Preformed polymers, metal coordination

Such bilayers can conveniently be built up by successive electropolymerization of complexes containing ligands with vinyl substituents, e.g. 4-vinylpyridine or 4-vinyl-4 -methyl-2,2 -bipyridyl. The films may be deposited on metallic or semiconductor electrodes (e.g. Pt, glassy carbon, Sn02, Ti02). More efficient metailation of the films is obtained by polymerization of coordinated ligand than by subsequent metailation of a preformed polymer film. An alternative to discrete films would be a copolymer with distinct redox sites, or a combination of a single polymer film with a copolymer film in a bilayer device. 

Initial research into the application of PMEs focused on their potential use in electrocatalysis. Much of this work centered on preformed redox polymers containing coordinated electroactive metal complexes because of the synthetic flexibility and the ability to control loading of the electrocatalytic center in the modifying layer. Electrostatic binding of electroactive ions into ionomeric polymer films is a convenient procedure for preparing electrocatalytic layers, although care must be taken to minimize leaching of the electroactive center. ... 

Many researchers have focused on the preparation and catalytic properties of polymer-bound ruthenium and osmium species because of their proven ability to catalyze homogeneous reactions and the vast synthetic chemistry available for their preparation. A series of preformed polymers of [M(bpy)2(pol)nCl]Cl, where M can be a Ru(II) or Os(II) metal center coordinated to 2,2 -bipyridine ligands (bpy) and anchored to a pyridine or imidazole nitrogen of a PVP or poly(N-vinylimidazole) polymer (pol), have been prepared and characterized with respect to charge transport rates and mechanisms in drop-coated films on electrode surfaces. Electrodes coated with films of the ruthenium polymer have been shown to mediate the oxidation of nitrite, and nickel bis(2-hydroxyethyl)dithiocarbamate. ... 

There are two different ways in which metal coordination can yield a metal-containing polymer. The first methodology involves the coordination of metal complexes to preformed polymeric materials. This is illustrated in Scheme 12 by the coordination of a ruthenimn complex (94) to the bipyridine hgands along the backbone of polymer 93. This coordination reaction resulted in the formation of the corresponding ruthenimn polymer 95. ... 

Coordination polymers can be prepared by a number of routes, among which the three most common being (1) preformed coordination metal complexes polymerized through functional groups where the actual polymer-forming step may be a condensation or addition reaction ... 

Similarly, this amphiphilic polymer micelle was also used to dismpt the complex between cytochrome c (Cc) and cytochrome c peroxidase (CcP Sandanaraj, Bayraktar et al. 2007). In this case, we found that the polymer modulates the redox properties of the protein upon binding. The polymer binding exposes the heme cofactor of the protein, which is buried in the protein and alters the coordination environment of the metal. The exposure of heme was confirmed by UV-vis, CD spectroscopy, fluorescence spectroscopy, and electrochemical kinetic smdies. The rate constant of electron transfer (fc°) increased by 3 orders of magnimde for the protein-polymer complex compared to protein alone. To establish that the polymer micelle is capable of disrupting the Cc-CcP complex, the polymer micelle was added to the preformed Cc-CcP complex. The observed for this complex was the same as that of the Cc-polymer complex, which confirms that the polymer micelle is indeed capable of disrupting the Cc-CcP complex. 

Figure 6. Preformed organic polymers combine with metal ions to produce coordination polymers...

There is little information on rates of initiation in coordination polymerization. With the soluble catalyst (7r-CsHs)2TiCl2—AlMejCl for ethylene, Chien [111] reported = 4.99 x 10 1 mole s at 15°C Ei = 15.5 kcal mole ). This was determined from the rate of incorporation of C14 labelled AlMe2 Cl into the polymer. In most systems examined the initiating centres have been preformed and reaction starts immediately. This is the case with Natta type catalysts from transition metal subhalides with the alkyls of aluminium, beryllium and zinc. With some catalysts the rate rises rapidly to a steady value but with others there is a rapid rise to a maximum followed by a decline to a constant rate, the latter being... 

Polymers 250 and 251, formed by coordination of Ru11 complexes to the preformed 2,6-poly(bis(benzimidazol-2-yl)pyridine), showed a strong enhancement of absorption and photosensitivity in the visible region relative to the unmetalated polymer.141 The metalated polymers, with ca. 90% of the coordination sites occupied, showed an inherent viscosity of 1.8 dLg-1. Although the polymers have low conductivities (ca. 10 10Scm-1), they exhibited higher photocurrents than the organic precursor polymer. 

Coordination polymers can be prepared by preformed metal complexes polymerized... 

In addition to polystyrene, several other polymers have been provided with the hypercrosslinked structure, and, in addition to the postcrosslinking of preformed polymeric chains, other synthetic approaches to hypercrosslinked open networks have been developed, including the direct polymerization and polycondensation of appropriate monomers or co-monomers. The recently developed metal-organic frameworks and covalent organic frameworks constitute three-dimensional coordination and element-organic polymers with an unusually h%h free volume they fit into the new and rapidly growing class of hypercrosslinked network materials as well. 

There have been a considerable number of poly-rotaxanes reported in which the rotaxane motifs combine polymeric and discrete components. The most common of these involve preformed molecular rotaxanes acting as ligands, with the axle component containing coordinating groups at either end. Reaction of these rotaxane-based ligands with metals then gives polymeric structures. An example of a ID polymer constructed in... 

In this chapter, we highlight recent examples of the use of the mentioned click reactions as the macrocyclization reaction in several contexts. We exclude the following from the current review (i) cyclic structures in which part of the cyclic connection is formed by noncovalent bonds [26] (ii) the postmodification with CuAAC click chemistry of preformed macrocycles in order to introduce triazoles for functional applications [27, 28] and (iii) coordination polymers, or metal-organic frameworks, formed by clicked struts or ligands [29]. This chapter is structured in several subchapters according to the different classes of macrocycles obtained. 

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