Multiring Catenanes with a Macrobicyclic Core

Abstract

may be an indication that the "two-state model", on which the elucidation of the thermodynamic data is based, is most likely an oversimplification in this case. It seems reasonable that the reduction of the enthalpy term in the hybrid duplexes is due to a partly "incorrect" pairing geometry or to strain within the bicyclic strand. The reduction of the entropy term can be attributed to the reduced degree of rotational freedom in the sugar-phosphate backbone of the DNA analogues, although other contributions, especially from differences in duplex and single strand solvation, may also play an important role.

New Self-Assembled Structural Motifs in Coordination Chemistry

“…Figure illustrates the formation of a [2]catenate by this means;194a similar strategies have also been used in the syntheses of a series of [2]−[7]catenates. 194a, As the rings in such complexes involve purely covalent linkages, they have a cyclic primary structure which generates the catenane motif as a secondary structure. Multiringed catenates involving a tricyclic core have been prepared by analogous means, as have several catenates containing porphyrin moieties. −

75 Catenates formed by post-modification of a self-assembled precursor. The cyclization is shown of a self-assembled pseudorotaxane using a polyether diiodide.

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Spontaneous assembly of ten components into two interlocked, identical coordination cages

“…The framework of each cage is assembled from ®ve components: two tridentate ligands held together with three metal ions. Because each cage framework can bind an aromatic ring, two cage units will bind one another during their assembly process through the formation of a quadruple aromatic stack, giving rise to the ten-component interlocked supermolecule 16,17 .…”

[2]Catenane Synthesis via Covalent Templating

“…In addition, the overall chemical shift of the aliphatic proton signals is significantly reduced. This points to increased shielding and is common for methylene chains entrapped within macrocycles bearing aromatic rings [33, 36, 37] . However, the most striking difference is the downfield shift of 0.56 and 0.11 ppm, respectively, of the template aromatic ( c ) and methyl ester ( g ) protons.…”

“…This points to increased shielding and is commonf or methylene chains entrappedw ithin macrocycles bearinga romatic rings. [33,36,37] However, the mosts triking differencei st he downfield shift of 0.56 and 0.11ppm, respectively,o ft he template aromatic (c) and methyl ester (g)p rotons. As was observed for precatenane 9a and trivial bicycle 27 a,t his is probablyd ue to the rigid conformation of the interlocked rings in [2]catenane 10 b preventingt he macrocyclesf rom collapsing.…”