Catenane


Catenane

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A catenane is a mechanically-interlocked molecular architecture consisting of two or more interlocked macrocycles. The interlocked rings cannot be separated without breaking the covalent bonds of the macrocycles. Catenane is derived from the Latin "catena" meaning "chain". They are conceptually related to other mechanically-interlocked molecular architectures, such as rotaxanes, molecular knots or molecular Borromean rings. Recently the terminology "mechanical bond" has been coined that describes the connection between the macrocycles of a catenane.

ynthesis

There are two primary approaches to the organic synthesis of catenanes. The first is to simply perform a ring-closing reaction with the hope that some of the rings will form around other rings giving the desired catenane product. This so-called "statistical approach" led to the first successful synthesis of a catenane; however, the method is highly inefficient, requiring high dilution of the "closing" ring and a large excess of the pre-formed ring, and is rarely used.

The second approach relies on supramolecular preorganization of the macrocyclic precursors utilizing hydrogen bonding, metal coordination, hydrophobic forces, or coulombic interactions. These non-covalent interactions offset some of the entropic cost of association and help position the components to form the desired catenane upon the final ring-closing. This "template-directed" approach, together with the use of high-pressure conditions, can provide yields of over 90%, thus improving the potential of catenanes for applications. An example of this approach used bis-bipyridinium salts which form strong complexes threaded through crown ether bis(para-phenylene)-34-crown-10.

Properties and applications

A particularly interesting property of many catenanes is the ability of the rings to rotate through each other. This motion can often be detected and measured by NMR spectroscopy, among other methods. When molecular recognition motifs exist in the finished catenane (usually those that were used to synthesize the catenane), the catenane can have one or more thermodynamically preferred positions of the rings with respect to each other. In the case where one recognition site is a switchable moiety, a mechanical molecular switch results. When a catenane is synthesized by coordination of the macrocycles around a metal ion, then removal and re-insertion of the metal ion can switch the free motion of the rings on and off.

Catenanes have been synthesized incorporating many functional units, including redox-active groups (e.g. viologen, TTF), photoisomerizable groups (e.g. azobenzene), fluorescent groups and chiral groups. Some such units have been used to create molecular switches as described above, as well as for the fabrication of molecular electronic devices and molecular sensors.

Families of catenanes

There are a number of distinct methods of holding the precursors together prior to the ultimate ring-closing reaction in a template-directed catenane synthesis. Each noncovalent approach to catenane formation results in what can be considered different families of catenanes.

Another family of catenanes are called pretzelanes or bridged [2] catenanes after their likeness to pretzels with a spacer linking the two macrocycles. In one such system Ref|1 one macrocycle is an electron deficient oligo Bis-bipyridinium ring and the other cycle is crown ether cyclophane based on paraphenylene or naphthalene. X-ray diffraction shows that due to pi-pi interactions the aromatic group of the cyclophane is held firmly inside the pyridinium ring. A limited number of (rapidly-interchanging) conformers exist for this type of compound.

In handcuff-shaped catenanes Ref|1, two connected rings are threaded through the same ring. The bis-macrocycle (red) contains two phenanthroline units in a crown ether chain. The interlocking ring is self-assembled when two more phenanthroline units with alkene arms coordinate through a copper(I) complex followed by a metathesis ring closing step.

Nomenclature

In catenane nomenclature, a number in square brackets precedes the word "catenane" in order to indicate how many rings are involved.Ref|3 Discrete catenanes up to a [7] catenane have been synthesized and isolated.

ee also

*Olympiadane

References

# "Dynamic Chirality in Donor-Acceptor Pretzelanes" Y. Liu, S. A. Vignon, X. Zhang, P. A. Bonvallet, S. I. Khan, K. N. Houk, and J. F. Stoddart J. Org. Chem.; 2005; 70(23) pp 9334 - 9344; (Article) DOI: 10.1021/jo051430g [http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/jo051430g Graphical Abstract] [http://pubs.acs.org/subscribe/journals/joceah/suppinfo/jo051430g/jo051430gsi20050718_075148.pdf detailed molecular structure]
# "A catenane consisting of a large ring threaded through both cyclic units of a handcuff-like compound" Julien Frey, Tomá Kraus, Valérie Heitz and Jean-Pierre Sauvage Chemical Communications, 2005, (42), 5310 - 5312 [http://www.rsc.org/Publishing/Journals/CC/article.asp?doi=b509745b Abstract] [http://www.rsc.org/suppdata/CC/b5/b509745b/b509745b.pdf detailed molecular structure]
# "Nomenclature for Catenanes, Rotaxanes, Molecular Knots, and Assemblies Derived from These Structural Elements." O. Safarowsky, B. Windisch, A. Mohry, F. Vögtle. Journal für praktische Chemie, 342:5, 437-444, 2000. doi|10.1002/1521-3897(200006)342:5<437::AID-PRAC437>3.0.CO;2-7


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Look at other dictionaries:

  • Catenane — Caténane Un caténane. Un caténane est une architecture moléculaire formée d au moins deux macrocycles imbriqués l un dans l autre, formant une sorte de chaine (en latin catena). Deux cycles imbriqués ne peuvent pas être séparés sans casser au… …   Wikipédia en Français

  • caténane — [ katenan ] n. f. • 1976; angl. catenane (1960); du lat. catena « chaîne » ♦ Biochim. Groupe de molécules constituées d anneaux entrelacés comme ceux d une chaîne …   Encyclopédie Universelle

  • Catenane —   Plural, Catenaverbindungen, chemische Verbindungen, bei denen zwei oder mehrere Einzelringe wie die Glieder einer Kette ineinander greifen. Catenane haben v. a. in der präparativen organischen Chemie Bedeutung …   Universal-Lexikon

  • Caténane — Un caténane. Un caténane est une architecture moléculaire formée d au moins deux macrocycles imbriqués l un dans l autre, formant une sorte de chaine (en latin catena). Deux cycles imbriqués ne peuvent pas être séparés sans casser au moins une… …   Wikipédia en Français

  • Catenane — Stäbchenmodell eines Catenans (Stoddart et al., Chem. Commun., 1991, 634 639) …   Deutsch Wikipedia

  • catenane — katenanas statusas T sritis chemija apibrėžtis Junginys, sudarytas iš vienas per kitą pervertų cheminiu ryšiu nesusijungusių žiedų. atitikmenys: angl. catenane rus. катенан …   Chemijos terminų aiškinamasis žodynas

  • catenane — /kat n ayn /, n. any of the class of chemical compounds containing two or more rings that are interlocked without being bonded chemically. [CATEN(A) + ANE] * * * …   Universalium

  • catenane — noun Any compound, especially a hydrocarbon, having two or more rings interconnected like the links of a chain, without a covalent bond …   Wiktionary

  • Catenane — Ca|te|na|ne, Ca|te|na|ver|bin|dun|gen die (Plur.) <zu lat. catena »Kette«> chemische Verbindungen, bei denen zwei od. mehrere Einzelringe wie Glieder einer Kette ineinander greifen …   Das große Fremdwörterbuch

  • catenane — /kat n ayn /, n. any of the class of chemical compounds containing two or more rings that are interlocked without being bonded chemically. [CATEN(A) + ANE] * * * catˈenane noun (chem) A compound having molecules linked like a chain • • • Main… …   Useful english dictionary


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