Self-assembling of supramolecular adducts by sulfonato-calix[4]arene and pyridinium gemini guests in neutral aqueous solution

- Sulfonato-calix[4]arene and gemini guests form capsular-like assemblies in water.
- The formation of the 1:1 host-guest complexes is always enthalpically driven.
- The driving forces for the capsular-like assemblies depend on guest size and shape.
- The formation of the capsular-like adducts is mostly driven by enthalpy gain.
- New insights for the design and development of molecular containers at neutral pH.

The formation of self-assembled structures triggered by pyridinium-based gemini guests in the presence of a sulfonato-calix[4]arene receptor has been thoroughly examined via isothermal titration calorimetry (ITC) in neutral aqueous solution. Data confirm the existence of a 1:1 host-guest complex, in which the guest is strongly bound to the host cavity, and the formation of a 2:1 capsular-like adduct. The splitting of the ΔG° term into the enthalpic and entropic contributions allowed to highlight the often opposing forces driving the encapsulation process which strongly depend on the size and shape of the gemini guest.