Borromean interpenetration

Figure 9.38 (a) A 6,3-sheet of [Ag2(9.14b)3] (BF4)2 and (b) the 2D— 2D parallel Borromean interpenetrating network that it forms with the means planes of the 2D sheets coincidental. The Ag atoms (spheres) lie above each other, held by argentophilic interactions, (c) Borromean rings in black on white marble at the Cappella Rucellai in the Church of San Pancrazio, now the Marino Marini Museum, in Florence. The rings form part of the coat of arms of the Borromeo family and are also said to be a symbol of the Florentine de Medici family (photograph courtesy of Prof. L. J. Barbour).37... 

Figure 4.37 (a) A (6,3)-sheet and (b) the 2D 2D parallel Borromean interpenetrating network that it forms (c) with the mean planes of the two-dimensional sheets coincidental. The Ag atoms (spheres) lie above each other, held by argentophilic interactions. 

Figure 8 (a) Borromean rings and (b) Borromean interpenetration of 2D sheets. 

Figure 8 Borromean interpenetration of (a) rings (b) 2D->2D parallel interpenetrating sheets (c) 2D 3D parallel interpenetrating...

As expected, molecule 42 assembled into 2D undulated hcb nets with large cavities through synthons 1 and 3 respectively, without or in the presence of methanol solvent (Fig. 3.23a). Three such nets are further interpenetrated through multiple C-H---71 interactions in a Borromean way that none of them are catenated but altogether they are not separable (Fig. 3.23b). One particular feature of the structure obtained from methanol is that it contains both the two different Borromean weaves shown in Fig. 3.23b with a 2 1 ratio within the same structure. 

Motivated by the above results, we tried to enlarge the cavity for more complicated interpenetration with the reliable carboxylic acid- -pyridine interaction 4. When 44 (phenazine) and 45 (bipy) are used, the corresponding linkers are only inserted to two para-edges of the hcb nets (Fig. 3.24a). Similar Borromean weaves were also formed (Fig. 3.24b). However, due to the unequal edge lengths, half of the 42 molecules in two of the three nets do not form sixfold phenyl embrace interactions (11) inside this Borromean weave. Instead, they interact with other remaining molecules from either up or down weaves. In this way, all the Borromean weaves are locked together to form a 3D polycatenated n-Borromean structure (Fig. 3.24c). 

Fig. 3.25 a Top and side view of the hexagonal nets, b One Borromean weave, c Topological view of the sevenfold interpenetrated 2D —> 3D Borromean-linked structure, one Borromean weave is in thick stick and other six in thin stick [83]... 

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