The
nature of interactions between the neutral/protonated mitoxantrone
and the cucurbit[n]uril (n = 7,
8) host system was analyzed by employing density functional theory
calculations. A comparison between the inclusion complexes of CB[7]
and CB[8] shows various subtle differences in the complexation thermodynamics,
given as changes in the Gibbs energy. Doubly and quadruply charged
mitoxantrone (MX) molecules spontaneously form complexes in a water
solvent, which are modeled using the polarizable continuum model approach.
Both CB[7] and CB[8] complexes are stable as the geometry of the cavity
allows for electrostatic interactions between the charged MX arms
and the rim of the CB cavity. CB[8] also forms a stable complex with
two mitoxantrone molecules with their aromatic rings stacked inside
the cavity. Both CB[7] and CB[8] show properties that can be utilized
in drug delivery.