer to close packing as we draw more and more lines, so that the links between the nodes need to be long if we should consider the structure as 3D-net. 

Chemical considerations also move us away from the transition metals, at least if we consider building coordination networks where the nodes are single metal ions, since they are too small to accommodate sufficient number of ligands. However, there is clearly a possibility to have cluster compounds as nodes with higher connectivity, although at present we know of no such examples. 

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In Chapter 5 we saw the important class of compounds based on the six-connected pcu (primitive cubic packing, or a-Polonium) net, and we also encountered the five-connected bnn or boron nitride net. In this chapter we will explore higher connectivities further, starting with the five-connected and six connected nets and then going on to the mixed 3 5, 3 6,4 5 4 6 and 5 6 nets. We will also briefly look at some seven and eight connected nets. 

Figure 9.15 The wfq net is found in the eight coordinated compound [La(2,2 -bipyridine-A, lV -dioxide)4](BPh4)(C104)2 2.75MeOH [18]. Note that one pair of A -oxide bipy ligands binds to the same lanthanum ions making the nodes seven-connecting.

Interestingly, our example of the bcu net is taken from the same publications as the seven-connected wfq net, and it contains the same ligands but other counter ions, the formula being [La(2,2 -bipyridine-A, A -dioxide)4](CF3S03)3-4.2MeOH, [18] see Figure 9.17. 

We will consider one more net of this class since it is important to see how trigonal prismatic nodes can connect to trigonal nodes (the RCSR lists another seven three- and six-connected nets). 

Pseudo-Code Implementation The Back-propagation algorithm outlined above may be implemented by following seven steps, to be applied for each pattern p . Assume we have a neural net with L layers (/ 1,2,...,L). Let h represent the output of the neuron in the / layer hf is therefore equal to the input, <7 . The weight of the connection between li- and h[ will be labeled by Wij. 

Corrugated 6 -net fragments groups connected at 210 pm trigonal prism, Tj Pianar nets of five-, six-and seven-membered rings of B atoms trigonal prism... 

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