Calorimetric and spectroscopic investigations of interactions between cucurbituril Q7 and gemcitabine in aqueous solutions

Studies on the interactions between cucurbituril Q7 and gemcitabine (Gem) hydrochloride in water were carried out using isothermal titration calorimetry (ITC) and electrospray ionization–mass spectrometry (ESI-MS). According to ITC and ESI-MS, the formation of this complex occurs in both the solution containing excess gemcitabine and the solution containing excess cucurbituril Q7. ITC results confirm the formation of a thermodynamically stable supramolecular complex with stoichiometry 1:1. The inclusion mechanism of Gem inside the cucurbituril macromolecule is spontaneous ( $$\Delta G < 0$$ Δ G < 0 ). This process is exothermic ( $$\Delta H < 0$$ Δ H < 0 ) and is characterized by the loss of entropy ( $$\Delta S < 0$$ Δ S < 0 ).