Self-assembled Cages

A variety of covalently-bound bicyclic molecules, capable of complexing and including smaller guest species, have been reported over many years.  

Lindoy, The Chemistry of Macrocyclic Ligand Complexes, Cambridge University Press, Cambridge, UK, 1989 G.W. Gokel, Crown Ethers and Cryptands, Royal Society of Chemistry, Cambridge, UK, 1991 R. Berscheid, I. Liier, C. Seel and F. Vogtle in Supramolecidar Chemistry, V. Balzani and L. De Cola, eds., Kluwer, Dordrecht, 1992, pp. 71-86. 

Phenyl groups orritted for clarity, MM2 minimised structure 

Based on the above study, larger pseudo-spherical host assemblies have been constructed from extended tetra-urea derivatives structures 29 and are 

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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,... 

Keywords Templates Hydrogen Bonding Self-assembly Cages Macrocycles Catenanes ... 

Another outstanding achievement in this domain was the synthesis of, of course unstable, [(CH3)2C(OH)PC2H5)3]+ cation 268 in the self-assembled cage 269 similar to 26 discussed in Section 2.1 [17]. 

Fiedler, D., Pagliero, D., Brumaghim, J.L., Bergman, R.G. and Raymond, K.N. (2004) Encapsulation of cationic ruthenium complexes into a chiral self-assembled cage. Inorg. Chem., 43 (3), 846-848. 

Kimura and co-workers have prepared a novel self-assembled cage composed of four trimeric Zn(II)-cyclen complexes joined with four tri-deprotonated trithiocyanuric acid molecules in aqueous solution. The 4 4 complex is thermo-... 

FIGURE 19 Top Molecular structure of Fujita s self-assembled cage, which is simply prepared by mixing an exo-triamine and encapped Pd(ll) ions in a 4 6 ratio (molar) (60). Bottom Side and top views of the CAChe-minimized structure of the ternary complex anthracene-maleimide C metallocage. (See Color Insert in the back of this book.)... 

Keywords Supramolecular chemistry. Self-assembly, Cage compounds. Metal complexes. Host-guest chemistry... 

T. Yamaguchi, M. Fujita, High selective photomediated 1,4-radical addition to o-quinones controlled by a self-assembled cage, Angew. Chem. Int. Ed., 2008, 47, 2067. 

M. Yoshizawa, T. Kusukawa, M. Kawano, T. Ohhara, I. Tanaka, K. Kurihara, N. Niimura, M. Fujita, Endohedral clusterization of ten water molecules into a molecular ice within the hydrophobic pocket of a self-assembled cage, J. Am. Chem. Soc., 2005, 127, 2798-2799. 

Fig. 3 Metallocapsules 6 and 7 and the x-ray structure of 7 [M=Co(II)]. Below Fujita s self-assembling cages 8 and 9.

Self-assembled cage structures have been established for tert-butyl alumoxanes of various degrees of association formed by hydrolysis of AlBuS [81], Thus, compounds such as BuSAU02(0H), Bu 7Al503(0H)2, Bu 8Al604(0H)2 [93], and Bu 6Al604(OH)4 have been structurally characterized [98]. 

One of the recent examples to underscore the unique water properties is the endohedral clusterization of water molecules into a molecular ice within a hydrophobic self-assembled cage. It was known earlier that the hydrogen-bond network of water can spontaneously grow not only on the surface of hydrophobic solute, affording stable hydrate... 

Figure 1 (a) X-ray crystal structure of self-assembled cage with oxygen atoms (water molecules) around the cage, (b) ORTEP... 

Yoshizawa M, Kumazawa K, Fujita M (2005) Room-temperature and solution-state observation of the mixed-valence cation radical dimer of tetrathiafulvalene, [(TTF)2]+, within a self-assembled cage. J Am Chem Soc 127 13456-13457. doi 10.1021/ja053508g... 

Electron transport through single molecules comprising aromatic stacks enclosed in self-assembled cages. Angew Chem Int Ed 50 5708-5711. doi 10.1002/anie.201100431... 

Kohyama Y, Murase T, Fujita M. A self-assembled cage as a non-covalent protective group regioselectivity control in the nuclet hihc substitution of aryl-substituted allylic chlorides. Chem Commun 2012 48 7811-3. 

Fiedler D, et al. Encapsulation of cationic ruthenium complexes into a chiral self-assembled cage. Inorg Chem 2004 43 846-8. 

Nishioka Y, Yamaguchi T, Yoshizawa M, Fujita M. Unusual [2-1-4] and [2+2] cycloadditions of arenes in the confined cavity of self-assembled cages. J Am Chem Soc 2007 129 7000-1. 

In solution and in gas phase, the characterization of self-assembled cages/ capsules requires analytical methods operating in timescales that are in accordance with their hfetimes (milliseconds to hours). NMR spectroscopy and mass spectrometry using soft methods (ESI, MALDI) for vaporization and ionization are appropriate. In some cases, the containers structures and their complexes have also been characterized in the solid state by X-ray diffiraction. Generally, the purification of supramolecular containers and their encapsulation complexes using chromatography is not feasible owing to dynamic features of the reversible self-assembly process that led to their formation. 

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