In the SAMPL7 challenge, the host is not a classic cucurbituril, as instead of being a macrocycle, it is a clip-shaped molecule based on similar chemistry. Particularly, the host is an acyclic cucurbituril clip composed of a glycoluril trimer capped with aromatic triptycene sidewalls at both ends (here called TrimerTrip, as it is a trimer of glycoluril units with triptycenes), and four sulfonate solubilizing groups protruding out from the sidewalls (Figure ) . The sulfonate groups also enhance ion-ion interactions with cationic guests , which are typical cucurbituril binders. Acyclic CB[n]-type receptors often take on a C-shape due to their increase in flexibility . Experimentalists synthesized acyclic cucurbiturils with the idea to help increase the binding strength and capacity for different guests, including macrocyclic guests. Typically, CB[n]-guest complexes have very high affinity, especially for charged hydrophobic ammonium guests similar to those of the SAMPL7 challenge (Figure ). This high affinity is due to the presence of intracavity waters lacking a full complement of hydrogen bonds. The lack of hydrogen bonds is known to provide an enthalpic driving force for binding to macrocyclic CB complexes . In terms of CB[n]-guest complex interactions, the charged nitrogen group on guests interacts with oxygens from the carbonyl portal of the host. The latter contributes to limiting the number of poses that need to be considered , at least in cyclic hosts.