Macromolecular metal complexes applications

The interaction of artificial metal ions/complexes with peptides/proteins [11], nucleic acids/DNA [12,13], enzymes [14], steroids [15] and carbohydrates [16] forms a bridge between natural and artificial macromolecular metal complexes. Biometal-organie chemistry concentrates on such complexes [17]. The reason for the increasing interest in this field lies in medical applications of metal complexes (cancer, photodynamic therapy of cancer, immunoassays, fluorescence markers, enantioselective catalysis, template orientated synthesis of peptides, etc.). Figure 2-4 presents an overview of metals in medicine [18]. Some examples are given below. 

The application of catalytic systems based on macromolecular metal complexes is one of the attractive lines of development of metal complex catalysis [1-7]. The use of macromolecular fragments in a metal complex catalyst enables one to substantially change the microenvironment of the catalytic site and, thereby, the catalytic properties of the metal complex. The main role in such a change (as, for example, in enzymes) is played by the submolecular structures formed by macromolecular metal complexes. These structures can selectively bind the substrate, alter the geometry and the energy of the transition state and cause mutual activation of the participants in the cataMic reaction [1]. 

Unfortunately, the aforementioned problems have not been adequately discussed in literature, although there is considerable interest in the preparation of structurally homogeneous macromolecular metal complexes for catalysis, photochemistry, biological applications, etc. This chapter reports on the specificity of the processes for formation of macromolecular complexes through both routes polymerlike transformations and copolymerization of metal-containing monomers. In addition, the predictive potential of reactions and the ways of preventing some of them will be discussed. 

Another attractive line of application of macromolecular complexes as catalysts is the so-called fluorous catalysis, whose idea was proposed in the early 1990s [163-168]. The main idea of such catalysis is that a catalyst is soluble (immobilized) in the perfluorocarbon phase, whereas the product is soluble in an organic solvent. If a suitable solvent for substrates, e.g. toluene or benzene, is used, then the system at sufficiently high temperature is homogeneous, and on cooling, there is phase separation. As a result, the solution of the metal complex in fluorocarbon is readily separable from the reaction products and can be reused. 

It should be mentioned that simple metal complexes immobilized on polymer supports were initially used for polymerization (1965/1966) in the Solvay catalysts based on titanium complexes bound to macromolecular ligands with C=0, C=N and C=N groups. Until now the data are mainly available in patent literature, and there are few kinetic studies of polymerization processes involving the action of macromolecular complexes. At the same time the use of metal complexes bound to inorganic supports has been extensively developed in polymerization catalysis. This indicates that there has been inadequate study of the application of metal complexes immobilized on polymer supports to the catalysis of polymerization and copolymerization of different monomers, mainly olefins. 

In this chapter we present an overview of this increasingly active research field. The first section focuses on coordination polymerization with metal complexes, classified by the nature of their ancillary ligands. The spectacular achievements reported recently in organocatalyzed and stereocontrolled ROP are then presented. The third section concerns the macromolecular engineering of poly(a-hydroxyac-ids) by varying both their substitution pattern (with alternative monomers to lactide and glycolide) and their architecture (via block, star and dendritic copolymers). The well-established and rapidly emerging applications of these synthetic polyesters are discussed briefly in the last section. 

This volume of the series focuses on the photochemistry and photophysics of metal-containing polymers. Metals imbedded within macromolecular protein matrices form the basis for the photosynthesis of plants. Metal-polymer complexes form the basis for many revolutionary advances occurring now. The contributors to many of these advances are authors of chapters in this volume. Application areas covered in this volume include nonlinear optical materials, solar cells, light-emitting diodes, photovoltaic cells, field-effect transistors, chemosensing devices, and biosensing devices. At the heart of each of these applications are metal atoms that allow the assembly to function as required. The use of boron-containing polymers in various electronic applications was described in Volume 8 of this series. 

Membrane processes, such as reverse osmosis and dialysis, are already used for certain effluent treatment applications and desalination. They can be operated continuously, and they allow recovery of the dissolved values. Membrane processes have benefited enormously from recent advances in membrane materials that can withstand high-pressure gradients and harsh chemical environments. Ultrafiltration of macromolecular complexes of metal ions, which shows more chemical specificity, was more promising for detoxifying effluents, and the work is still ongoing. Particulate matter, which is present in many environmental and processing solutions, can dramatically reduce the permeability of... 

The application of polymer-supported catalysts has now been extended to the synthesis of complexes between transition metal derivatives and structurally ordered macromolecular ligands to give catalytic systems exhibiting high activity and stereoselectivity. Polystyrene and polymethacrylate resin and polystyrene-divinylbenzene-polystyrene-polybutadiene block copolymers, as well as vinyl-functionalized polysiloxanes grafted onto silica, are very suitable polymers for heterogenization of mostly Pt and Rh complexes. Moreover, polyamides exhibit much higher thermal stability than conventional polystyrene supports (114). 

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