Where k is the Coulomb constant, qi is a partial charge of a cage atom, and d(grid,i) is the distance between the cage atom and the cavity grid point. The partial charges are determined using the electronegativity equalization method (EEM) implemented in Open Babel, a widely accepted and efficient procedure for deriving charge-based descriptors in QSAR studies. The cavity ESP is a valuable tool for identifying favorable interactions between hosts and polar guests. For example, by computing the ESP for a [Pd2L4] 4+ cage and 1,4-dicyanobenzene as a potential guest, one can easily visualize the complementarity of their ESPs, suggesting the formation of a strongly bound host-guest complex (Figure ). Negatively charged cages are relatively less common than positively charged ones. Nevertheless, we present an example of a purely organic cage, containing carboxylic groups, which results in a cavity with a negative ESP. This feature suggests that the cage can potentially encapsulate and stabilize positively charged guest molecules (Figure ).