Copper -complexed rotaxane

ELECTROCHEMICALLY DRIVEN MACHINES BASED ON PIROUETTING COPPER-COMPLEXED ROTAXANES... 

In this chapter, we would like to describe rotaxanes in which a new motion, pirouetting of the wheel around its axle, can be electrochemically triggered. The first distable copper-complexed rotaxanes 4(4)+ and 4(5)2 + synthesized in our group are represented in Fig. 14.7. The wheel of the rotaxane is a bis-coordinating macrocycle... 

Fig. 10. Principle of the electrochemically induced molecular motions in a copper complex rotaxane. The stable 4-coordinate monovalent complex [top left, the black circle represents Cu(I)] is oxidized to an intermediate tetrahedral divalent species [top right, the white circle represents Cu(II)]. This compound undergoes a complete reorganization process to afford the stable 5-coordinate Cu(II) complex [bottom right]. Upon reduction, the 5-coordinate monovalent state is formed as a transient [bottom left]. Finally, the latter undergoes the conformational change which regenerates the starting complex...

Fig. 13. Electrochemically triggered rearrangement of a [2]catenate containing two different rings. The principle is the same as the one described for the copper complex rotaxane (Fig. 10)...

Fig. 13 Principle of the electrochemically induced molecular motion in a rotaxane copper complex. The stable, four-coordinate monovalent complex is oxidized to an intermediate tetrahedral divalent species. This compound undergoes a rearrangement to afford the stable, five-coordinate copper(u) complex.

Copper(I)- free [2]rotaxane 12" (PF6 ) was obtained by treatment of 9 " (PF6 )2 with excess KCN (Fig. 6). The fact that demetalation of Cu" -complexed rotaxane 9 " afforded a single product 12 and the absence of release of the bis-porphyrin by macrocycle 3 is proof that the compound synthesized is a true rotaxane. Linking is provided only by steric crowding of the porphyrin moieties, preventing unthreading of the bis-porphyrin from macrocycle 3. 

The systems studied by Schuster and Guldi are reported in Fig. 22 56 and 57" are analogous to rotaxanes 33 and 40 with two zinc(II) porphyrins as stoppers, a Cu(I)(dpp)2 as the spacer and a C6o as the electron acceptor are appended to the macrocycle or included in it. SS is a catenane derived from 56 upon axial binding by a bidentate ligand to the zinc ions of the porphyrin stoppers. Rotaxanes 59" and 60 differ from 56 and 57" in having two 50 electron acceptors as stoppers and a zinc porphyrin electron donor appended to the macrocycle and differ from each other in the distance between the electron donor and the copper complex, which has been increased by insertion of a phenylamido group. 

Durola, F. and Sauvage, J. Fast electrochemically indnced translation of the ring in a copper-complexed [2]rotaxane The biisoquinoline effect. Angew. Chem. Int. Ed. 46, 3537-3540, 2007. 

Diederich, F., Dietrich-Buchecker, C., Nierengarten, J.-F. and Sauvage, J.-P. A copper(I)-complexed rotaxane with two fullerene stoppers. J. Chem. Soc., Chem. Commun. 7, 781-782, 1995. 

In order to make the copper central core as easy as possible to rotate, we thought that the bulky stoppers should be located far away from the central complex. We thus prepared and studied a new bistable rotaxane, depicted in Fig. 14.10, whose stoppers are indeed very remote from the copper center.31 This new dynamic system can indeed be set in motion more rapidly than the previously described systems. 

Fig. 8 Schematic representation of the electron transfer events occurring in copper(i)-complexed and template-free [2]-rotaxanes 2 and 3 (same conventions as in Figure 7).

Figure 2.28. Copper(I)-templated synthesis of [2]-rotaxane 81 from the thread 77, macrocycle 58, and Ru(II)-complex precursor 79.

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