| dc.description.abstract | Recently, Neri et al have introduced an efficient method to obtain endo-cavity
complexation and through-the-annulus threading of large calixarenes exploiting the
inducing effect of a weakly coordinating anion, tetrakis [3,5-bis (trifluoromethyl)
phenyl]borate (TFPB-).
In this PhD thesis this approach has been used for the synthesis of [2]rotaxanes,
which showed an unprecedented inversion of the wheel orientation.
Subsequently, it was extended to the synthesis of pseudo[3]rotaxane systems in
which two calix[6]arene macrocycles are threaded by a bis(benzylalkylammonium) axle.
Because of the three-dimensional nonsymmetrical nature of the calix[6]arene wheels, in
these instances three sequence stereoisomers could be obtained, which were termed as headto-
head (H,H), head-to-tail (H,T) and tail-to-tail (T,T).
Taking advantage of these systems, it was possible to obtain the stereoprogrammed
synthesis of the first examples of calixarene-based [3]rotaxane architectures. The base/acid
treatment demonstrated that these systems act as molecular shuttles, which move on a
nanometer scale level. The directionality of the threading and the observed high stereoselection have
enabled the synthesis of directional calix[6]arene-based catenane. All these aspects represent
interesting peculiar features of calixarene threading, which could be exploited for designing
molecular machines with new properties or functions | en_US |
