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On the molecular level, the interlocked molecules cannot be separated without the breaking of the covalent bonds that comprise the conjoined molecules; this is referred to as a mechanical bond. Examples of mechanically interlocked molecular architectures include catenanes, rotaxanes, molecular knots, and molecular Borromean rings.
In order to access the molecular Borromean ring consisting of three unequal cycles a step-by-step synthesis was proposed by Jay S. Siegel and coworkers. [47] In physics, a quantum-mechanical analog of Borromean rings is called a halo state or an Efimov state, and consists of three bound particles that are not pairwise bound.
Further examples of supramolecular assemblies demonstrate that a variety of different shapes and sizes can be obtained using molecular self-assembly. [10] Molecular self-assembly allows the construction of challenging molecular topologies. One example is Borromean rings, interlocking rings wherein removal of one ring unlocks each of the other ...
The ring-system consists of three such interlocked rings. Reduction with sodium borohydride in ethanol affords the neutral Borromeand. [2] With the zinc removed, the three macrocycles are no longer chemically bonded but remain "mechanically entangled in such a way that that if only one of the rings is removed the other two can part company."
The interlocked rings rotate with respect to one another. This motion can often be evaluated 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 (recognition sites).
If the rings of the polycatenane are all of the same type, it can be defined as a homocatenane while if the subunits are different it is defined as heterocatenane. As a chain, the degree of motion of these structures is very high, greater than the one of a usual polymer, because the rings possess a reciprocal rotational, elongational and ...
A heterocycle or heterocyclic ring is a ring containing atoms of at least two different elements, i.e. a non-homocyclic ring. [2] A carbocycle or carbocyclic ring is a homocyclic ring in which all of the atoms are carbon. [3] An important class of carbocycles are alicyclic rings, [4] and an important subclass of these are cycloalkanes.
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). [1] Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of organic heterocycles .