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Supramolecular assembly

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Title: Supramolecular assembly  
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Supramolecular assembly

An example of a supramolecular assembly reported by Atwood and coworkers in Science 2005, 309, 2037.
An example of a supramolecular assembly reported by Jean-Marie Lehn and coworkers in Angew. Chem., Int. Ed. Engl. 1996, 35, 1838-1840.

A supramolecular assembly or "supermolecule" is a well defined complex of molecules held together by noncovalent bonds. While a supramolecular assembly can be simply composed of two molecules (e.g., a DNA double helix or an inclusion compound), it is more often used to denote larger complexes of molecules that form sphere-, rod-, or sheet-like species. The dimensions of supramolecular assemblies can range from nanometers to micrometers. Thus they allow access to nanoscale objects using a bottom-up approach in far fewer steps than a single molecule of similar dimensions.

The process by which a supramolecular assembly forms is called liquid crystals and block copolymers.

Contents

  • Templating reactions 1
  • Hydrogen bond assisted supramolecular assembly 2
  • Applications 3
  • See also 4
  • References 5
  • Further reading 6

Templating reactions

18-crown-6 can be synthesized from using potassium ion as the template cation
Illustrations of a. metal-organic frameworks and b. supramolecular coordination complexes

As studied in coordination chemistry, metals (usually transition metals) exist in solution bound to ligands, In many cases, the coordination sphere defines geometries conducive to reactions either between ligands or involving ligands and other external reagents.

A well known metal-templating was described by Charles Pederson in his synthesis of various crown ethers using metal cations as template. For example, 18-crown-6 strongly coordinates potassium ion thus can be prepared through the Williamson ether synthesis using potassium ion as the template metal.

Metals are frequently used for assembly of large supramolecular structures. Metal organic frameworks (MOFs) are one example.[1] . MOFs are infinite structures where metal serve as nodes to connect organic ligands together. SCCs are discrete systems where selected metals and ligands undergo self-assembly to form finite supramolecular complexes,[2] usually the size and structure of the complex formed can be determined by the angularity of chosen metal-ligand bonds.

Hydrogen bond assisted supramolecular assembly

Hydrogen bonds in (a) DNA duplex formation and (b) protein β-sheet structure
(a) Representative hydrogen bond patterns in supramolecular assembly. (b) Hydrogen bond network in cyanuric acid-melamine crystals.

carboxylic acids, ureas, amines, and amides are commonly used to assemble higher order structures upon hydrogen bonding.

Hydrogen bond play an essential role in the assembly of secondary and tertiary structures of large biomolecules. DNA double helix is formed by hydrogen bonding between nucleobases: adenine and thymine forms two hydrogen bonds, while guanine and cytosine forms three hydrogen bonds (Figure "Hydrogen bonds in (a) DNA duplex formation"). Another prominent example of hydrogen bond-assisted assembly in nature is the formation of protein secondary structures. Both the α-helix and β-sheet are formed through hydrogen bonding between the amide hydrogen and the amide carbonyl oxygen (Figure "Hydrogen bonds in (b) protein β-sheet structure").

In supramolecular chemistry, hydrogen bonds have been broadly applied to crystal engineering, molecular recognition, and catalysis.[3][4] Hydrogen bonds are among the mostly used synthons in bottom-up approach to engineering molecular interactions in crystals. Representative hydrogen bond patterns for supramolecular assembly is shown in Figure "Representative hydrogen bond patterns in supramolecular assembly".[5] A 1: 1 mixture of cyanuric acid and melamine forms crystal with a highly dense hydrogen-bonding network. This supramolecular aggregates has been used as templates to engineering other crystal structures.[6]

Applications

Supramolecular assemblies have no specific applications but are the subject of many intriguing reactions. A supramolecular assembly of liquid crystaline lattices. Each cylindrical supramolecular assembly functions as an individual wire. High charge carrier mobilities for holes and electrons were obtained.

See also

References

  1. ^ Cook, T. R.; Zheng, Y.; Stang, P. J., Chem. Rev. 2013, 113, 734.
  2. ^ Paul, R. L.; Bell, Z. R.; Jeffery, J. C.; McCleverty, J. A.; Ward, M. D., Proc. Natl. Acad. Sci. 2002, 99, 4883.
  3. ^ Lehn, J. M., Science 1985, 227, 849.
  4. ^ Meeuwissen, J.; Reek, J. N. H., Nat. Chem. 2010, 2, 615.
  5. ^ Desiraju, G. R., J. Am. Chem. Soc. 2013, 135, 9952.
  6. ^ Seto, C. T.; Whitesides, G. M., J. Am. Chem. Soc. 1993, 115, 905.
  1. ^ Selective Differentiation of Neural Progenitor Cells by High-Epitope Density Nanofibers Gabriel A. Silva, Catherine Czeisler, Krista L. Niece, Elia Beniash, Daniel A. Harrington, John A. Kessler, Samuel I. Stupp Science Volume 303, Issue 5662, Pages 1352-1355 2004 Abstract
  2. ^ "Self-assembly of Amphiphilic Dendritic Dipeptides into Helical Pores" Virgil Percec, Andrés E. Dulcey, Vekatachalapathy S. K. Balagarusamy, Yoshiko Miura, Jan Smidrkal, Mihai Peterca, Sami Nummelin, Ulrica Edlund, Steven D. Hudson, Paul A. Heiney, Hu Duan, Sergei N. Magonov & Sergei A. Vinogradov Nature 2004, 430(7001), 764-768 Abstract
  3. ^ "Self-organization of Supramolecular Helical Dendrimers into Complex Electronic Materials" V. Percec, M. Glodde, T. K. Bera, I. Shiyanovskaya, K. D. Singer, V. S. K. Balagarusamy, P. A. Heiney, I. Schnell, A. Rapp, H.-W. Spiess, S. D. Hudson & H. Duan Nature 2002, 419(6905), 384-387.

Further reading

  • Dirk G Kurth. "Challenges and breakthroughs in recent research on self-assembly" Sci. Technol. Adv. Mater. 9 No 1(2008) 014109 (96 pages) [10]
  • Sareeya Bureekaew, Satoru Shimomura and Susumu Kitagawa. "Metallo-supramolecular modules as a paradigm for materials science" Sci. Technol. Adv. Mater. 9 No 1(2008) 014103 (25 pages) [11]
  • Katsuhiko Ariga, Jonathan P Hill, Michael V Lee, Ajayan Vinu, Richard Charvet and Somobrata Acharya. "Chemistry and application of flexible porous coordination polymers" Sci. Technol. Adv. Mater. 9 No 1(2008) 014108 (12 pages) [12]
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