Transition metal-complexed catenane

COlfen H (2007) Bio-inspired Mineralization Using Hydrophilic Polymers. 271 1-77 Collin J-P, Heitz V, Sauvage J-P (2005) Transition-Metal-Complexed Catenanes and Rotax-anes in Motion Towards Molecular Machines. 262 29-62 Collins BE, Wright AT, Anslyn EV (2007) Combining Molecular Recognition, Optical Detection, and Chemometric Analysis. 277 181-218 Collyer SD, see Davis F (2005) 255 97-124 Commeyras A, see Pascal R (2005) 259 69-122 Coquerel G (2007) Preferential Crystallization. 269 1-51 Correia JDG, see Santos I (2005) 252 45-84 Costanzo G, see Saladino R (2005) 259 29-68 Cotarca L, see Zonta C (2007) 275 131-161 Credi A, see Balzani V (2005) 262 1-27 Crestini C, see Saladino R (2005) 259 29-68... 

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

Transition metal-complexed catenanes and rotaxanes as light-driven molecular machines prototypes 05CL742. 

Although the number of applications of olefin metathesis to transition metal complexes is small compared to the number of applications in organic synthesis, this field is becoming increasingly important. Spectacular examples are the double RCM reactions of copper phenanthroline complexes as a synthetic route to catenanes [113] or a recently reported approach to steric shielding of rhenium complex terminated sp-carbon chains [114]. 

The group of Sauvage et al. [121] produced various [2]catenanes by using transition metal complexes as templates. Figure 41 illustrates one of their... 

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. 

Wozniak and coworkers described recently the first heterodinuclear bismacrocyclic transition metal complex 34 + (Fig. 14.5) that exhibits potential-driven intramolecular motion of the interlocked crown ether unit.25 26 Although the system contains transition metals, the main interaction between the various subunits, which also allowed to construct catenane 34+, is an acceptor-donor interaction of the charge transfer type. 

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. 

Figure 24 (a) Schematic representation of a transition-metal-complexed [2]catenane containing two differ-... 

Figure 2.22. Strategies for the transition metal-templated synthesis of catenanes. The metal (in) predisposes two fragments as open chelates (A) (strategy I) or as a macrocyclic chelate (E) and an open chelate (strategy II) in intermediates (B) and (F), respectively. Cyclization of these intermediate complexes with the chain fragments (C) provides the [2]-catenate complex (D).

Copper complexes are known in oxidation states ranging from 0 to +4, although the +2 (cupric) and the +1 (cuprous) oxidation states are by far the most common, with the divalent state predominating. Only a relatively small number of Cu complexes have been characterized and the Cu° and oxidation states are extremely rare. A few mixed valence (see Mixed Valence Compounds) polynuclear species have also been isolated examples include a CuVCu species and a Cu /Cu catenane. The coordination numbers and geometries (see Coordination Numbers Geometries) of copper complexes vary with oxidation state. Thus, the majority of the characterized Cu complexes are square planar and diamagnetic, as is common for late transition metals with d electronic configurations. 

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