Coordination polymers three-dimensional networks

The highly crosslinked, three-dimensional network structure of the Cr(III) coordination polymer is considerably more stable at elevated temperatures than the Zn(II) polymer or the other transition metal polymers which have been studied. For example, while the Cr(III) sample sustains a loss in weight of about 30% at 850°C., the Zn(II) coordination polymer loses 60% under similar conditions. 

As polymer matrices, various polyethers are frequently used because the mobile metal ions existing within are not only solvated but also coordinated by oxygen atoms originating from polyethers, e.g., poly(ethylene oxide)/PEO. The respective materials are often cross-linked, and they are bound together to form single three-dimensional networks. 

Figure 7-6. Infinite three-dimensional network of the coordination polymer 38 prepared from Cdp2 and 37 (Cd as large circles, imidazole bridges as lines).

An example of a three-dimensional penetrating network is the solvated [(ZnCl2)3(35)2] 56 [139], The triazine molecules are part of threefold connecting knots (Fig. 7-17). The zinc atoms have a nearly tetrahedral coordination geometry with two N atoms of 35 and two chlorine ligands. A distorted network is obtained. The self-assembly of CUSO4 in water and l,3-bis(4-pyridyl)propane in ethanol results in 57 which presents a three-dimensional architecture sustained by two different types of coordination polymer one-dimensional ribbons of rings and two-dimensional layers (Fig. 7-18) [138]. 

Li H, Wang H, Wang H, Li B. A novel (2,3,5)-connected double interpenetrating three-dimensional network cadmium coordination polymer with flexible tri(triazole) and dicyanamide ligands. Inorg Chem Commun 2011 14(1) 49-51. 

Most of the remaining examples of supramolecular alkali metal compounds involving r-coordination are alkoxides, siloxides, and thiolates. In polymeric sodium phenolate ( NaOC6H4Me-4 2]n, 79 [78], the / -arene interaction of the phenolate ligands with sodium plays a crucial role, because it restricts the structure of the resulting polymer to a one-dimensional stack of [NaOC6H4Me-4]2 dimers and prevents the formation of a fully extended three-dimensional network. 

Catalysis - Porous three-dimensional networks can be viewed as zeolite mimics and can exhibits similar properties in some cases. The enclosed environment within charmels, akin to zeolites (Section 4.2) and discrete capsules (see Chapter 3, Section 3.5), can provide novel reactivity or catalytic ability and can be size- and shape-selective. Coordination polymers offer an advantage over traditional zeolites in that chiral channels are able to be constructed by using chiral ligands. 

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