Macrocycle-based metal containing

Metalated container molecules can be viewed as a class of compounds that have one or more active metal coordination sites anchored within or next to a molecular cavity (Fig. 2). A range of host systems is capable of forming such structures. The majority of these compounds represent macrocyclic molecules and steri-cally demanding tripod ligands, as for instance calixarenes (42), cyclodextrins (43,44), and trispyrazolylborates (45-48), respectively. In the following, selected types of metalated container molecules and their properties are briefly discussed and where appropriate the foundation papers from relevant earlier work are included. Porphyrin-based hosts and coordination cages with encapsulated metal complexes have been reviewed previously (49-53) and, therefore, only the most recent examples will be described. Thereafter, our work in this field is reported. 

Recently, several groups reported molecular squares prepared by an alternative approach, in which bifunctional metalloligands serve as the linkers thereby placing the metal ions into the walls of the container molecules (114—116). Hupp and coworkers, for example, have designed square-shaped macrocycles based on salen-type components (117). Thus, the molecular square 15 was prepared by the directed assembly of cis- [(PEt3)2Pt(OTf)2] and... 

Polymers have served roles in PEM fuel cell cathodes such as modifiers to macrocycle-based electrodes to improve conductivity and stability,165 composite materials with heteropolyacids,166 and as precursors to pyrolyzed catalysts.38,112,132,133 However, as discussed in the previous section, the activity of nitrogen-containing carbon raises the possibility of non-metal electrodes functioning in a cathode environment. Likewise, researchers have noted ORR activity for various conducting polymers containing nitrogen, and recently studies on their potential use in PEM fuel cell cathodes have been reported. 

A different approach is the metal-based template method [2cj, 10], for example starting from a wire (11) and a macrocycle (12), both containing a phenanthroline unit, and using Cu+ as a template (Figure 3c) [2cj. Species of this kind are essentially metal complexes, and may have very large formation constants. 

Thiophene aldehydes have been used earlier for the construction of macrocyclic Schiff bases <81CC628>. An example is the synthesis of the macrocyclic tetraimine Schiff base (479) from thiophene 2,5-dicarbaldehyde and l,3-diamino-2-hydroxypropane <87JCS(D)219>. The synthesis does not involve use of a metal template. An interesting extension is the synthesis of the macrocyclic Schiff base (481) containing four thiophene units from the dialdehyde (480) <89BCJ1346>. The condensation is achieved at room temperature in CHCI3. 

While the types of MCMs described earlier have already received comparatively wide popularity in polymerization practice, polymers based on metal-containing monomers of the chelate type have only been prepared more recently. The methods of assembly of such MCMs, i.e. the simultaneous formation of the ligand and the corresponding complex, have been substantially developed. The synthesis of MCMs from /7-aminostyrene, 2-formylpyrrole and Cu(II) or Co(III) salts is an example of such a method. The last approach is especially characteristic of the preparation of MCMs with macrocyclic chelate nodes, in particular, from porphyrins, phthalocyanines and other macrocycles with exocyclic multiple bonds. It is worth noting that traditional methods of chelation are used for preparing MCMs when scientists want to ensure strong multicenter fixation of metals into monomer molecules, and, thus, into (co)polymers. 

Catalytic Chain Transfer. A highly useful variant of chain transfer was discovered in the 1970-1980s in the Soviet Union (216). A number of reviews have been published in recent years (217-221) on this synthetic method which has acquired the nomenclature of either catalytic chain transfer (CCT) or special chain transfer (SCT). The most commonly adopted catalysts are based on low spin cobalt macrocycles, although other metal-containing complexes have also been suggested in the patent and scientific literature. Some typical catalyst structures are shown as 12 and 13. 

The macrocyclic Schiff base L37 contains an hexyl linker between the two amine groups. In anion transport experiments, the corresponding metal complexes of L37 are found to successfully extract sulfate anion from aqueous solution to organic solvents. In the case of the copper complex of receptor L37, it was found that more than... 

