Metallo-macrocycles

Architectural control of transition metal-directed assembly to construct well-arranged metallo-macrocycles is one of the current research areas to create organized nanostructures for advanced materials.510-513... 

Kay Severin s group has previously investigated the preparation of dynamic combinatorial libraries of metallo-macrocycles for use as sensors for Li+ at physiologically relevant conditions [59]. For example, they have found that ligand 62 and metal complexes 63 undergo a self-assembly process to yield the trimeric complexes depicted in Scheme 4.15 [60]. Mixtures of 64 and... 

The chemical flexibility of the porphyrin-like metallomacrocycles has been used to vary the electronic properties of the molecular units and hence the resulting solid. This has been brought about by the choice of the basic ligand, the peripheral substituents and the central metal. The main variants on the porphyrin skeleton are shown in Figure 8. A large number of compounds have been obtained as conducting polycrystalline powders by oxidation of the parent metallo-macrocycle with iodine.90 Table 4 contains details of compounds which have been obtained as single crystals and have been extensively characterized and studied. 

MePOR species and other complexes in cationic clays can be located at the edges of packed platelets, in the interlamellar space or in the mesopores present (Scheme 10.9). A review of the early data in this area is available.[86] The flat metallo macrocycles under clay synthesis conditions help to induce layer silicate formation, the complexes being intercalated between the layers. Whereas with monooxygen atom donors, alkanes can be oxygenated with significantly enhanced activities compared with the homogeneous case, in every case the expected products (ol/on) were obtained. Competitive oxygenation of adamantane and pentane shows lower... 

The general structure of the polymers is shown below (the square represents the macrocycle and L is the diisocyanide bridging ligand), and their syntheses involve reacting a given metallo-macrocycle with a desired bridging ligand. The polymer precipitates due to relatively weak solubility, and characterization is often limited to the solid state. 

Chiral Metallo-macrocycles with Organometallic Half-sandwich Complexes... 

Several groups have investigated the synthesis of such compounds, for instance the cationic metallo-macrocycles [(t -ring)M(Aa)]3[BF4]3 (Aa = amino acidate) act as catalysts for hydrogen transfer to ketones while the neutral metallo-macrocycles [( -ring)ML]3 are efficient hosts for alkali metals (Li and Na). However, the chiral aspect of these species in solution was not investigated and only Yamanari and coworkers have reported diastereomeric separations, but no NMR studies have been made to differentiate these chiral macrocycles by the use of a chiral auxiliary. Recently the chemistry of these macrocycles was reviewed by Severin, who contributed largely to the development of this field. 

Self-assembly of chiral metallo-macrocycles using trifunctional assembling mono-anionic and dianionic ligands. 

It is worth noting that the chiral metallo-macrocycles assembled with these angular bipyridine ligands were less robust than the previous ones formed from the strong Pt-alkynyl linkage. This is due to the lability of the M-pyridyl bonds. 

When the reactive chiral building unit [M(/ -(+)-BINAP)(H20)][0Tf]2 with M = Pd (5.84) or M = Pt (5.85) was treated with the bridging ligand bis [4-(4 -pyridyl)phenyl) iodonium triflate (57), the related chiral hybrid supramolecular squares were formed (5.86-5.87) (hybrid = presence of iodonium and transition metal comers in the assembly). These hybrid molecular squares are optically active due to the chiral transition metal auxiliary (BINAP) in the assembly. Interestingly chiral induction was observed in these metallo-macrocycles since the preferred diastereomer in each preparation was formed in excess compared with the other isomers (Figure 5.34). ... 

Maekawa and Kitagawa have recently reported an interesting anion-directed approach to the synthesis of bowl-shaped metallo-macrocycles [27]. Initially, they observed that the reaction between [Cu(MeCN)4](PF6) and 4-(2-pyridyl)pyrimidine (pprd) under an atmosphere of C2H4 and in acetone yielded the coordination polymer [Cu(pprd)(C2H4)](PF6) (see Scheme 4). 

Scheme 10 Reaction scheme showing the anion-directed synthesis of metallo-macrocycles and their interconversion...

Scheme 13 Reaction scheme for the synthesis of metallo-macrocycles 33 and 34...

Scheme 14 Reaction scheme showing the equilibrium between the [2+2] and [3+3] metallo-macrocycles...

Redox switching of anthracene fluorescence by an appended metallo-macrocycle subunit... 

In the following we will discuss some unconventional properties of macrocyclic metal complexes, preferentially semiconductive and liquid crystalline behavior. There are several reviews available on low-dimensional conductive compounds based on these macrocycles [21]. A detailed description of newer developments in the field of bridged macrocyclic metal complexes especially with transition metals was published recently [22]. In order to use the 7t-electrons in these macrocyclic systems for a conduction pathway, polymerization of the metallo-macrocycles is necessary. A polymerization can be carried out in three different ways as explained in Sections 1.2.1-1.2.3. 

Although metallo-macrocycles are generally unlikely to maintain their original structure after the heat treatment [29], that original structure before the treatment is important as it often affects final distribution of atoms in the catalysts and its... 

Figure 3.34 (a) The eight components and (b) the crystal structure of a catenane consisting of two metallo-macrocycles. The void with one cyclic species is an ideal size/shape fit for another copy of itself to fill. 

In 1995, Hamilton et al. described one of the first examples of a combinatorial approach to synthetic receptors using reversible coordination around a metal ion [20]. In the same year Harding et al. described the guest-induced amplification of a metallo-macrocycle 4 and metaUo-[2]catenane 5 from a mixture (Scheme 1.4) [20, 21]. Although not described as such, these examples employed the basic principles of DCC-template-stabilized selection of effective synthetic receptors from among an equihbrating library of potential receptors. 

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