Teresa Pierro

Fixed or Invertible Calixarene-Based Directional Shuttles

The first examples of rotaxanes based on calixarenes threaded by dialkylammonium ions, which also represent the first examples of calixarene-based molecular shuttles, are reported. The base/acid treatment demonstrated that these systems act as molecular shuttles, which move between three sites on the axle. When small OMe groups are appended at the calix[6]arene lower rim an unprecedented inversion of its shuttling direction is observed, which occurs through a cone-to-cone inversion of the macrocycle.

Paraquat guest-induced conformational templation of dicarboxylatocalixarenes

Proximal dicarboxylatocalix[4]arene 4 and distal dicarboxylatocalix[6]arene 5 have been synthesised in good yields and their complexation abilities towards dicationic paraquat guest 3 have been studied by NMR spectroscopy. Both hosts are able to complex 3 through an induced-fit mechanism, which originates from the conformational flexibility of calixarene macrocycle. A pH-dependent switching system was realised in which guest inclusion can be controlled through an acid/base external stimulus.