Interlocked molecules properties

This brief summary on template effects for the syntheses of interlocked molecules not only shows that a broad variety of different non-covalent interactions mediate the threading step in their preparations, it also intends to demonstrate how many different structural types of such molecules exist, each of which has its own properties and special characteristics. However, regardless of the different structures and varying features of these molecules, the common motif among all of them is the presence of a mechanical bond. 

During the past 20 years, mechanically interlocked molecules, known as catenanes and rotaxanes, many of them redox-active, have become readily accessible using template-directed protocols that rely upon the precepts of molecular recognition and self-assembly and the tenets of supramolecular assistance to covalent synthesis. By incorporating different recognition units with dissimilar redox properties into appropriate components, these compounds can often be induced to switch hysteretically between ground and metastable co-con-... 

Recently, much attention has been focused on the design and synthesis of intrerlocked molecules, such as rotaxanes and catenanes, because of their unique structures and properties.Host-guest interactions are used for the efficient preparation of such interlocked molecules. Previously, we found and reported that... 

A second class of highly appealing molecular architectures is molecular capsules." Their ability to encapsulate small organic molecules with a consequent alteration of the physical properties and chemical reactivity of the guests has made the synthesis and study of these structures a flourishing research field, as can be evidenced by the examples provided elsewhere. From a synthetic point of view, molecular capsules suffer the same problem as mechanically interlocked molecules. Capsules are typically formed through... 

In contrast, chloride complexation to the macrocycle isophthalamide cleft had no apparent effect on the system s dynamics, presumably due to the absence of any potential axle-anion interactions to lock the rotaxane co-conformation. Overall, the work shows that effective traceless ion pair temptation can prodnce uncharged mechanically interlocked molecules with ion-dependent switchable dynamic properties. 

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. 

In this contribution, we would like to show how such an approach allowed us to synthesize both soft and very hard molecule-based magnets. This contribution is organized as follows first, we define briefly the field of molecular magnetism, then we indicate the successive steps which led us to three-dimensional molecule-based magnets with fully interlocked structures. We describe these original structures in detail. Finally, we focus on the physical properties of these objects, with special emphasis on the huge coercivity of one of the compounds, which confers a memory effect on this compound. 

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. 

Because of their extraordinary dynamic properties, interlocked architectures [36-38] are particularly well suited for the development of molecular machinery [9]. Catenanes (from the Latin catena = chain) are molecules in which two or more macrocycles are interlocked. Rotaxanes (from the Latin rota = wheel and axis = axle) are molecular species in which one or more macrocycles are threaded onto a linear component and de-threading is prevented by bulky stoppers (Fig. 4). 

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