Naslov
Synthesis of [5]Rotaxanes Containing Bi- and Tridentate Coordination Sites in the Axis

Autori
Collin, Jean-Paul ; Durot, Stéphanie ; Keller, Michel ; Sauvage, Jean-Pierre ; Trolez, Yann ; Cetina, Mario ; Rissanen, Kari

Izvornik
Chemistry : a European journal (0947-6539) 17 (2011), 3; 947-957

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
click chemistry; copper; lithium; rotaxanes; zinc

Sažetak
A new example of a linear [5]rotaxane has been synthesized by using the traditional “gathering-andthreading” approach but based on an unusual axle incorporating a symmetrical bis(bidentate) chelating fragment built on a 4, 7-phenanthroline core. The stoppering reaction is particularly noteworthy since, instead of using a trivial bulky stopper as precursor to the blocking group, two semistoppered copper-complexed [2]pseudorotaxanes (namely [2]semirotaxanes) are used, which leads to the desired [5]rotaxane in good yield. The efficiency of the method relies on the use of “click” chemistry, with its very mild conditions, and on the protection by a transitionmetal (copper(I)) of the various coordinating groups present in the fragments to be interconnected (terpy and bidentate chelating groups), thus inhibiting potential detrimental side reactions during the copper-catalyzed stoppering reaction. Since the external fragments and the central core of the system contain tri- and bidentate chelating units, respectively, the axle of the final [5]rotaxane incorporates two types of coordinating units: two external terpy groups (terpy: 2, 2’:6’, 2’’-terpyridine) and two central bidentate ligands. Such a situation enables the system to tidy two different metals centers, and to localize them in a priori well-defined positions. This is what was observed when mixing the free ligand with a mixture of Zn^2+^ and Li^+^: the zinc(II) ions were unambiguously shown to occupy the external sites, whereas the Li^+^ cations were found in the central part of the [5]rotaxane. An X-ray diffraction study carried out on a [3]pseudorotaxane, the axis of which is similar to the central part of the [5]rotaxane axle, demonstrates that Zn^2+^ is clearly five-coordinate, the fifth ligand being a counterion, even when the coordination site of the pseudorotaxane is designed for four-coordinate metals, which is in marked contrast with copper(I) or Li^+^.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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