Rotaxanes molecular machines

The properties of these rotaxane dendrimers are quite different from those of the individual rotaxanes or dendrimers and often a blend of both. In view of the versatile characteristics that a dendron or dendrimer can manifest, several new properties can be imparted to the rotaxanes. For example, the solubility of rotaxanes in organic solvents as well as in water can be significantly improved when large dendrimer units are appended enhancing the prospects of their use as molecular machines. The dendritic units can also influence the photo/electro-chemical properties of the rotaxanes. Employing photo-receptive dendron units, photo chemically driven molecular machines may be developed, where the dendrons act as antenna for photo-harvesting [62]. 

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. 

J.-P. Sauvage, Transition Metal-Containing Rotaxanes and Catenanes in Motion Toward Molecular Machines and Motors , Acc Chem. Res. 1998,31, 611-619. 

Keywords Molecular Devices a Molecular Machines a Molecular Wires a Antenna Systems a Molecular Switches a Plug/socket Systems a Pseudorotaxanes a Rotaxanes a Catenanes a Supramolecuiar Chemistry a Photochemistry a Electrochemistry a Luminescence... 

Besides their topology, rotaxanes and catenanes are also appealing systems for the construction of molecular machines because (i) the mechanical bond allows a large variety of mutual arrangements of the molecular components, while conferring stability to the system, (ii) the interlocked architecture limits the amplitude of the intercomponent motion in the three directions, (iii) the stability of a specific... 

Electrochemically Driven Molecular Machines Based on Transition-metal Complexed Catenanes and Rotaxanes... 

Tetrathiafulvalene and its derivatives are electroactive and can be easily and reversibly oxidized to TTF + and TTF2 +. The TTF skeleton now occupies a critical position as far as switchable properties are concerned, and behaves as a key unit for a number of supramolecular concepts. For instance, the recent years have seen an increasing contribution of TTF to the preparation of interlocked compounds such as rotaxanes and catenanes. These systems are of particular importance as candidates for molecular machines. 

Dietrich-Buchecker, C., Jimenez-Molero, M.C., Sartor, V., and Sauvage, J.-P. (2003) Rotaxanes and catenanes as prototypes of molecular machines and motors, PureAppl. Chem. 75, 1383-1393. 

Balzani, V., Venturi, M., Credi, A. Molecular Devices and Machines. A Jorney into the Nanoworld, Wiley-VCH, Weinheim, 2003 b) Feringa, B.L. (ed.), Molecular Switches, Wiley-VCH, Weinheim, 2001 c) Raehm, L., Sauvage, J.-P. Molecular machines and motors based on transition metal-containing catenanes and rotaxanes, Struct. Bond. 99 (2001), 55-78. 

A review on molecular machines useful for the design of chemosensors emphasizing, among others, modified CDs as molecular sensors, and on rotaxanes and catenanes is published [36],... 

Metallo-Rotaxanes and Catenanes as Redox Switches Towards Molecular Machines and Motors... 

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