Macrocycle

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A macrocycle is, as defined by IUPAC, "a cyclic macromolecule or a macromolecular cyclic portion of a molecule."[1] In the chemical literature, macrocycles varyingly include molecules containing rings of 8 or more atoms,[1][2] or 12 or more atoms.[2][page needed] In general, coordination chemists define a macrocycle more narrowly as a cyclic molecule with three or more potential donor atoms that can coordinate to a metal center. A well-known example is the group of drugs known as macrolides. The IUPAC definition notes that a "cyclic macromolecule has no end-groups but may nevertheless be regarded as a chain," and that "macrocycle is sometimes used [in the literature] for molecules of low relative molecular mass that are not considered 'macromolecules.[3]

Macrocycle effect[edit]

Crystal structure of a Zn(II) ion coordinated to cyclen and ethanol reported in Inorg. Chem., 1997, 4579-4584.

The macrocyclic effect was discovered in 1969.[3][non-primary source needed] Coordination chemists study macrocycles with three or more potential donor atoms in rings of greater than nine atoms, as these compounds often have strong and specific binding with metals.[4][page needed] This property of coordinating macrocyclic molecules is termed the macrocycle effect, and is a special example of the chelate effect.[citation needed] This so-called macrocyclic effect is thought to be a combination of the entropic effect seen in the chelate effect, together with an additional energetic contribution that comes from the preorganized nature of the ligating groups (that is, no additional strains are introduced to the ligand on coordination).[4]

Synthesis[edit]

In general, macrocycles are synthesized from smaller, usually linear, molecules.

Historical uses[edit]

Macrocycles have been in use for several decades as synthetic dyes. Phthalocyanine is a porphyrin analogue, which is arguably the most useful, in uses as dyes and pigments since their discovery in 1928, due to their dark-blue colour. However, there are many other uses for them. Their name comes from their synthetic precursor, phthalodinitrile.[5][page needed]

Biological macrocycles[edit]

Related molecular categories[edit]

  • Ligand: an atom, ion, or functional group that is bonded to one or more central atoms or ions.
  • Chelate: a multidentate ligand, containing more than one donor atom.
  • Cryptand: a macrocycle with multiple loops (e.g., bicyclic).
  • Rotaxane: macrocycle(s) stuck on a stick, generally freely
  • Catenane: interlocked molecular rings (like a chain).
  • Molecular knot: a molecule in the shape of a knot such as a trefoil knot.

References[edit]

  1. ^ Still, W. C.; Galynker, I. Tetrahedron 1981, 37, 3981-3996.
  2. ^ J. D. Dunitz. Perspectives in Structural Chemistry (Edited by J. D. Dunitz and J. A. Ibers), Vol. 2, pp. l-70; Wiley, New York (1968)
  3. ^ "Glossary of basic terms in polymer science (IUPAC Recommendations 1996)" (PDF). Pure and Applied Chemistry 68 (12): 2287–2311. 1996. doi:10.1351/pac199668122287. 
  4. ^ Weller, M. et al (2014), Inorganic Chemistry, 6th edition, Oxford University Press
  1. ^ Parker, S.P. (2002). McGraw-Hill Science & Technology Dictionary. McGraw-Hill. ISBN 978-0070423138. [page needed]
  2. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "macrocycle".
  3. ^ Milgrom, L.R (1997). The Colours of Life: An Introduction to the Chemistry of Porphyrins and Related Compounds. New York: Oxford University Press. ISBN 0-19-855380-3.  (hardbound) ISBN 0-19-855962-3 (pbk.)[page needed]
  4. ^ Cabbines, D. K.; Margerum, D. W. (1969). "Macrocyclic effect on stability of copper(II) tetramine complexes". J. Am. Chem. Soc. 91 (23): 6540–6541. doi:10.1021/ja01051a091. [non-primary source needed]
  5. ^ Melson, G.A., Ed. (1979). Coordination Chemistry of Macrocyclic Compounds. New York: Plenum Press. ISBN 0-306-40140-1. [page needed]
  6. ^ Jung, J.E.; Seung, S.Y. (2002). Bulletin of the Korean Chemical Society 23 (10): 1483–1486. doi:10.5012/bkcs.2002.23.10.1483.  Missing or empty |title= (help)[better source needed][non-primary source needed]

See also[edit]

Further reading[edit]