Polymerization copper complexes

On the other side, a totally insoluble cross-linked Schiff-base complex was prepared as follows. The glycidyl ether of bisphenol A was reacted with a Schiff-base chelate (prepared from 2,4-dihydroxybenzaldehyde and 1,3-diaminopropane followed by metallation) in a molar ratio of, for example, 6 1 at 150-200 °C to obtain the polymer 4 as shown in Eq. 6-3 (see Experiment 6-1, Section 6.6) [19]. Polymeric copper complexes in particular exhibit good thermal stabilities and good mechanical properties such as tensile strength. 

Further interesting redox modified polypyrrole films were prepared e.g. a polymeric copper phenanthroline complex that can be reversibly de- and re-metallated because it retains the pseudotetrahedral environment after decomple-xation, A very diversified electrochemistry is displayed by polypyrrole films containing electron donor as well as electron acceptor redox centers in the same film... 

Indeed, the above results seem to point toward a free radical mechanism. Sen and coworkers [60] studied a model copper complex (Fig. 13) and concluded that the polymerization proceeds via a free radical mechanism (Scheme 7) and that the copper complex/MAO system is in fact a new example of a redox free radical generator, in which the role of MAO is to reduce copper(II) to copper completing the redox cycle. This rationale also offers a simple explanation for the observation that very high excesses of MAO are required for the ethylene/acrylate copoly -... 

Keywords Atom transfer radical polymerization, ATRP, Copper complexes, Mechanistic understanding, Structures... 

ARGET ATRP has been successfully applied for polymerization of methyl methacrylate, ft-butyl acrylate and styrene in the presence of Sn(EH)2 (10 mol% vs. alkyl halide initiator or 0.07 mol% vs. monomer) [164,165]. For all monomers, polymerizations were well controlled using between 10 and 50 ppm of copper complexes with highly active TPMA and Me6TREN ligands. ARGET ATRP has also been utilized in the synthesis of block copolymers (poly(n-butyl acrylate)— -polystyrene and polystyrene-Z -poly(n-butyl acrylate) [164,165] and grafting... 

In the following sections we shall discuss (i) the structure and behaviour of the various copper complexes with the ligands listed in scheme 2 (ii) the activities of the polymeric catalysts in comparison with the low molecular weight analogs (iii) the effect of the degree of substitution, a, on the activities of the polymeric catalysts. 

A chiral amino-acid/copper complex is bound to a silica- or polymeric stationary phase and copper ions are included in the mobile phase to ensure there is no loss of copper. Amino acids then may be separated by the formation of diastereomeric copper complexes. Water stabilizes the complex by coordinating in an axial position. Steric factors then determine which of the two complexes is more stable. One of the water molecules is usually sterically hindered from coordinating with the copper. i ... 

Selective polymerization, enantiomers, 185 Semico rrin-copper complexes, 199 Sharpless epoxidation, racemic alcohols, 45 Side-chain units, prostaglandins, 310 Sigmatropic reactions, 222 Silanes, oxidative addition, 126 Silica gel, 285, 352... 

Involvement of two nucleophilic nitrogen atoms is thus typical for the amino heterocycles. The mutual disposition of the pyridine and amine nitrogen atoms allows the formation of chelate structures for the cobalt complexes of purine, 221 and 222. Structures with the N, iV -five-membered metal cycles were proven for the tri- and tetranuclear complexes of silver ) with 8-aminoquinoline (223) (92IC4370), and polymeric copper- and rhodium-acetate clusters (224). Another coordination mode can be found in the complexes of 4-amino-3,5-bis(pyridin-2-yl)-l,2,4-triazole, (225 or... 

Gardiner and Casey [65] observed the radicals Of, Of, and MOf, which are formed on various electrode surfaces during oxidation processes on different materials in KOH solutions. Studies of copper dissolution in pyrophosphate [66] resulted in polymeric copper pyrophosphate complexes. 

Copper-catalyzed oxidations of phenols by dioxygen have attracted considerable interest owing to their relevance to enzymic tyrosinases (which transform phenols into o-quinones equation 24) and laccases (which dimerize or polymerize diphenols),67 and owing to their importance for the synthesis of specialty polymers [poly(phenylene oxides)]599 and fine chemicals (p-benzoquinones, muconic acid). A wide variety of oxidative transformations of phenols can be accomplished in the presence of copper complexes, depending on the reaction conditions, the phenol substituents and the copper catalyst.56... 

