Self metal-mediated

A review13 with 53 references of the transition-metal mediated supramolecular self-assembly is presented. Focus is on the self-assembly of macrocycles, catenanes, and cages from (en)Pd(N03)2 and pyridine-based bridging ligands. 

Figure 87 A host cage, constructed through transition metal mediated self-assembly from six metal ions and...

Stang, P. J. Olenyuk, B. Transition-metal-mediated self assembly of discrete manoscopic species with well-defined structures and shapes. In Handbook of Nanostructured Materials and Nanotechnology, Nalwa, H. S.. Ed. Academic Press San Deigo, 2000, Vol. 5, 167-224. 

In the first case, the details of network build-up and modification of network structure described above are not very important. The main aim of crosslinking is to keep the dendritic structures together permanently. Formation of three-dimensional nanostructures by metal-mediated self-assemblage can serve as an example Exo-tridentate tripyridyl compounds self-assemble upon treatment with (en)Pd(N03)2 [66]. 

In the specific case of calixarenes, there are very few studies related to metal-mediated self-assembly into cage molecules. Early examples reported by Shinkai and coworkers include bis(acac)-calix[4]arene dimer (1) held together by Cu2+ cations... 

In this synthetic strategy, supramolecular interactions are used to construct the catalyst backbone. The approach can be used for a wide variety of catalysts, and mechanistic effects include catalytic supramolecular assemblies, self-assembly, metal-mediated catalysis and organocatalysis, and chiral induction. 

Both amine and lysyl oxidases possess a single Type 2 copper center and a redox-active cofactor per subunit. As shown in Figure 18, amine oxidases contain 2,4,5-trihydroxyphenylalanine quinone (TPQ) and lysyl oxidase contains lysyl tyrosine quinone (LTQ), in which a lysine side chain has been cross-linked to TPQ. These cofactors are produced from the oxidation of a specific active-site tyrosine residue via novel self-processing events that require only copper and O2 see Metal-mediated Protein Modification). 

Elucidating all the fascinating details of this reaction will require further mechanistic, structural, and model studies. Finally, the discovery of self-processing redox enzymes (see Section 6 see Metal-mediated Protein Modification) may be relevant to understanding aspects of the evolution of enzymes. Metal-ion mediated redox chemistry with oxygen can modify several amino acids, especially tyrosine, tryptophan, cysteine, and histidine. This may have provided a path to generate new redox cofactors prior to the advent of the complex biosynthetic pathways. 

Figure 8 Ring-and-strings self-assembly filamentous ligand (17) combines with cyclic ligand (18) to form pseudorotaxane [Cu(17)(18)]+ upon treatment with Cu1. Multiple-interaction self-assembly (uni-/metal-mediated) combining (17), (18), Cu1 and Ru11 generates the catenane (19).

Two main types of multiple-interaction self-assembly have been demonstrated 25 (i) those involving the formation of two or more different types of coordinate bonds (metal-mediated or... 

The metal-mediated synthetic approach has recently provided many examples of large discrete assemblies of porphyrins [39-41] and of solid-state arrays as well [39-48]. For the purpose of metal-driven synthesis, porphyrins and metal centers are to be considered essentially as rigid modules. Thus, in principle, the final shape, dimension, and topology of the self-assembled architecture will be defined by the number and relative geometries of the coordination sites on the building blocks. Within this framework, meso-pyridylporphyrins (PyPs, Fig. 1) are largely exploited as they can provide... 

The adduct [6Zn]2, that features four porphyrins and six metal atoms (two Ru and four Zn), is an imprecedented example of a discrete and highly ordered array of porphyrins obtained by two-point metal-mediated self-assembly. 

As discussed in Sect. 3, various multiporphyrin molecular boxes can be obtained that combine both external metal-mediated and side-to-face assembling motifs. The chemical structure of the molecular box 14, resulting from side-to-face self-assembling of two 9Zn metallacycles and two 4 -tra sDPyP units, is shown in Fig. 32 (for the X-ray structure, see Fig. 19). 

Fig. 3 Homo-polymers (a) and hetero-polymers (b and c) by metal-mediated porphyrin self-assembly...

An overview of the thermodynamic principles governing self-assembly in solution, with particular reference to multiporphyrin architectures, is presented by Gianfranco Ercolani in the fifth chapter. The topic is discussed in order of increasing complexity, from simple acyclic assembhes to multi-cyclic assemblies. The principles are illustrated by selected examples of metal-mediated assemblies of porphyrins, many of which have been described in the previous chapters. 

The production of supramolecular polymers containing chromium tricarbonyl and manganese tricarbonyl moieties was deseribed."" Sweigart recently reported the self-assembly of r -quinone and r -semiquinone complexes derived from hydroquinone coordinated to cationic manganese tricarbonyl moieties." The metal-mediated deprotonation of these complexes allowed for the pro-duetion of polymers such as 16. 

Stang. P.J. Olenyuk, B. Muddiman, D.C. Smith, R.D. Transition-metal-mediated rational design and self-assembly of chiral, nanoscale supramolecular polyhedra with unique T symmetry. Organometallics 1997. 16. 3094-3096. 

In this article, a brief and general review of catenanes in terms of their nomenclature, self-assembly, and a few pertinent properties will be presented. Examples of the concepts discussed were limited to representative transition metal-mediated processes. 

Illustrated in Fig. 2 is one of the most famous examples of a metal-mediated, thermodynamically self-assembled catenane. The reaction of 1 (M = Pd) with the angled bipyridyl ligand 2 was found by Fujita and coworkers to lead to the formation of cycle 3, along with the interlocked catenane The nature of the self-assembly process... 

The foniiation of 4, therefore, involved several different noncovalent interactions. The cyclization step was brought about by the formation of Pd—N coordinate bonds that is, by a metal-mediated process. The interlocking step involved n- and hydrophobie/hydrophilic-mediated processes, along with an entropic effect. Catenane 4 can. therefore, be considered an example of a multi-mediated,"" multiple-interaction self-assembly. Fujita referred to such processes as ""double-molecular recognition"" procedures, in which the two interlocking molecules bind each other in their cavities. 

While the simultaneous use of several different classes of noncovalent interactions provides an elegant means of preparing a catenane. such systems are not always easily designed. Another method of thermodynamically selfassembling catenanes involves using two or more metal-mediated interactions to carry out the cyclization and interlocking steps. Illustrated in Figs. 3 and 4 are examples of thermodynamic self-assembly of this type. 

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