Supramolecular chemistry

Supramolecular chemistry refers to the area of chemistry which focuses on the noncovalent bonding interactions of molecules. Traditional organic synthesis involves the making and breaking of covalent bonds to construct a desired molecule. In contrast, supramolecular chemistry utilizes far weaker and reversible noncovalent interactions, such as hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi-pi interactions, and/or electrostatic effects to assemble molecules into multimolecular complexes. Important concepts that have been demonstrated by supramolecular chemistry include host-guest chemistry, self-assembly, and molecular recognition.

History

The importance of supramolecular chemistry was recognized by the 1987 Nobel Prize for Chemistry which was awarded to Donald J. Cram, Jean-Marie Lehn, Charles J. Pedersen in recognition of their work in this area. The development of selective "host-guest" complexes in particular, in which a host molecule recognizes and selectively binds a certain guest, was cited as an important contribution.

Origins

Research in this area has it origins in biological systems which are highly dependent on noncovalent interactions to function. For instance, the important breakthrough that allowed the elucidation of the double helical structure of DNA occurred when it was realized that there were two separate strands of nucleotides connected through hydrogen bonds. The use of noncovalent bonds is essential to replication because they allow the strands to be separated and used to template new double stranded DNA.

Application

Supramolecular chemistry and self-assembly processes in particular have been applied to the development of new materials. Large structures can be readily accessed using bottom-up synthesis as they are composed of small molecules requiring fewer steps to synthesize. Thus most of the bottom-up approaches to nanotechnology are based on supramolecular chemistry.

Supramolecular chemistry is often pursued to develop new functions that cannot appear from a single molecule. These functions include magnetic properties, light responsiveness, catalytic activity, self-healing polymers, chemical sensors, etc. Supramolecular research has been applied to develop high-tech sensors, processes to treat radioactive waste, compact information storage devices for computers, high-performance catalysts for industrial processes, and contrast agents for CAT scans.

Supramolecular chemistry is also important to the development of new pharmaceutical therapies by understanding the interactions at a drug binding site. In addition, supramolecular systems have been designed to disrupt protein-protein interactions that are important to cellular function.

Research in supramolecular chemistry also has application in green chemistry where reactions have been developed which proceed in the solid state directed by non-covalent bonding. Such procedures are highly desirable since they reduce the need for solvents during the production of chemicals.

Subdivisions

• Supermolecules
  • Host-guest chemistry
  • Molecular tectonics
  • Anion receptors
  • Helicates
  • Catenanes
  • Rotaxanes
  • Knotanes
• Supramolecular assemblies
  • Micelles
  • Membranes
  • Vesicles
  • Liquid crystals

See also

• Molecular complementarity
• Crystal engineering

References

• Lehn JM (1993). "Supramolecular chemistry". Science 260 (5115): 1762-3. PMID 8511582.