Supramolecular Pathway Complexity of a Host‐Guest System Revealed in the Single‐Crystal Structural Snapshots

ABSTRACT

The host‐guest aqueous complexation gives rise to a library of crystal structures of distinct inclusion modes and solvation states, all assembled from p ‐sulfonato‐calix[4]arene as a host and p ‐amino‐benzamidine as a guest. Benefitting from single‐crystal X‐ray diffraction analysis and microscopic observation, we show that these host‐guest structures emerge progressively from kinetically trapped highly solvated assemblies to thermodynamically favored inclusion complexes as a function of time and concentration. The host‐guest system is also highly sensitive to solvent composition, as reflected in the alteration of ¹ H NMR spectra and crystallization behavior between water‐alcohol and purely aqueous solutions. The work illustrates how crystallization can serve as a structural probe of pathway‐dependent supramolecular maturation, enabling direct observation of kinetically and thermodynamically accessible assembly states in aqueous host‐guest systems.