Inclusion compound

Example of an inclusion complex consisting of a p-xylylenediammonium bound within a cucurbituril[1]

In host-guest chemistry, an inclusion compound is a complex in which one chemical compound (the "host") has a cavity into which "guest" compound can be accommodated.[2] The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which guest molecules can fit. If the guest is enclosed on all sides so that it is ‘trapped’, the compound is known as a clathrate. In molecular encapsulation, a guest molecule is trapped inside another molecule.

Examples and case studies

Calixarenes

Calixarenes and related formaldehyde-arene condensates are one class of hosts that form inclusion compounds. One famous illustration is the adduct with cyclobutadiene, which otherwise is unstable.[3]

Cyclodextrins

Cyclodextrins are well established hosts for the formation of inclusion compounds.Guest molecules include ferrocene. When a solution of both compounds in a 2:1 ratio in water is under hydrothermal conditions at 100 degree C for 2 days and then allowed to rest for 10 hours at room temperature orange-yellow crystals form. X-ray diffraction analysis of these crystals reveals a 4:5 inclusion complex with 4 molecules of ferrocene included in the cavity of 4 cyclodextrine molecules and with the fifth ferrocene molecule sandwiched between two stacks of ferrocene – cyclodextrine dimers.

Cyclodextrin also forms inclusion compounds with fragrance molecules. As a result, the fragrance molecules have a reduced vapor pressure and are more stable towards exposure to light and air. When incorporated into textiles the fragrance lasts much longer due to the slow-release action.

Cryptands

Cryptands are analogs to crown ethers useful as carriers in what become lipophilic complexes that convey their guest cation in suchwise that the ligand binds the substrates 'within' their binding ("interned" alongside)

References

  1. ↑ Freeman, Wade A. (1984). "Structures of the p-xylylenediammonium chloride and calcium hydrogensulfate adducts of the cavitand 'cucurbituril', C36H36N24O12". Acta Crystallogr B: 382–387. doi:10.1107/S0108768184002354.
  2. ↑ Lisnyak, Yuriy V.; Martynov, Arthur V.; Baumer, Vyacheslav N.; Shishkin, Oleg V.; Gubskaya, Anna V. (2007-08-01). "Crystal and molecular structure of β-cyclodextrin inclusion complex with succinic acid". Journal of Inclusion Phenomena and Macrocyclic Chemistry. 58 (3–4): 367–375. doi:10.1007/s10847-006-9284-x. ISSN 0923-0750.
  3. ↑ "The Taming of Cyclobutadiene Donald J. Cram, Martin E. Tanner, Robert Thomas". Angewandte Chemie International Edition in English. 30: 1024–1027. 1991. doi:10.1002/anie.199110241.
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  • ^ Pharmacokinetic delivery and metabolizing rate of nicardipine incorporated in hydrophilic and hydrophobic cyclodextrins using two-compartment mathematical model S. Shityakov and C. Förster ScientificWorldJournal, 2013, 131358 Abstract
  • ^ Ionization states, cellular toxicity and molecular modeling studies of midazolam complexed with trimethyl-beta-cyclodextrin S. Shityakov, T. Sohajda, I. Puskás, N. Roewer, C. Förster C and J. A. Broscheit Molecules, 2014, (10), 16861–16876 Abstract
  • ^ A unique tetramer of 4:5 -cyclodextrin–ferrocene in the solid state Yu Liu, Rui-Qin Zhong, Heng-Yi Zhang and Hai-Bin Song Chemical Communications, 2005, (17), 2211–2213 Abstract
  • ^ Fragrance-release Property of β-Cyclodextrin Inclusion Compounds and their Application in Aromatherapy C. X. Wang, Sh. L. Chen Journal of Industrial Textiles, Vol. 34, No. 3, 157–166 (2005) Abstract
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