Threading of the phenanthroline-based macrocycle 88 onto either the bipyridine- or the phenanthroline-based bis-thiophene derivatives 86 and 87, respectively, occurs [180-182] (Fig. 23) spontaneously in the presence of metal ions (Zn + or Cu ) which can be coordinated tetrahedrally. Electropolymerization of the resulting metal-containing pseudorotaxanes afforded the metal-containing pseudopolyrotaxanes 89 and 90. The decomplexation/complexation of ions can be achieved reversibly in the case of 89. By contrast, the reinsertion of Cu+ ions into 90 is only possible when the demetalation is performed in the presence of Li+ ions which prevent the collapse of the polymer by coordinating with the phenanthroline units. The redox and conducting properties of 89 are affected dramatically by the coordinated metal ions that produce charge localization and participate in conduction by means of redox processes. 

A number of dithiocarbamates derived from diamines have been prepared, including those based on a terphenyl backbone, which have utilized these ligands toward the self-assembly of large metal-containing macrocycles upon addition of metal acetates (1468,1469). For example, macrocyclic complexes (347) have been prepared in this manner. 

Strange enough, so far there are no books entirely devoted to condensation TPEs and the latter are considered only in chapters of more general works. The most important TPEs prepared by polycondensation are the subject of several chapters of this book polyester-based TPEs, poly(amide-6-ethers), polyurethanes, etc. However, some less known condensation TPEs are described in Chapter 2 metal-containing macrocycles as monomers, liquid crystalline side chains, metallo-supramolecular block copolymers, as well as the use of enzymatic catalysis or of microorganisms. 

Since the phosphorus atoms of these macrocycles are all included in phosphole rings, they readily invert close to room temperature. The macrocycles 195-197 can therefore adopt their conformations to the stereochemical requirements of the complexed metals. Macrocycles 195 and 196 can chelate either one (198) (M = Mo(CO)4 [166], PdCb [167]) or two (199-200) (M = Mo(CO)4 [166]) metal-containing units via their diagonal phosphorus atoms. The structure of the cage complex 200 shows a Mo-Mo distance of 5.883 A [166]. Life-times of the palladium catalyst based on the cyclophane ligand 195 in Stille cross-coupling and Heck reactions demonstrate extraordinary resistance of the catalyst towards degradation [167]. 

Over the last decade, the chemistry of the carbon-carbon triple bond has experienced a vigorous resurgence [1]. Whereas construction of alkyne-con-taining systems had previously been a laborious process, the advent of new synthetic methodology based on organotransition metal complexes has revolutionized the field [2]. Specifically, palladium-catalyzed cross-coupling reactions between alkyne sp-carbon atoms and sp -carbon atoms of arenes and alkenes have allowed for rapid assembly of relatively complex structures [3]. In particular, the preparation of alkyne-rich macrocycles, the subject of this report, has benefited enormously from these recent advances. For the purpose of this review, we Emit the discussion to cychc systems which contain benzene and acetylene moieties only, henceforth referred to as phenylacetylene and phenyldiacetylene macrocycles (PAMs and PDMs, respectively). Not only have a wide... 

Perspectives for fabrication of improved oxygen electrodes at a low cost have been offered by non-noble, transition metal catalysts, although their intrinsic catalytic activity and stability are lower in comparison with those of Pt and Pt-alloys. The vast majority of these materials comprise (1) macrocyclic metal transition complexes of the N4-type having Fe or Co as the central metal ion, i.e., porphyrins, phthalocyanines, and tetraazaannulenes [6-8] (2) transition metal carbides, nitrides, and oxides (e.g., FeCjc, TaOjcNy, MnOx) and (3) transition metal chalcogenide cluster compounds based on Chevrel phases, and Ru-based cluster/amorphous systems that contain chalcogen elements, mostly selenium. 

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