Metalloids in the Backbone

Polymers incorporating metals or metalloids in their backbones possess a very large variety of structural features. For example, the polymer can contain metal- or metalloid-carbon a bonds (46,47) or n bonds (48) in their backbones.  

There are munerous examples of polymers that contain metals and metalloids coordinated to noncarbon elements. In these cases, the properties of the polymers are highly dependent on the ligands that are utilized. Polymer 49 is an example of a zinc porphyrin polymer. It was found that incorporation of different substituents (electron acceptors or electron donors) on the aromatic rings in the polymer backbone altered the electronic properties of these materials. 

Braid-shaped structures have been prepared as in the product of the phenylte-trazolate anion with metal ions. The Ni(II) and Fe(II) adducts (50) give extremely viscous, aqueous solutions of polymers from which flexible sheets and threads have been made. 

Metal-containing polymers exist in a plethora of wonderful shapes and structures including rods, sheets, and coils. There are a number of interesting structural classes of polymers known as stacked systems. These include both the shish-kebab type and the polydecker sandwich-type structures. A metal phthalocyanine structure with bridging pyrazine units (51) resembles a shish-kebab, in which the metal-pyrazine chain represents the skewer.  

Stacked phthalocyanine polymers (52) with oxygen bridges between the metal atoms have been prepared by dehydration of the phthalocyanine complexes of Si, Ge, and Sn to produce face-to-face stacking polymers. When the oxygen-bridged systems are oxidatively doped, they become electrically conducting or semiconducting. 

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