Chalcogen polymers

Polyatomic Chalcogen Polymers and Polymeric Tellurium Cations... 

Polymer and chain formation is another property of chalcogen-nitrogen compounds that distinguishes them from their oxygen analogues. In addition to the unique, superconducting poly(sulfur nitride) (SN) (1.24) (Section 14.2), a variety of poly(thiazyl) chains such as RS5N4R (1.25) (Section 14.3) have been characterized. Interest in these chains stems from their possible use as models for the behaviour of (SN) and as components in molecular materials, e.g., as molecular wires. 

Electrochemical methods may also be used in the synthesis of chalcogen-nitrogen compounds. For example, the electrochemical reduction of salts of the [SsNs]" cation (Section 5.3.9) in SO2 or CH2CI2 at low temperatures produces microcrystals of the superconducting polymer (SN). ... 

Polymer formation Scheme 1 Trends in neutral and cationic chalcogen chemistry. 

Thiophene and its derivatives, however, have become the most-studied chalcogen-containing monomers. Doped (oxidised) PT is highly conducting, and 3-alkyl-substituted PTs are soluble, easily characterised polymers,83 85 see Figure 7. Self-assembly is an important consideration in these substituted PTs, allowing control of the degree of planarity, n-orbital overlap, and hence optical... 

Although platinum is the metal of choice for PEM fuel cell cathodes, Paul Matter, Elizabeth Biddinger, and Umit Ozkan (Ohio State University) show that nonprecious metals will have to be developed for this type of fuel cell to become practical and widely used. Although few materials have the electrochemical properties needed to replace platinum, this review discusses candidates such as macrocycle compounds, non-marcrocyclic pyrolyzed carbons, conducting polymers, chalcogen-ides, and heteropolyacids. 

Binary Anions and Cations. The heavy pnictogens in combination with chalcogens form a large variety of anions.Although many of these binary species form oligomers or polymers with layered or framework structures, there are a number of examples of discrete anions with cyclic structures that are formed with large counterions such as tetralkylammonium or tetraarylphosphonium... 

All three heavy chalcogens form polymers with an infinite helical chain structure however, the conditions under which they are produced differ... 

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