Cage self-assembly

Scheme 7.3 Cage self-assembly using ethylene-bridged cavitands 10a,b.

An uncommon experiment of cage self-assembly in a liquid-liquid two-phase system has been described. Cavitand 31b (1 equiv) dissolved in 1,1,2,2-tetrachlor-oethane was exposed to an aqueous solution of Pd(en)(N03)2 (2.5 equiv) in a test tube. Immediately, a solid formed at the interface, which became more abundant over time.1H NMR analysis of the recovered solid indicated the formation of cage 32h in pure form. A MALDI-TOF experiment performed directly on the solid sample confirmed the attribution. This last result is particularly interesting since liquid-liquid interfaces represent another potentially useful field of action for self-assembly protocols, which has barely been explored so far [42]. 

Inorganic Rings and Polycyclic Cages Self-assembled Throngh Dative Bonds... 

Figure 26 An enormous chiral truncated tetrahedral cage self-assembles from 30 independent components. The naphthy-bridged 6w-pyrazolylpyridine ligand of this [Coi2Li8] + assembly is very slightly different in structure from a phenylene-bridged analog, which assembles a modest [Co4L6] tetrahedron...

Adamantane can be used to construct peptidic scaffolding and synthesis of artificial proteins. It has been introduced into different types of synthetic peptidic macrocycles, which are useful tools in peptide chemistry and stereochemistry studies and have many other applications as well. Introduction of amino acid-functionalized adamantane to the DNA nanostmctures might lead to construction of DNA-adamantane-amino acid nanostmctures with desirable stiffness and integrity. Diamondoids can be employed to constmct molecular rods, cages, and containers and also for utilization in different methods of self-assembly. In fact, through the development of self-assembly approaches and utilization of diamondoids in these processes, it would be possible to design and constmct novel nanostmctures for effective and specific carriers for each dmg. 

Crossley (89) described the self-assembly of a spherical cage-like structure made up of two zinc porphyrin dimers bound to a tetramine ligand. The 2 1 complex is stable at 10-6m concentrations, but addition of excess of ligand causes dissociation of the capsule with formation of a 1 1 complex. 

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. 

Construction of discrete and well-defined molecular architectures using organic ligands and metal ions through the self-assembly route has received much attention. A dinuclear Pd11 cage,636 includes a hexafluorophosphate ion inside the cavity. Self-assembly of a novel macrotricyclic cage... 

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

Fujita, M. Self-assembled macrocycles, cages and catenanes containing transition metals in their backbones. In Comprehensive Supramolecular Chemistry Sauvage, J.-P., Hosseini, M. W., Eds. Elsevier Oxford, 1996, Vol. 9, pp 253-282. 

Recent advances in nanotechnology have shown that self-assembled cage structures of nanometer dimensions can be used as constrained environments for the encapsulation of guest molecules with potential applications in drug delivery,... 

The encapsulation of classical and organometallic transition-metal complexes to yield molecules of the type complex in a complex is a very attractive research area. A variety of inclusion complexes of this type has been reported. Of relevance for this review are reports on the encapsulation of coordinatively unsaturated transition-metal complexes inside self-assembled coordination cages (120), cyclodextrins (121,122), and cucurbiturils (123). 

Recently, Bergman and Raymond reported on the stabilization of highly reactive organometallic species inside self-assembled [M4L6] coordination cages (120). The very reactive ion [CpRu(cis-l,3,7-octatriene)]BF4, for example, decomposes rapidly in aqueous solution (within minutes), but is stable for weeks in the same solvent when encapsulated in the tetrahedral [Ga4(L13)6]12- cage... 

The encapsulation of reactive organometallic complexes is not restricted to the anionic [Ga4(L13)6]12- cages. Thus, Fujita and coworkers were able to generate the coordinatively unsaturated complex [Cp Mn(CO)2] (Cp = C5H4Me) within a self-assembled [M Le] coordination cage 28 (Fig. 20) (132). Photoirradiation of solid 27 gave complex 28, the crystal structure of which confirms the presence of the unsaturated pyramidal [CpMn(CO)2] fragment. The direct observation of such intermediates is... 

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