A clip-like host that undergoes self-assembly and competitive guest-induced disassembly in water

Certain calix[4]arenes that are anionic and appended with a single hydrophobic substituent can self-assemble into homodimers in water. The unusual behaviours of these assemblies in water solutions are largely attributed to them being formed from like-charged building blocks. We report here a new entry into this series – a difunctionalized analog with two hydrophobic arms, a net – 3 charge on each monomer, and an overall U-shaped ‘clip’ topology. We use 1H NMR, 1-D DOSY and ITC to show that the new compound dimerizes in water but remains monomeric in organic solvents. Various cationic ammonium ion guests are able to drive dimer disassembly in favor of 1:1 host-guest complexes. The extent of competition is proportional to overall guest hydrophobicity.