Fijs W. B. van Leeuwen

Multiple ionic interactions for noncovalent synthesis of molecular capsules in polar solvents

The formation and characterization of molecular capsules resulting from the self-assembly between oppositely charged (thia)calix[4]arenes in polar solvents like MeOH and MeOH–H2O are reported. The multiple ionic interactions allow the self-assembly of the complementary (thia)calix[4]arenes 1 and 2a–d into 1∶1 complexes as revealed by 1H NMR and mass spectrometry (ESI-MS). Isothermal titration calorimetry (ITC) was used to determine the association constants, which, depending on the ionic groups involved in the complexes, vary between 103 and 106 M−1. An X-ray structure of the assembly 1•2d was also obtained. Unlike in solution, in the solid state 1•2d forms a 1∶1 three-dimensional network in which 2d adopts a 1,2-alternate conformation.

Cation control on the synthesis of p-t-butylthiacalix[4](bis)crown ethers

Bridging of p-t-butylthiacalix[4]arene with ethylene glycol ditosylates gave diametrically bridged thiacalix[4]monocrowns-4 and -5, 1,2-alternate thiacalix[4]biscrowns-4 and -5 and 1,3-alternate thiacalix[4]biscrown-5, dependent on the metal carbonate used. They show excellent extraction ability towards Ag+ cations. The synthesis of novel diametrically and proximally substituted p-t-butylthiacalix[4](bis)crown ethers and their extraction behavior towards monovalent metal ions are presented.