Macroligands, chelating

Star structures can be performed by the combination of coordination chemistry with living or controlled polymerization via metalloinitiation, metallotermination, coupling, or macroligand chelation approaches (Scheme 65). 

Figure 2. (A) Macroligand chelation and (B) metalloinitiation approaches to metal complexes with bipyridine polyester macroligands.

For another illustration of macroligand chelation see Peter, K. Thelakkat, M. Macromolecules 2003. 56, 1779-1785. 

Macromolecular metal complexes can be classified into three main categories, taking into consideration the manner of binding of a metal compound to suitable macroligands [33] (Fig. 1). Type 1 metal complexes are those with the metal ion or metal chelate at a macromolecular chain, network, or surface. One possible approach to synthesize such polymers is using the polymerization of vinyl-substituted metal complexes. 

Johnson RM, Fraser CL. Iron tris(bipyridine)-centered star block copolymers chelation of triblock macroligands generated by ROP and ATRP. Macromolecules 2004 37 2718-2727. 

Main Approaches to Calculating the Equilibrium Constants in Metal Ion — Chelating Macroligand Systems... 

The assessment of the chelating ability of macroligands and applicability of such systems requires the data on the quantitative evaluation of the chelation processes such a stability constants and formation function. Contemporary methods are largely based on the composition of the products formed. The major methods of analyzing the quantitative parameters of MX chelation use predominantly the same techniques that are applied to the description of complexing reactions with participation of monofunctional macroligands [5, 7b, 13a]. 

Considering the three levels a change of the free energy when chelation involves macroligands (assuming its additivity) is as follows ... 

The application of such techniques to high-molecular weight compound chemistry is complicated by problems involved in the synthesis of the corresponding macroligands. Among the examples which are few in number is the production of binuclear Co (II) and Ni(II) chelates based on PE-g-poly (iV-salicyloylacryl-amide) [15, 22d] ... 

It should be noted that PCMU based on cross-linked macroligands possess a relatively high chemical and thermal stability. The stability of poly(enol-ketonate) chelates obtained by oxidation of thin polyvinylacetate films increases in the series of mono-, di- and trivalent ions [122], the oxidation promoting the penetration of the metal ions into the deep film layers. The weight loss of Co and Mn polychelates based on the condensation products of stoichiometric amounts of 5,5 -methylene-bis-salicylaldehyde and 4,4 -diaminophenyl ether at 300, 500, and 600 °C is 2.1, and 0.5 8.0 and 9.8 25.0 and 27.5%, respectively [14b]. The stability, in the range between 275 and 640 °C, of chelates formed by the transition metals and condensation products of p-hydroxybenzoic acid, urea and formaldehyde follow the series [123] Fe(III)>Co(II)>Cu(II)>Ni(II)>V02(II)> Zn(II) Mn(II) > CML. 

Initially, Ln PMCs were synthesized in a mixed solvent system consisting of acetone, CH2CI2, and MeOH to accommodate both die metal salt and macroligands. More recently, it has been found that THF can be used as a solvent for the chelation reaction, simplifying the synthesis. By varying the equivalents of macroligand in the reaction mixture, both tris or tetrakis Eu dbm complexes can be targeted. 

Monomers of metal complexes/chelates suitable for polymerizations, and also polycondensations or polyaddition reactions, can be employed successfully for the preparation of metal containing polymers. In most cases polymerizations are carried out in the presence of a comonomer to obtain polymers with sufficient solubility. For polymerizations either a vinyl group containing ligand is polymerized followed by introduction of a metal ion in the macroligand, or the vinyl group containing metal complex/chelate is directly converted into the MMC. In some cases when chain transfer due to a transition... 

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