Interlocked molecules applications

Interlocked molecules such as rotaxanes initially gained interest due to their interesting topology and associated synthetic challenge, but recent efforts have showed that they can be used in many important applications that will be discussed in this chapter (Scheme 6.1). 

One of the potential applications of mechanically interlocked molecules is construction of molecular-scale devices such as molecular machines and switches. [2J(Pseudo)rotaxanes containing CB 6] were studied along... 

Recently, a polyrotaxane network material has been practically used, for the first time, as a coating material for mobile phones in Japan. This is an epoch-making event in the science and technology of interlocked molecules, macromolecules, and related materials. Polymers possessing interlocked structures as key skeletons are, therefore, the most promising and intriguing materials, especially in the application fields. Polyrotaxanes and polycatenanes are characterized by the specific feamres based on the unique mobility of the noncovalently bonded components in their... 

This chapter has dealt with subjects concerned with synthesis and application of interlocked polymers. Marked progress in this area is evident in some aspects. In spite of the huge and wide progress in the chemistry of interlocked molecules such as rotaxane and catenane, the progress of the chemistry of the interlocked polymers has still... 

Mechanically interlocked molecules (MIMs), such as catenanes and rotaxanes, are molecules with at least two components that are not covalently bound, but interlocked in such a manner that they cannot be separated without the breaking of a covalent bond. Since this physical linkage is known as a mechanical bond [24], we refer to the stereochemistry of MIMs as mechanostereochemistry [25]. MIMs have been appreciated for their synthetic challenge and aesthetic value [26] as well as their potential applications. In particular, MIMs have garnered much interest as artificial molecular switches and machines [27-31] because their internal noncovalent bonding interactions can be modulated by external stimuli to control the relative translational and/or circumrotational motions of their interlocked... 

Owing to the popularity and vast modularity of the copper(l)-catalyzed azide-alkyne cycloaddition (CuAAC) [4,5], so-called click chemistry [24] (Fig. 1), many more 1,2,3-triazole-based anion receptors have been reported during the past 3 years (2008-2011). Reviews [25, 26] have been published to cover this new moiety in anion receptor chemistry. Therefore, this chapter will focus on triazole-based anion receptors that have not been reviewed to date. In addition, applications including sensors, ion-selective electrodes, catalysis, anion transport, and anion regulation, as well as their use in interlocked molecules, will be discussed. 

The ability of 1,2,3-triazole to bind anions with a C-H hydrogen bond is covered in Chap. 3, Binding Anions in Rigid and Reconfigurable Triazole Receptors by Lee and Hood. Applications including sensors, ion-selective electrodes, catalysis, anion transport and anion regulation, as well as their use in interlocked molecules, are discussed. 

In particular, rotaxane dendrimers capable of reversible binding of ring and rod components, such as Type II, pseudorotaxane-terminated dendrimers, can be reversibly controlled by external stimuli, such as the solvent composition, temperature, and pH, to change their structure and properties. This has profound implications in diverse applications, for instance in the controlled drug release. A trapped guest molecule within a closed dendrimeric host system can be unleashed in a controlled manner by manipulating these external factors. In the type III-B rotaxane dendrimers, external stimuli can result in perturbations of the interlocked mechanical bonds. This behavior can be gainfully exploited to construct controlled molecular machines. 

After numerous answers were brought to the synthetic challenge itself, there arose ever more insistently the quest for functions and properties of such special compounds. Already, even if still far from real applications, one can imagine, based on interlocked, threaded or knotted multi-component molecules, new organic materials, specific polymers, molecular devices or machines able to process and transfer energy, electrons or information. 

Mechanically interlocked molecular compounds, including catenanes, rotax-anes, and carceplex, are constituted of molecules composed of two or more components that cannot be separated from each other [95-98]. The development of strategy for achieving controlled self-assembling systems by non-covalent interaction enables one to prepare such attractive compounds for applications in nanoscale molecular devices. The dithiafulvene derivatives are effective electron donors, which are good candidates to form those supramolecular systems with appropriate acceptors by virtue of intermolec-ular CT interactions. In this chapter, dithiafulvene polymers forming rotax-ane structures are especially described. 

The application of this template to the clipping of acyclic dumbbell-shaped molecules to form rotaxanes [14] has received less intensive scrutiny but involves a similar synthetic scheme and conditions. A few representative examples of [2]rot-axanes synthesized in this manner (16-20) are shown in Figure 10.2 [15c, 18-21]. The use of a 1,5-dihydroxynaphthalene core in these cases usually results in higher yields of the desired interlocked products [18,21]. 

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]. 

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