Rotaxanes Containing Transition Metals

Rotaxanes Containing Transition Metals From Electronic to Molecular Motion... 

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

In this chapter, we will focus on transition metal-based catenanes and rotaxanes. We will restrict ourselves to compounds that are set in motion by an electrochemical signal. Indeed, the electrochemical techniques represent privileged methods for piloting these machines since they contain electroactive transition metal centers or complexes. In addition to triggering the motions, electrochemistry allows to investigate the dynamic properties of the compounds. 

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. 

Apart form a great number of chiral NHC carbenes that have been used as ligands in enantioselective transition-metal catalysis (Gade and Bellemin-Laponnanz 2007), some less usual heterazolium salts have been tested in organocatalytic transformations. A planar-chiral thia-zolium salt (Pesch et al. 2004) and a rotaxane-derived precatalyst were reported (Tachibana et al. 2004), as well as catalytically active peptides containing an unnatural thiazolium-substituted alanine amino acid (Fig. 3 Mennen et al. 2005a,b). 

Another area of NEMS that is receiving tremendous attention is the mimicry of biological systems, aptly referred to as biomimetics. For instance, in the development of linear molecular muscles that undergo contraction and extension movements. Initial work in this field utilized transition metal complexes containing rotaxanes and catenanes, due to the nondestructive redox processes occurring on the metal centers.Though these complexes were actuated by a chemical reaction, the movement was in a noncoherent manner. In order to better mimic skeletal muscle movement, one has to look at the mode of motion within the most efficient molecular machines - in our human bodies. 

Higher order [n]-rotaxanes could be, in principle, synthesized by the transition metal-controlled threading process, provided that the linear component contains the... 

Figure 51 Principle of transition metal-templated synthesis of a [3]-rotaxane, from two chelating macrocycles (B) and a bis-chelate-containing molecular thread (A) functionalized with reactive end groups X (same conventions as in Figure 43). (ii) Threading step, affording prerotaxane (C) construction of the porphyrin stoppers providing copper(I)-complexed [3]-rotaxane (D).

Molecular Machines and Motors Based on Transition Metal-Containing Catenanes and Rotaxanes... 

Molecular Motions in Transition Metal-Containing Rotaxanes. . 58... 

Raehm L (2001) Molecular Machines and Motors Based on Transition Metal-Containing Catenanes and Rotaxanes 99 55-78 Rakke T, see Kjekshus A (1974) 19 45-83 Rakke T, see Kjekshus A (1974) 19 85-104... 

Sauvage. J.-P. Transition metal-containing rotaxanes and catenanes in motion Toward molecular machines and motors. Acc. Chem. Res. 1998, 31. 611-619. 

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