Polymers metal-binding sites

The ion channels which permit transport of ions, are constructed from protein polymers in helical conformations. These helices form the wall of cell channels and their precise conformations result in specific geometrical arrangements of a number of potential ligand-metal binding sites. There are striking differences between the channels, selective towards either Na+ or K+ ions. 

Clearly, if metal-binding sites are required, one strategy is to prepare alternating copolymers where one monomer is based on a well-known ligand (e.g., bipyridine, phenanthroline, and acetylacetonate), which is capable of coordinating to a metal ion. One such example was a study carried out by Liu et al. In this case, three similar conjugated polymers 17 (R = Oct), 18, and 19 based on fluorene and bipyridine were prepared and tested for their metal ion sensing capabilities [55],... 

Type II polymers with pendant metal complexes Polymers containing bipyridyl and terpyridyl metal-binding sites... 

In a related work, a design of enzyme-inspired star block-copolymers with branched topologies and protein-Hke tertiary or quaternary structures was performed. These polymers incorporate hydrophihc, superhydrophobic, and polydentate metal-binding sites and self-assemble in water, their mode of assembly being controlled by the composition of the polymer. An important feature of the star block-copolymers is that they incorporate perfluorocarbons and, due to that, their emulsions in water can attract and preconcentrate O2 in the vicinity of the active metal site. Addition of Cu(II) and TEMPO leads to an effective catalytic system for oxidation of alcohols to aldehydes in water. " ... 

Molecularly imprinted polymers (MIPs) can be prepared according to a number of approaches that are different in the way the template is linked to the functional monomer and subsequently to the polymeric binding sites (Fig. 6-1). Thus, the template can be linked and subsequently recognized by virtually any combination of cleavable covalent bonds, metal ion co-ordination or noncovalent bonds. The first example of molecular imprinting of organic network polymers introduced by Wulff was based on a covalent attachment strategy i.e. covalent monomer-template, covalent polymer-template [12]. 

Preconcentration of metal cations is also achieved by providing ligand binding sites in polymer layers, e.g. 4-methyl-4 -vinyl-2,2 -bipyridine for Fe " and Cu ". Carbon paste electrodes containing dimethylglyoxime or o-phenanthroline... 

With these features in mind, we envisioned a new family of macrocyclic ligands for olefin polymerization catalysis (Fig. 9) [131, 132], We utilized macrocycles as the ligand framework and installed the catalytic metal center in the core of the macrocycles. Appropriate intra-annular binding sites are introduced into cyclophane framework that not only match the coordination geometry of a chosen metal but also provide the appropriate electronic donation to metal center. The cyclophane framework would provide a microenvironment to shield the catalytic center from all angles, but leaving two cis coordination sites open in the front one for monomer coordination and the other for the growing polymer chain. This could potentially protect the catalytic center and prevent it from decomposition or vulnerable side reactions. 

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