Oxidative coupling polymerization provides great utility for the synthesis of high-performance polymers. Oxidative polymerization is also observed in vivo as important biosynthetic processes that, when catalyzed by metalloenzymes, proceed smoothly under an air atmosphere at room temperature. For example, lignin, which composes 30% of wood tissue, is produced by the oxidative polymerization of coniferyl alcohol catalyzed by laccase, an enzyme containing a copper complex as a reactive center. Tyrosine is an a-amino acid and is oxidatively polymerized by tyrosinase (Cu enzyme) to melanin, the black pigment in animals. These reactions proceed efficiently at room temperature in the presence of 02 by means of catalysis by metalloenzymes. Oxidative polymerization is observed in vivo as an important biosynthetic process that proceeds efficiently by oxidases. 

Kinetically slow steps in the formation of melanin from DOPA are the formation of dopaquinone from DOPA (step 1, kD), the reaction of dopachrome to dihydroxyindole (step 2), and the polymerization to form melanin (step 3, kM). Step 1 and step 2 proceed with about the same rate in the oxidative coupling polymerization catalyzed by tyrosinase. However, step 1 becomes remarkably slow when a macromolecule-metal complex is used as a catalyst. The copper complex in poly(l-vinylimidazole-co-vinylpyrrolidone) has been found [38] to act as an excellent catalyst and to exhibit the highest activity for melanin formation. The ratio of the rate constants ( m/ d) is approximately 3 (tyrosinase... 

Dimethylphenol is oxidatively polymerized to poly(2,6-dimethyl-1,4-phenyl-ene ether) with a copper-amine complex by a laccaselike reaction. The activated phenols are coupled to form a dimer. The dimer is activated by a mechanism similar to that by which the polymerization proceeds. The effects of the amine ligands are to improve the solubility and the stability of the copper complex as well as the phenol-coordinated complex and to control the redox potential of the copper complex. 

Electron transfer from the substrates to 02 proceeds by a redox cycle that consists of copper(II) and copper(I). The high catalytic activity of the copper complex can be explained as follows (1) The redox potential of Cu(I)/Cu(II) fits the redox reaction. (2) The high affinity of Cu(I) to 02 results in rapid reoxidation of the catalyst. (3) Monomers can coordinate to, and dissociate from, the copper complex, and inner-sphere electron transfer proceeds in the intermediate complex. (4) The complex remains stable in the reaction system. It may be possible to investigate other catalysts whose redox potentials can be controlled by the selection of ligands and metal species to conform with these requisites several other suitable catalysts for oxidative polymerization of phenols, such as manganese and iron complexes, are candidates on the basis of their redox potentials. 

Recent research reveals that the oxidative polymerization of phenol with 02 also obeys the multielectron transfer with the polynuclear copper complexes [74], The multielectron oxidation of substrates provides new active species,... 

A similar mixed ox a- thia macrocycle incorporating a rigid horseshoeshaped aromatic moiety, l,ll,21-trioxa-8,14-dithia[2,9,2]paracyclophane, L40, has been synthesized and reacted with copper iodide in MeCN solution (Scheme 19).160 Its polymeric copper iodide complex [Cu4I4(L40)2] 40 crystallizes, in a 2 1 metal to ligand ratio, as an ID infinite array of cubane-like units consisting of four copper atoms, four i3-iodine atoms, and four sulfur atoms, stemming from four different macrocycles. The Cu—Cu distances are about 2.731 A. Unfortunately, the photophysics of this compound have not been studied. 

Most reported phthalocyanine derivatives (sulfo-, nitro-, amino-, triphenylmethyl-, polymeric, etc.) are copper complexes, although at present the synthetic chemistry of other d- and /-metal Pc derivatives is being rapidly developed (Examples 30-36) [5,6,116-118]. Some of them (in particular, copper phthalocyanine sulfonic acids) are of industrial interest because of their usefulness as dyes. Phthalocyanine sulfonic acids themselves are prepared both by urea synthesis from sulfonated phthalic anhydride and by the sulfonation of the phthalocyanine [6], Some substituted metal phthalocyanines can be obtained by chemical or electrochemical reduction [118e]. Among a number of reported peculiarities of substituted phthalocyanines, the existence of three electronic isomers for magnesium derivative PcMn was recently confirmed [118f]. 

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