Supramolecular self-assembly between cucurbit[6]uril and 1-(2-hydroxyphenyl)piperazine hydrochloride

The interaction between 1-(2-hydroxyphenyl)piperazine (HPP) and cucurbit[6]uril (Q[6]) has been explored via 1 H NMR spectroscopy and X-ray crystallography. The results show that the guest molecule 1-(2-Hydroxyphenyl)piperazine hydrochloride is not encapsulated within the Q[6] cavity in both aqueous solution and the solid state. Instead, it resides at the portal of Q[6], forming a highly stable exclusion complex, designated HPP 2 @Q[6]. Notably, ion-dipole and hydrogen-bonding interactions play key roles in stabilizing this complex.