Backbone structure metal coordination polymers

The sensor covalently joined a bithiophene unit with a crown ether macrocycle as the monomeric unit for polymerization (Scheme 1). The spatial distribution of oxygen coordination sites around a metal ion causes planarization of the backbone in the bithiophene, eliciting a red-shift upon metal coordination. They expanded upon this bithiophene structure by replacing the crown ether macrocycle with a calixarene-based ion receptor, and worked with both a monomeric model and a polymeric version to compare ion-binding specificity and behavior [13]. The monomer exhibited less specificity for Na+ than the polymer. However, with the gradual addition of Na+, the monomer underwent a steady blue shift in fluorescence emission whereas the polymer appeared to reach a critical concentration where the spectra rapidly transitioned to a shorter wavelength. Scheme 2 illustrates the proposed explanation for blue shift with increasing ion concentration. 

Vast arrays of metal-containing polymers have been produced that offer a wide variety of properties. Key milestones in the history of this diverse topic and a sense of its growth and importance were discussed in this chapter. While initial efforts focused on polysiloxanes, today s efforts are quite diverse and include the production of multisite catalysts, variable oxidation state materials, and smart materials where the precise structure can be changed through the introduction of different counterions. These polymers have been produced by all of the well-established polymerization methodologies. The metal atoms reside as part of the macromolecular backbone, in sidechains, coordinated to the backbone, and as integral parts of dendrites, stars, and rods. Truly, many of tomorrow s critically important materials will have metal atoms as an integral part of the polymer framework, which will allow the materials to function as demanded. 

This chapter describes the synthesis and properties of a number of classes of polymers containing metal coordination complexes in their structures. These polymers are prepared by polymerization reactions of metal-containing monomers and through metal coordination reactions. Schiff base-containing polymers (5) were one of the earUest classes of coordination polymers examined. Polymers incorporating macro-cycUc porphyrins and phthalocyanines (7) in their backbones and sidechains are known to exhibit interesting optical and electrical properties. The best-studied classes of metal-containing polymers contain bipyridyl and other related units coordinated to metal ions (8). 

Many of these systems employ charged polymers or polyelectrolytes that confer on them particular properties due to the existence of electrical charges in the polymer structure. Oyama and Anson [14,15] introduced polyelectrolytes at electrode surfaces by using poly(vinylpiridine), PVP, and poly-(acrylonitrile) to coordinate metal complexes via the pyridines or nitrile groups pending from the polymer backbone. Thomas Meyer s group at North Carolina [16, 17[ also employed poly(vinylpyridine) to coordinate Ru, Os, Re and other transition-metal complexes by generating an open coordination site on the precursor-metal complex. 

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