Interlocked molecules molecular topology

With precise design criteria established, supramolecular interactions have been exploited to design and synthesise new and functional mechanically interlocked molecules in high yields [9]. Over a relatively short period of time, mastery of controlled synthesis of mechanically interlocked molecules has led to an extraordinary array of functional materials and molecular machines [10]. Examples of these include logic gates, sensors for explosives, anions and cations, in addition to exquisite molecules with complex topologies (such as molecular knots) that have yet to be thoroughly exploited. 

Almost a century has elapsed between Willstatters visionary speculation about a molecule made of two interlocked rings - a catenane - and the todays outspreading molecular chemistry concerned with topology. 

Self-assembly is a particular powerful tool in synthesising up large scale nanostructures are topologically complex molecules such as molecular machines and topologically interlocked species. 

One of the focuses in CyD applications is their use as components of devices in systems with nontrivial topological properties, i.e. catenanes, rotaxanes [1-8], and polyrotaxanes [1, 9,10] presented in some detail in Chapter 12. For a recent review of interlocked assemblies see Ref [11]. This is a part of novel "bottom up approach to the construction of devices on the basis of one molecule or one molecular aggregate [12]. 

A natural extension of the work described in Sect. 2.4 was to prepare a Cu(l)-complexed [2]catenane with macrocycles incorporating the Zn and Au porphyrins. [2]catenanes are topologically non-trivial molecules (non-planar molecular graph) in which two rings are interlocked but not linked [23,24]. Therefore, differentiating the rings with Zn- and Au-porphyrins enables us to study photoinduced electron transfer in mechanical bond systems and also to have information on the conformation of the system. 

The effect of interlocking on the properties of molecules is dramatic. For example, the basicity of the 2,9-diphenyl-1.10-phenanthroline unit is enhanced by several orders of magnitude when it is present in a [2]catenand. The proton catenate displays a similar molecular structure to that of the corresponding copper(I) catenate, whereas that of the catenand is completely different. The special topology of the catenands and knots makes them unique ligands, with strong complexes being formed with a variety of metal ions. ° ... 

Perhaps the most challenging class of molecules to synthesize using classical organic chemistry is the intertwined species known as catenanes. Catenanes involve two or more cyclic molecular strands that are mechanically interlocked with each other. The resulting attachment is not chemical in nature, although it is created by the formation of chemical linkages. The cycles are instead considered to be "topologically" bound to each other. 

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