Catenane definition

Our definitions of the stereoisomeric center, line, and plane all stipulate the existence of bonds between the ligating element and its ligands. The exclusive use of these elements limits our analysis to classical stereochemistry and thus does not encompass the so-called topological isomerism (47) of interlocked rings—catenanes (48)—or of knots. As there is no bond between the rings of the catenanes we cannot expect to handle such compounds with a system based on connectedness. At the present stage of development, this limitation in scope... 

We have seen how elegantly transition metals can template the formation of knots, but what about Nature s favourite templating interaction, the hydrogen bond A remarkably efficient molecular trefoil knot synthesis based on this interaction was reported by Vogtle and co-workers, who made a knotane in 20% yield [39]. This amazing route (Fig. 11) was uncovered serendipitously during the synthesis of catenanes. The crystal structure of the compound was the definitive proof for the structure, because neither NMR nor mass spectrometry could tell it apart conclusively from the macrocycles that are also formed. 

Chen et al. proved 30 separately binds both 5 and 14 in 1 1 and 1 2 stoichiometries <20060L211, 20060L1859>. Chen et al. used X-ray crystallography for definitive proof of their high-yielding synthesis of the [4]catenane of 32 with 3equiv of 15 (Figure 7). A catenane is a set of mechanically linked mactocycles. 

Anion-Directed Assembly, p. 51 Enzymes Characteristics and Mechanisms, p. 554 Hydrogen Bonding, p. 658 Molecular Squares, Boxes, and Cubes, p. 909 Molecular-Level Machines, p. 931 Protein Supramolecular Chemistry, p. 1161 Racks, Ladders, and Grids, p. 1186 Self-Assembling Catenanes, p. 1240 Self-Assembly Definition and Kinetic and TTjermot/ynam-ic Considerations, p. 1248 Self-Assembly in Biochemistiy, p. 1257 The Template Effect, p. 1493... 

Molecular Logic Gates, p. 893 Molecular Switches, p. 917 71 71 Interactions Theory and Scope, p. 1076 Rotaxanes and Pseudorotaxanes, p. 1194 Self-Assembling Capsules, p. 1231 Self-Assembling Catenanes, p. 1240 Self Assembly Definition and Kinetic and Thermodynamic Considerations, p. 1248 Supramolecular Polymers, p. 1443... 

In the chemical sense, one can immediately appreciate the potential and transversal applicability of these concepts, which have been reviewed authoritatively. There are numerous and varied chemical objects that are either slow to form or whose formation competes with that of other structures. Templates direct chemical structure formation, favoring the synthesis of a given product, and improving selectivity over other possible products. They can make feasible the preparation of chemical objects that would otherwise be impractical, such as catenanes and knots (see Self-Assembled Links Catenanes and Templated Synthesis of Knots and Ravels, Self-Processes). These considerations made Busch derive what has become a widely accepted definition a chemical template organizes an assembly of atoms, with respect to one or more geometric loci, in order to achieve a particular linking of atoms. ... 

Rare examples of unique topologies in such systems are known. However, it was recently realized that when the analysis includes cofactors and prosthetic groups such as seen in quinoproteins or iron-sulfur cluster proteins, interesting topologies including knots and catenanes are in fact more common than previously realized. As always, in considering stereochemical phenomena, our definition of connectivity is crucial. Earlier studies had counted only the amino acids as contributing to the connectivity of the system. When cofactors are included, more complex connectivities result. 

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